NATIVE MICE and RATS BILL BREED and FRED FORD NATIVE MICE and RATS Photos Courtesy Jiri Lochman,Transparencies Lochman

AUSTRALIAN NATURAL HISTORY SERIES AUSTRALIAN NATURAL HISTORY SERIES

NATIVE MICE AND RATS BILL BREED AND FRED FORD NATIVE MICE AND RATS Photos courtesy Jiri Lochman,Transparencies Lochman

Australia’s native rodents are the most ecologically diverse family of Australian mammals. There are about 60 living species – all within the subfamily Murinae – representing around 25 per cent of all species of Australian mammals.They range in size from the very small delicate mouse to the highly specialised, arid-adapted hopping mouse, the large tree rat and the carnivorous water rat. Native Mice and Rats describes the evolution and ecology of this much-neglected group of animals. It details the diversity of their reproductive biology, their dietary adaptations and social behaviour. The book also includes information on rodent parasites and diseases, and concludes by outlining the changes in distribution of the various species since the arrival of Europeans as well as current conservation programs.

Bill Breed is an Associate Professor at The University of Adelaide. He has focused his research on the reproductive biology of Australian native mammals, in particular native rodents and dasyurid marsupials. Recently he has extended his studies to include rodents of Asia and Africa. Fred Ford has trapped and studied native rats and mice across much of northern Australia and south-eastern New South Wales. He currently works for the CSIRO Australian National Wildlife Collection.

BILL BREED AND FRED FORD NATIVE MICE AND RATS

Native Mice 4thpp.indd i 15/11/07 2:22:35 PM Native Mice 4thpp.indd ii 15/11/07 2:22:36 PM AUSTRALIAN NATURAL HISTORY SERIES NATIVE MICE AND RATS

BILL BREED AND FRED FORD

Native Mice 4thpp.indd iii 15/11/07 2:22:37 PM © Bill Breed and Fred Ford 2007 All rights reserved. Except under the conditions described in the Australian Copyright Act 1968 and subsequent amendments, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, duplicating or otherwise, without the prior permission of the copyright owner. Contact CSIRO PUBLISHING for all permission requests.

National Library of Australia Cataloguing-in-Publication entry Breed, Bill. Native mice and rats. Bibliography. Includes index. ISBN 9780643091665 (pbk.). 1. Mice – Australia. 2. Rats – Australia. I. Ford, Fred. II. Title. (Series : Australian natural history series).

599.35

Published by CSIRO PUBLISHING 150 Oxford Street (PO Box 1139) Collingwood VIC 3066 Australia

Telephone: +61 3 9662 7666 Local call: 1300 788 000 (Australia only) Fax: +61 3 9662 7555 Email: [email protected] Web site: www.publish.csiro.au

Front cover: Spinifex hopping mouse emerging from burrow Back cover (clockwise from top left): Golden-backed tree rat, delicate mouse, western pebble-mound mouse, desert mouse (photos by Jiri Lochman/Lochman Transparencies)

Set in 10.5/14 Palatino Cover and text design by James Kelly Typeset by Palmer Higgs Printed in Australia by Ligare

Native Mice 4thpp.indd iv 15/11/07 2:22:37 PM CONTENTS

Preface and acknowledgements vii

1 Introduction 1

2 Diversity 15

3 Distribution 39

4 Origins and evolution 55

5 Reproduction 87

6 Diet and gastrointestinal tract 101

7 Populations and communities 115

8 Social organisation and behaviour 125

9 Parasites and disease (by Andrew Breed) 139

10 Conservation 149

Glossary 164

Bibliography 167

Index 177

Native Mice 4thpp.indd v 15/11/07 2:22:38 PM Native Mice 4thpp.indd vi 15/11/07 2:22:38 PM PREFACE AND ACKNOWLEDGEMENTS

This book has been written by two biologists with very different backgrounds. Both of us, however, share a love of the natural world and have studied the biology of Australia’s native mice and rats extensively. We have both become fascinated by their diversity and the evolutionary relationships between the species within this group. The book is the product of many years’ work and has had a gestation period of over six years. It is an attempt to summarise the information obtained about this group of mammals during the last 25 or so years. There are around 60 species of living rodents in Australia today. At least seven others have become extinct since the arrival of Europeans. It is perhaps surprising that the native mice and rats seem to have suffered as much, if not more, than the marsupials during this time. One would have thought that by now the taxonomy of the group would have been thoroughly worked out, but this is not the case. Even the two authors of this book had a bit of a tussle agreeing on a mutually acceptable classification system. Almost everyone who has worked on the evolutionary biology of these rodents agrees that there are two major groups: one, an ancient group that has been in Australia for at least four million years and the other a more recent group, the ancestors of which probably arrived here one to two million years ago. However the relationships between and within the members of the older group in particular are currently in a state of flux. In Chapter 1 we briefly indicate the different taxonomies in the hope that anyone familiar with any particular classification system will be able to relate this to the others as well as to the one we have adopted. Not only is the taxonomy of the major groups not universally agreed upon but, at the present time, there are several species still awaiting formal description. For instance, the delicate mouse, Pseudomys delicatulus, one of the first native rodents to be discovered and which was illustrated by John Gould in his Mammals of Australia in 1860, turns out to be two or possibly three species. Similarly, whether the sole Australian species of prehensile-tailed rat is the same species as one of the many species in Papua New Guinea is not known at this stage. There is also a species of native rat in the genus Rattus that occurs in central Queensland which has still has not been formally described. In spite of these ‘unknowns’, it is clear that we do know far more about the native mice and rats of this country than was the case when the last book, The Rodents of Australia, by Chris Watts and Heather Aslin, was written on this topic 25 years ago. In our book, we focus on information obtained since

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that time. Clearly a book of this nature, covering such a broad field, will reflect the interests of the authors. We have tried to cover as much as possible about the biology of these animals, but there will be some areas that we have inadvertently neglected. One area of debate between us was whether or not to mention individual research workers by name who we believe have made a substantial contribution to the field. After some discussion, we agreed not to do so, although at the end of the book we give a reasonably extensive list of references for those who wish for more detailed information. In the writing of this book we also debated whether to use the formal Latin names of the individual species or the English names. In an attempt to make the text easier to read for the non-specialist we mostly opted for the latter but we included the Latin names together with the English names in Chapters 1 and 2. A constantly recurring theme in this book is that, despite the Old Endemic rodents arriving in this country far more recently than marsupials or monotremes, there is much diversity in their body form, in various aspects of their ecology, behaviour and social organisation, the food they eat and the associated dental morphology and the proportions of the rest of the gastro-intestinal tract, as well as their reproductive biology. In fact, diversity in body form and function seems to be the hallmark of this Old Endemic group of mice and rats. Rodents clearly have a very different origin from that of the two other groups of land-dwelling mammals, the marsupials and monotremes. They entered Australia from Asia and were the only land mammals to manage the sea crossing from South-East Asia until humans followed several million years later. Since the rodents arrived on this landmass they have adapted to most of the continent’s natural environments and contribute a very important component of biodiversity that complements, rather than clashes, with the older marsupial and monotreme species. Australian native rodents do not adapt well to disturbance of their habitats and unlike rodents in some other parts of the world, they have not become pest species except for a few localised cases. It is the introduced house mouse, not a native rodent, which causes millions of dollars’ damage in the grain-growing areas of southern Australia. Only in the sugar cane fields of north Queensland have any species of native rodent caused any major economic loss. This contrasts markedly with the damage caused by native rodents of South-East Asia and, to a lesser extent, Africa.

viii

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If this book enhances awareness of this relatively little known group of mammals that makes up around 25 per cent of all mammal species of Australia, and this increased knowledge results in a greater effort to conserve what is left of this important native mammal group, then we will be well pleased and feel that one of our main aims has been achieved. A book of this nature would not have been possible without the help of a number of people. In particular, we would like to thank Andrew Breed of The University of Queensland for writing Chapter 9 on parasites and disease and Mike Kokkin of The University of South Australia for allowing us to reproduce his unpublished diagrams of the gastrointestinal tracts. Alice MacDougall generously contributed some of the line drawings of rodent genera. Many colleagues at The University of Adelaide helped in a variety of ways. In particular, we would like to thank Chris Leigh and Tavik Morgenstern of the Discipline of Anatomical Sciences, Faculty of Health Sciences; Peter Self and Lyn Waterhouse of Adelaide Microscopy for assistance with the microscopy; numerous honours and PhD students of The University of Adelaide, as well as Brian Miller, and Matthew and Martin Breed, who acted as assistants on various field trips. Over the years a number of specimens were kindly given to us by Chris Watts and Peter Baverstock who, at that time, worked at the field station of the Institute of Medical and Veterinary Science, at Gilles Plains. To all these individuals we extend our sincere thanks. The Australian Museum and CSIRO Australian National Wildlife Collection kindly allowed us access to their rodent collections and Steve Van Dyck of The Queensland Museum and David Stemmer of The South Australian Museum kindly loaned us skeletal material. In addition we thank Melissa Bauer, Peter Bird, Ron Sinclair, Mike Thompson, Clive Crouch, Steve Morton, Mark Adams, Ben Luxton, Jenny Washington, Eleanor Peirce, Helen Owens and John Reid for assisting us in various ways. Several people have provided photographs that we have included in this book. In particular we would like to thank Tony Robinson, Peter Canty, Jiri Lochman, Linda Broome, Uli Kloecker, Jim Forrest, Steve Doyle, Dave Taggart, Libby Olds, Jim Parke and Mike Cermak for the photographs they provided. We would also like to thank the Gomboc Gallery for giving us permission to include the drawings by Ella Fry. Thanks also to James Menzies, Robert Brandle and Ian Hume who critically read various chapters. We should especially like to extend our

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sincere thanks to our long-suffering partners: Esther Breed, who typed the first drafts of the book and who has meticulously read and commented upon every chapter, and Karen Ford who put up with more cussing over problematic passages than was necessary. To our reviewers, Ken Aplin and Chris Watts, we also extend out deepest gratitude, and to Terry Dawson who provided comments on an early version of the manuscript. Finally we thank Nick Alexander for his patience over the years and his encouragement to us to keep going to the end, as various deadlines have come and gone.

Bill Breed Fred Ford

Native Mice 4thpp.indd x 15/11/07 2:22:39 PM 1 INTRODUCTION

he most conspicuous native mammals of Australia are, of course, the Tmarsupials. Less well known is the fact that around half of all species of Australian mammals are not marsupials but belong to that other large group of living mammals that includes ourselves – the eutherians or so- called placental mammals. Many of the species of eutherian mammals in Australia are native rats and mice that belong to the Order Rodentia – a group that makes up around 40 per cent of all mammalian species worldwide. The remainder of the Australian eutherians is made up of bats, together with an assortment of seals, whales and dolphins. Despite the fact that two species of native rodents – the water rat and the bush rat – live within, or close to, our city boundaries, there is a general lack of awareness about these native mammal species. Hedley Finlayson, a chemist working at The University of Adelaide, who was also Honorary Curator of mammals at the South Australian museum, pioneered studies on the natural history of mammals in central Australia in the 1930s. In his 1945 book, The Red Centre, he states:

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… there is a widespread idea amongst Australians that all the ‘native’ mammals are marsupials. But nowhere in the country can that opinion be proved more fallacious than in the Centre, where the indigenous rodents vastly predominate numerically over the marsupials …

As well as the two major groups of living mammals, marsupials and eutherians, Australia is also home to the only two lineages of living monotremes, the platypus and echidna. It thus has a unique and diverse mammalian fauna that is not matched by any other landmass apart from New Guinea. The origins of eutherian mammals in Australia are dramatically different from those of monotremes and marsupials. Whereas the ancestors of modern marsupials and monotremes have probably been in Australia for over 100 million years, as they were part of the original mammalian fauna of the ancient southern continent Gondwana, the native mice and rats originated in Asia and arrived in Australia much more recently from the north. Unlike the house mouse, the black rat and the brown (or Norway) rat, which were introduced by Europeans between 200 and 300 years ago, the ances tors of the Australian native mice and rats entered Australia long before humans arrived with one or more groups having been here for at least four million years. Although many species of native rodents are now restricted in their distribution, or have even recently become extinct, knowledge of their biology has increased considerably in recent years. Since 1981 when the last book on native mice and rats, The Rodents of Australia, by Chris Watts and Heather Aslin was published, we have learnt much about the distribution and abundance of these animals, as well as their general biology. The relationships between the species, and to mice and rats occurring outside Australia, are also better understood. Furthermore, several new species of Australian rodents have been recognised and described in the recent past. In this book we present a general account of the diverse biology and natural history of Australian native mice and rats, with par ticular emphasis on the data obtained over the last 25 years.

What are the Australian native mice and rats? The native mice and rats of Australia are very different from the small native marsupials which are sometimes referred to as ‘marsupial mice’,

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a term which is generally applied to species of marsupials in the genus Antechinus. However, the body shape and way of life of Antechinus is much more like that of a large shrew than it is to a mouse and, like a shrew, it is insectivorous. In contrast to these species, all the native Australian mice and rats have highly specialised teeth which are very different in form from those of small marsupials as well as other groups of eutherian mammals. Nevertheless, mice and rats exhibit a considerable diversity in their diet which, in the Australian species, ranges from seed, grain, grass, fruit, insects to even fish or meat. These Australian mice and rats consequently exhibit a wide variety of ways of life, and can thus be found in various habitats ranging from freshwater swamps, riverbanks, grasslands and forests to deserts, alpine regions, the seashore and mangroves. In spite of the native Australian mice and rats exhibiting numerous body forms (see illustrations), they are all similar to each other in the general arrangement of their teeth – with all having only two upper and two lower front teeth or incisors and, in this respect, they differ from most other orders of mammals. Their incisors have a hard layer of enamel on their front surface (see Chapter 6) which often has a distinctive orange or yellow colour. In the introduced house mouse the incisors have a characteristic notch (see Figure 1.1), but this is not present in the native species. Apart from their dentition, rodent skulls are typical of small mammals in that they have a prominent rostrum, or snout, behind which there is a bulbous brain case.

Diversity of Australian native mice and rats Within the Order Rodentia there are two suborders: the Hystricognathi and the Sciurognathi. The Hystricognathi are largely South American and include guinea pigs, agoutis, maras and their allies as well as porcupines and a few other African species. The other Suborder, the Sciurognathi, is comprised of several major groups including squirrels, marmots, prairie dogs, beavers, kangaroo rats and jerboas. By far the largest family within this suborder is the Family Muridae which includes the Old World mice and rats, as well as the gerbils of Africa and southern Asia, with the New World rats and mice, such as voles, lemmings and deer mice, being placed in the Family Cricetidae. There are three subfamilies within the Muridae, the largest of which is the Murinae which includes all the Australian native mice and rats. The Murinae also includes many species that occur

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Figure 1.1 Part of house mouse (a) and western chestnut mouse (b) skulls and teeth. Note the notch on the house mouse (arrow), but not on the chestnut mouse, incisor – a diagnostic feature used in the field. I = incisor; M1, M2 and M3 = molars; ZA = zygomatic arch. The gap between the incisors and molars is called a diastema.

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in southern Asia, the Philippines, Sulawesi, as well as Africa and Europe. In Australia, the 60 or so species of murine rodents range in size from the delicate mouse – with an adult body mass of about 6 g – to the water rat and black-footed tree rat which can weigh up to nearly 1 kg. Some species appear to lack obviously specialised morphological or physiological adaptations whereas others, such as the aquatic water rats and desert- living hopping mice, exhibit a variety of morphological and physiological adaptations to their particular way of life. The Australian native mice and rats are currently composed of 13 genera. This generic diversity is matched by the diversity of habitats in which they occur. For example, aquatic and tidal habitats are the home of water rats (Hydromys) and water mice (Xeromys); rainforests of North Queensland are inhabited by a species of prehensile-tailed rat (Pogonomys) and several species of mosaic-tailed rats (Melomys and Uromys); rocky outcrops in northern Australia and a small region of Central Australia are the home of five species of rock-rats (Zyzomys); eucalypt woodlands of northern Australia are inhabited by large tree rats (Conilurus and Mesembriomys); and deserts and semi-desert regions harbour terrestrial species such as hopping mice (Notomys), short-tailed mice (Leggadina), stick-nest rats (Leporillus), as well as various species of small native mice in the genus Pseudomys. Even the alpine region of south-eastern Australia has a species of specialised native rodent, the broad-toothed rat (Mastacomys) that lives under the snow in winter. The taxonomy of the Australian mice and rats has been an area of controversy, and even today it is still not universally agreed upon. There appear to be five natural groupings of native mice and rats that belong to two major groups (see Table 1.1). They are:

1 The Australo-Papuan Old Endemics This group consists of many related species that are common in both New Guinea and Australia. It includes the Australian Old Endemics together with three other groupings whose closest relatives occur in New Guinea. The groupings are:

• The Australian Old Endemics or ‘Pseudomys Group’: around 50 species in at least seven genera that range from small native mice and specialised hopping mice to large tree rats (grouping 1a).

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Mitchell’s hopping mouse. Drawing by Ella Fry.

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• The mosaic-tailed rats or ‘Uromys Group’: two genera that include melomys and the white-tailed rats (grouping 1b). • The water rats or ‘Hydromys Group’: a single species of water rat and a water mouse (grouping 1c). • The New Guinean Old Endemics or ‘Pogonomys Group’: a single species occurs in Australia – the prehensile-tailed rat (grouping 1d). All other members of this grouping occur in New Guinea.

2 The Australo-Papuan New Endemics • Native Rattus or true rats: eight species of native rats all in the genus Rattus, with several others in New Guinea. Two other species have been introduced by Europeans.

The Australo-Papuan Old Endemics have sometimes been given a subfamily name the ‘Hydromyinae’. Within this subfamily three tribes have been named. These are the ‘Conilurini’ or conilurine rodents, for the Australian Old Endemics; the ‘Uromyini’, for the mosaic-tailed rats; and the ‘Hydromyini’, for the water rats. A fourth tribal name ‘Anisomyini’ has been proposed for the New Guinean Old Endemics as well as the prehensile-tailed rat from north Queensland. Recent molecular work on amino acid sequences of albumin and the nucleotide sequences of several nuclear and mitochondrial genes has questioned whether some of these groupings are natural associations of species. Thus, at the present time, it is probably best to abandon the formal tribal and subfamily names. In the third edition of Don Wilson and DeeAnn Reeder’s Mammal Species of the World published in 2005, Guy Musser and Mike Carleton include an extensive account of the murid rodents in which the Old World mice and rats have been placed in a series of ‘divisions’. The Australian Old Endemics are allocated to a ‘Pseudomys division’, the mosaic-tailed rats to a ‘Melomys division’, the Rattus species to a ‘Rattus division’, the water rat and its New Guinea close relatives to a ‘Hydromys division’, the water mouse and its close New Guinea relatives to a ‘Xeromys division’, and the prehensile-tailed rat and its close relatives to a ‘Pogonomys division’. Only time will tell whether or not these divisions become generally accepted. In this book, however, we will use the informal groupings listed in Table 1.1.

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Table 1.1 Species and genera of Australian mice and rats (Subfamily Murinae). 1 The Australo-Papuan Old Endemics 1a The Australian Old Endemics or ‘Pseudomys Group’ Rabbit rats White-footed rabbit rat Conilurus albipes (EX) Brush-tailed rabbit rat Conilurus penicillatus Short-tailed mice Desert short-tailed mouse Leggadina forresti Tropical short-tailed mouse Leggadina lakedownensis Stick-nest rats Lesser stick-nest rat Leporillus apicalis (EX) Greater stick-nest rat Leporillus conditor Tree rats Black-footed tree rat Mesembriomys gouldii Golden-backed tree rat Mesembriomys macrurus Hopping mice Spinifex hopping mouse Notomys alexis Short-tailed hopping mouse Notomys amplus (EX) Northern hopping mouse Notomys aquilo Fawn hopping mouse Notomys cervinus Dusky hopping mouse Notomys fuscus Long-tailed hopping mouse Notomys longicaudatus (EX) Big-eared hopping mouse Notomys macrotis (EX) Mitchell’s hopping mouse Notomys mitchelli Darling Downs hopping mouse Notomys mordax (EX) Broad-cheeked hopping mouse Notomys species (EX) ‘False mice’ (Pseudomys subgroup 1) Plains mouse Pseudomys australis Shark Bay mouse Pseudomys fieldi (including P. praeconis) Long-tailed mouse Pseudomys higginsi Long-eared mouse Pseudomys auritus (EX) ‘Velvet mice’ (Pseudomys subgroup 2) Ash-grey mouse Pseudomys albocinereus Silky mouse Pseudomys apodemoides Smoky mouse Pseudomys fumeus Blue-grey mouse Pseudomys glaucus (EX?) ‘Delicate mice’ (Pseudomys subgroup 3) Bolam’s mouse Pseudomys bolami Delicate mouse Pseudomys delicatulus (incl. P. pilligaensis) Sandy inland mouse Pseudomys hermannsburgensis New Holland mouse Pseudomys novaehollandiae North-western delicate mouse Pseudomys sp. (undescribed) Broad-toothed rat and chestnut mice (Pseudomys subgroup 4) Broad-toothed rat Mastacomys fuscus Eastern chestnut mouse Pseudomys gracilicaudatus Western chestnut mouse Pseudomys nanus Pebble-mound mice (Pseudomys subgroup 5) Kakadu pebble-mound mouse Pseudomys calabyi Western pebble-mound mouse Pseudomys chapmani Central pebble-mound mouse Pseudomys johnsoni (includes P. laborifex) Eastern pebble-mound mouse Pseudomys patrius

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1a The Australian Old Endemics (contd.) ‘Grizzled mice’ (Pseudomys subgroup 6) Desert mouse Pseudomys desertor Heath mouse Pseudomys shortridgei Other native mice (Pseudomys subgroup 7) Western mouse Pseudomys occidentalis Hastings River mouse Pseudomys oralis Gould’s mouse Pseudomys gouldii (EX) Rock-rats Common rock-rat Zyzomys argurus Arnhem Land rock-rat Zyzomys maini Carpentarian rock-rat Zyzomys palatalis Central rock-rat Zyzomys pedunculatus Kimberley rock-rat Zyzomys woodwardi 1b Mosaic-tailed rats or ‘Uromys Group’ Melomys Grassland melomys Melomys burtoni Fawn-footed melomys Melomys cervinipes ‘Grassland’ melomys Melomys lutillus Cape York melomys Melomys capensis Bramble Cay melomys Melomys rubicola White-tailed rats Giant white-tailed rat Uromys caudimaculatus Masked white-tailed rat Uromys hadrourus 1c Water rats or ‘Hydromys Group’ Water rat Water rat Hydromys chrysogaster Water mouse or false water rat Water mouse Xeromys myoides 1d The New Guinean Old Endemics or ‘Pogonomys Group’ Prehensile-tailed rat Prehensile-tailed rat (or tree mouse) Pogonomys sp. (mollipilosus?)

2 The Australo-Papuan New Endemics Native Rattus or True rats Dusky rat Rattus colletti Bush rat Rattus fuscipes Cape York rat Rattus leucopus Swamp rat Rattus lutreolus Canefield rat Rattus sordidus Undescribed species Rattus sp. Pale field rat Rattus tunneyi Long-haired rat Rattus villosissimus

3 Introduced Species House mouse Mus musculus Pacific rat Rattus exulans Black rat Rattus rattus Brown rat Rattus norvegicus Note: EX = extinct.

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Early records of Australian mice and rats Although it was the diversity of marsupials and oddities such as the platypus that largely held the fascination of European biologists in Australia in the 19th century, native mice and rats sometimes made lasting impressions on the early explorers. One of the first Europeans to record observations of native rodents was Thomas Mitchell, who carried out expeditions to inland Victoria between the years 1831 and 1836. He collected four species of native mice and rats which were deposited in the Australian Museum. One of these, Dipus (= Notomys) mitchelli, was named after him by Ogilby in 1837. In 1836 when Charles Darwin, aboard the Beagle, visited King George Sound in Western Australia, he collected a species of native rat, the bush rat, Rattus fuscipes. Between 1856 and 1857 Krefft found ‘large colonies of stick-nest rats’ along the River Murray at the Murray-Darling junction and ‘often fetched 8–10 of them from a tree hollow’. Krefft wrote that he kept a number in captivity and ‘many which had escaped would return to join my frugal supper at night, and help themselves to damper especially …’. Krefft’s curiosity led him to eat one of these animals, which he seemingly enjoyed, describing the flavour of the flesh as ‘excellent’. In 1864 John Gould published Mammals of Australia in which he included various native mice and rats, many specimens of which had been collected by John Gilbert. In all, 27 rodent species were described ranging from the four colour phases of the ‘beaver rat’ (water rat), to the diminutive ‘delicate-coloured mouse’ (delicate mouse) (see page 11). Charles Sturt, in his experiences of native rats and mice, wrote of the fawn hopping mouse, Hapalotis (Notomys) cervinus, which he described as a ‘jerboa-like rodent’: On the 20th we found ourselves on latitude 29˚ 6’ and halted on one of those clear patches on which the rain-water lodges, but it had dried up and there was only a little for our use in a small gutter not far distant. Whilst we were here camped a little Jerboa was chased by the dogs into a hole close to the drays which, with four others, we succeeded in capturing. This beautiful little animal burrows in the ground like a mouse, but their habitations have several passages leading straight, like the radii of a circle, to a common centre, to which a shaft is sunk from above …

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The delicate mouse, from Gould’s Mammals of Australia.

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Another species of note observed by Sturt was one he called a ‘building Hapalotis’ (the stick-nest rat, Leporillus), which he found inhabiting ‘the brushes of the Darling but was not found beyond latitude 30°’. He noted that it built a nest of … small sticks varying in length from three to eight inches … arranged in a most systematic manner so as to form a compact cone like a beehive, about four feet in diameter and three feet high; those at the foundation are so disposed as to form a compact fl ooring, and the entire fabric is so fi rm as almost to defy destruction except by fi re …

In the early descriptions of native rodents, there were occasional observations of huge numbers of animals that made a marked impression. Professor J B Cleland, who in 1918 summarised some of the early reports of rodents, cited a communication from a Mr John Bagot … In 1887 I was witness to an enormous migration of rats, thousands of millions, I should say. In that year we were building the railway … round the south shore of Lake Eyre. We were camped in tents a mile or two from the dry lake-bed … Suddenly, before precautions could be taken, a plague of rats was upon us, and in a very brief space a thousand pounds worth of provisions, tents and other commodities were destroyed. The rats had come from the north, from the great dried-up river beds of the Finke …

Also in the same article Professor Cleland quotes a Mr Palmer in 1885 as having recorded … the plague of rats increased to an extent that would scarcely be credible. They covered the plains in every direction; when riding at night they could be heard squeaking everywhere, ﬁ ghting with each other; they swarmed into the huts and gnawed everything they could get at. Flour, meat and leather had to be stored in galvanised iron rooms or safes, built expressly for the purpose. When camping out every article had to be hung in a tree, and the hobbles, made of green hide, have been known to be gnawed off horses’ feet during the night … If a hundred were killed around the hut at night there appeared no diminution to the number of visitors on the following

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night, and for months in succession the same slaughter could be kept up …

Other early explorers were struck more by the beauty and agility of the native rodents than by their abundance. Waite, writing in 1915, says of the hopping mouse … … this wonderful little rat was seen more than once at midday in the mulga scrub. When alarmed it places its tail over its back and head and moves on its hind legs only. When in full ﬂ ight it is difﬁ cult to ascertain what the moving object really is, appearing as little more than a blur.

Mice and rats had probably been an important source of food and culture for Aboriginal peoples for thousands of years. This is reflected in an account by Charles Sturt in 1845 … These wanderers of the desert had their bags full of jerboas which they had captured in the hills. They could not indeed have had less than from 150 to 200 of these beautiful little animals, so numerous are they in the sand hills, but it would appear that the natives can only go in pursuit of them after a fall of rain, such as that we had experienced … our friends cooked all they had in hot sand, and devoured their entire fur, skin, entrails and all, only breaking away the under jaw and nipping off the tail with their teeth. They absolutely managed before sunset to ﬁ nish their whole stock, and then took their departure having, I suppose, gratiﬁ ed both their appetite and their curiosity.

For a brief time, the early explorers were able to experience a continent unaltered by the onslaught of introduced exotic species and destructive land-use practices that overcame much of the native fauna during the latter half of the 19th and early 20th century. In the following two chapters we detail the diversity and regional distribution of the native rats and mice evident today, and reflect upon what the natural situation might have been like when Europeans first arrived in Australia.

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The golden-backed tree rat. Drawing by Ella Fry.

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efore the arrival of Europeans there were at least 70 species of native Bmice and rats in Australia. Since then at least seven species have become extinct, all of which were members of the Australian Old Endemic group. In addition, the ranges of a large number of other species have become greatly reduced with several species now listed as endangered (see Chapter 10). Some of the extinctions and range contractions took place in the arid zone in the 1800s and early 1900s, far from European settlements, and our knowledge of the biology of these species is, as a result, almost nonexistent. However, other species thought to be extinct have subsequently been ‘rediscovered’ and capture of species well outside their previously known ranges still occurs occasionally, particularly in northern Australia. Apart from the native Australian mice and rats, there are three species that have been introduced into Australia by Europeans over the last 200 to 300 years – the house mouse, black rat and brown (or Norway) rat. In addition, the Pacific rat, that the Polynesians introduced to various Pacific islands, is also present on a few islands administered by Australia. Several other species of rodent have occasionally been introduced into this country,

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including domestic guinea pigs and palm squirrels, but none of them has become established in the wild. In this book we largely use common names rather than Latin or scientific names for the various species. In a few cases over the years more than one common name has been used for the same species, or the common name used for a species in this country is also applied to other distantly related species elsewhere. In general, we adopt the names used by Peter Menkhorst and Frank Knight in their book A Field Guide to Mammals of Australia published in 2001. While there are currently 13 recognised native Australian rodent genera, we outline 19 subgroups of species that we believe roughly equate to genera. The extra subgroups are all currently considered members of the large native rodent genus Pseudomys. Some, such as the distinctive pebble-mound mice, are clearly deserving of formal description at the generic level. Other subgroups are not so clearly defined and membership of each is still not fully resolved. Where a common name is established for a subgroup, we use that name and provide it in inverted commas. The presumed natural distributions of each species are shown although most species do not occupy all of their range due to recent reductions in distribution (see Chapters 3 and 10).

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Rabbit rats

White-footed rabbit rat Conilurus albipes (EX) (~200–300 g) Brush-tailed rabbit rat Conilurus penicillatus (100–200 g)

Brush-tailed rabbit rat

White-footed rabbit rat (EX)

The rabbit rats have large ears and very long, brush-tipped tails. Little is known of the white-footed rabbit rat as it disappeared from south-eastern Australia less than half a century after European colonisation. The brush- tailed rabbit rat now occurs on the mainland only in a small area of Kakadu National Park and on Coburg Peninsula in the Northern Territory and near coastal areas in the northern Kimberley. It is also present on a few islands off the northern coast. These animals mainly occur in tall open eucalypt forest and are dependent on tree hollows and logs for shelter thus making this species vulnerable to bush fires and land clearing (see Chapter 10). It is one of two members of the Australian Old Endemic group recorded from southern New Guinea.

NNativeative MiceMice 4thpp.indd4thpp.indd 2727 113/3/083/3/08 1:48:091:48:09 PMPM Native mice and rats

Short-tailed mice

Desert short-tailed mouse Leggadina forresti (~20 g) Tropical short-tailed mouse Leggadina lakedownensis (~18 g)

Tropical short-tailed mouse

Desert short-tailed mouse

The two species of short-tailed mice are both sparsely distributed throughout their ranges. They are characterised by having a very short tail; they are grey-brown above and white below with short, rounded ears, and a broad blunt muzzle. The desert short-tailed mouse is typically a species of the central arid zone, while the tropical short-tailed mouse occurs in tropical savannahs across the north of the country as well as in the Pilbara region. There is also a distinctive larger form of tropical short-tailed mouse on Thevenard Island off the coast of Western Australia (arrow) which may be adversely affected as a result of competition from the recent introduction of the house mouse (see Chapter 10). In the past, short-tailed mice have been described as members of the ‘delicate mice’ subgroup, but are now known to be a very distinct lineage (see Chapter 4).

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Stick-nest rats

Lesser stick-nest rat Leporillus apicalis (EX) (~120–150 g) Greater stick-nest rat Leporillus conditor (350 g)

Lesser stick-nest rat (EX) Greater and Lesser stick-nest rat

Stick-nest rats resemble rabbit rats in size and have blunt noses, large ears and sleek body fur. The most distinctive feature of these animals is their building of stick nests in a similar fashion to the wood rats (Neotoma spp.) of North America (see Chapter 8). All mainland populations of the two species of stick-nest rats appear to have become extinct over the last 200 or so years, with the last known record of the lesser stick-nest rat being in 1933. However, the greater stick-nest rat, which is the larger of the two species, has survived on Franklin Island in the Great Australian Bight off the coast of South Australia (arrow). The demise of the stick-nest rat species on the mainland means their natural distributions have to be reconstructed from sub-fossil remains and early records. The remains of stick nests built by these rats occur in caves and rock overhangs across a wide region of the southern arid and semi-arid zone. The sticks are often glued together by ‘cave bitumen’ or ‘amberat’ which is a product of faeces and urine that solidifies to form a resin-like material that can last for thousands of years. This amberat together with the cave middens of the stick-nest rats has proved valuable in reconstructing past environments based on small plant fragments and pollen grains trapped within it.

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Tree rats

Black-footed tree rat Mesembriomys gouldii (~720 g) Golden-backed tree rat Mesembriomys macrurus (~270 g)

Black-footed tree rat

Golden-backed tree rat

Both tree rat species inhabit tropical savannah woodland. The black- footed tree rat is by far the largest member of the Australian Old Endemic group and may be encountered scavenging through camp sites in Kakadu National Park. It also occurs on Melville Island where it might be in com petition with brush-tail possums for tree holes. Both tree rat species seem to have undergone range contraction in recent times with the north-west Kimberley being the present stronghold of the golden-backed tree rat where it also occurs on several off-shore islands. There are no recent confirmed sightings from the Northern Territory of this species (see Chapter 10). Tails of both species are striking due to their length and brushed tips with long hairs.

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Hopping mice

Spinifex hopping mouse Notomys alexis (~35 g) Short-tailed hopping mouse Notomys amplus (EX) (~100 g) Northern hopping mouse Notomys aquilo (~40 g) Fawn hopping mouse Notomys cervinus (~35 g) Dusky hopping mouse Notomys fuscus (~35 g) Long-tailed hopping mouse Notomys longicaudatus (EX) (~100 g) Big-eared hopping mouse Notomys macrotis (EX) Mitchell’s hopping mouse Notomys mitchelli (~50 g) Darling Downs hopping mouse Notomys mordax (EX) Broad-cheeked hopping mouse Notomys sp. (EX)

Northern hopping mouse

Long-tailed hopping mouse

Short-tailed and Spinifex hopping mouse y Long-tailed hopping mice k s u e D ic d n m g a n in Big-eared p w p Darling Downs a o hopping mouse Broad-cheeked hopping mouse F Mitchell’s hopping h hopping mouse mouse

During the day, hopping mice live in deep burrows where they make a nest chamber with leaves and other plant material. Vertical shafts lead from the horizontal tunnels to the surface. Hopping mice move on all fours when travelling slowly but hop on their hind feet when travelling fast (see page 100). Their morphological and physiological adaptations resemble desert-living, arid specialist rodents of Africa, Asia and North America (see Chapter 4) in that they have elongated hind feet with

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reduced number of sole-pads, a long brush-tipped tail, large ears and eyes. Most hopping mice species live predominantly on stabilised sand dunes, but the fawn hopping mouse, which occurs to the north-east of Lake Eyre, is present mainly on gibber plains and clay pans, although it may predominantly burrow on small islands of sandy soil. This species also lacks a throat pouch that occurs in the other extant species, the secretions of which may be used for territorial marking. Spinifex hopping mice are widespread throughout the arid zone of central and western Australia, whereas the dusky hopping mouse occurs in a relatively small area to the east and north of Lake Eyre, largely on sand hills with canegrass. Several related species of hopping mice have become extinct over the last 200 years or so. The diversity of hopping mice is highest in the Lake Eyre Basin where the spinifex, dusky and fawn hopping mice all occur. The northern hopping mouse inhabits, or inhabited, tropical sand dunes in the Top End and is found on Groote Eylandt, whereas Mitchell’s hopping mouse, which is the largest of the extant species, occurs in the mallee regions of southern Australia. Most species have a very distinctive reproductive anatomy (see Chapter 5).

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‘False mice’ (Pseudomys Subgroup 1)

Plains mouse Pseudomys australis (~65 g) Shark Bay mouse Pseudomys fieldi (incl. P. praeconis) (~45 g) Long-tailed mouse Pseudomys higginsi (~65 g) Long-eared mouse Pseudomys auritus (EX)

Shark Bay mouse Plains mouse

Long-eared ? mouse Long-tailed mouse

This group contains some of the largest species of native mice, with the plains mouse and long-tailed mouse both being referred to as ‘rats’ in the past. The plains mouse was the first member of this group to be named and the close relationship of the plains mouse to the Shark Bay mouse and long-tailed mouse is not yet firmly established, but the latter two species are closely related. Some populations of animals referred to as plains mice have, in the past, been given separate specific names – for example those from the Nullarbor Plain, western New South Wales and southern Queensland. These populations seem to no longer exist (see Chapter 10) and two or more morphologically similar species appear to have become extinct in the recent past. The long-eared mouse is one such species. Now extinct, it used to occur on Kangaroo Island, along the shore of Lake Albert and in the south-east of South Australia, as well as in an adjacent region of western Victoria (see Chapter 10). The plains mouse is now probably restricted to a small region of gibber country to the south-west and west of Lake Eyre, where it typically lives in cracks of hard clay soil. The Shark Bay mouse in the recent past has only been found on Bernier Island in Shark Bay (arrow) of Western Australia. The long-tailed mouse is the only member of the Australian Old Endemics that is restricted to Tasmania where it lives mainly in wet and dry sclerophyll forests, alpine boulder fields and scree slopes. It occurred in the cold parts of the south-eastern mainland until only a few hundred years ago.

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‘Velvet mice’ (Pseudomys Subgroup 2)

Ash-grey mouse Pseudomys albocinereus (~30 g) Silky mouse Pseudomys apodemoides (~20 g) Smoky mouse Pseudomys fumeus (~50 g (east), ~70 g (west)) Blue-grey mouse Pseudomys glaucus (EX?) (?)

Ash-grey mouse Blue-grey mouse (EX?)

Silky mouse Smoky mouse

Members of this group are noted for their sleek, silky, grey fur, a fact reflected in the common names of most of the species. All of them have been recorded nesting or breeding communally (see Chapter 8). Silky mice occur in mallee and sandy heath regions of south-east South Australia and north-west Victoria where their activity is indicated by the presence of spoil heaps of sand left on the surface as a result of burrow construction. The smoky mouse is of serious conservation concern (see Chapter 10), while the blue-grey mouse is probably extinct, although there is some doubt as to whether it was in fact a separate species as it appears to be similar to the silky mouse. Two forms of the ash-grey mouse occur, one on Bernier Island (arrow) and the other, a larger-bodied form, on the mainland of Western Australia.

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‘Delicate mice’ (Pseudomys Subgroup 3)

Bolam’s mouse Pseudomys bolami (~15 g) Delicate mouse Pseudomys delicatulus (6–11 g) (incl. P. pilligaensis) Sandy inland mouse Pseudomys hermannsburgensis (~15 g) New Holland mouse Pseudomys novaehollandiae (16–25 g) North-western delicate mouse Pseudomys sp (undescribed)

Delicate mouse

North-western delicate mouse

Sandy inland mouse

Bolam’s mouse New Holland mouse

Most of the species in this group are very small. They are morpho logically similar to pebble-mound mice and short-tailed mice but have longer tails than the short-tailed mice and their foot morphology and behaviour separate them from pebble-mound mice. Despite their early discovery, their taxonomy and distributions are still not completely resolved. The sandy inland mouse is one of the most widespread of the Australian native rodents. It occurs in grassy areas and on sand dunes throughout much of the arid zone and often coexists with the spinifex hopping mouse. Bolam’s mouse is similar to the sandy inland mouse but generally has longer feet and tail. It occurs on chenopod plains, not sand dunes, in the southern arid zone. The delicate mouse is the smallest native rodent, generally not exceeding 10 g in weight, and it produces pups that weigh barely one gram at birth. Males of this species, as presently defined, have two very distinct sperm morphologies. This and other recently obtained data indicate that there are at least one, perhaps two, cryptic species within the delicate mouse, with one occurring in north-western Western Australia and one or two others in the Northern Territory and Queensland.

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Broad-toothed rat and chestnut mice (Pseudomys Subgroup 4)

Broad-toothed rat Mastacomys fuscus (~120 g) Eastern chestnut mouse Pseudomys gracilicaudatus (~70 g) Western chestnut mouse Pseudomys nanus (~55 g)

Western chestnut mouse Eastern chestnut mouse

Broad-toothed rat

The Broad-toothed rat has a darkly pigmented, short tail and a ‘rough’ appearance. It is found in cool climates of south-eastern Australia, in button grass plains of Tasmania and in alpine regions where it survives under snow in winter, thereby remaining active all year round. It is one of the most herbivorous of all Australian rodents and is thus ecologically and morphologically similar to the voles of the northern hemisphere. Associated with this is the occurrence of very broad molars and incisors (see Chapter 6). Its social organisation appears to change during the year from living a solitary existence in summer to a communal one in winter, presumably for warmth (see Chapter 8). The two species of chestnut mice are found in grasslands and heaths and have fairly wide distributions, although they are rare or extinct in many parts of their ranges. The western chestnut mouse occurs in northern Australia as well as on Barrow Island and islands in the Sir Edward Pellew group, but it is now probably extinct in the southern part of its range. It appears to have a unique reproductive biology for an Australian Old Endemic rodent species (see Chapter 5), and probably has a dispersed social organisation (see Chapter 8). The eastern chestnut mouse occurs patchily in coastal heathland from northern Queensland to northern New South Wales where, in the southern parts of its range, it competes with the swamp rat (see Chapter 7). Note: There is no definitive evidence that these three species form a taxonomically cohesive group. However, the generic name Mastacomys is probably invalid if the current usage of Pseudomys is continued as this species falls within the ‘pseudomys’ genus.

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Pebble-mound mice (Pseudomys Subgroup 5)

Kakadu pebble-mound mouse Pseudomys calabyi (~15 g) Western pebble-mound mouse Pseudomys chapmani (~12 g) Central pebble-mound mouse Pseudomys johnsoni (~12 g) (incl. P. laborifex) Eastern pebble-mound mouse Pseudomys patrius (~15 g)

Kakadu pebble- mound mouse Eastern pebble- Western pebble- mound mouse mound mouse Central pebble- mound mouse

Pebble-mound mice surround their nesting burrows with mounds of pebbles (see Chapter 8). They carry the pebbles in their mouths and shuffle them into position with their front feet when building the mounds. The known distributions of members of this group have been greatly expanded recently and it is now clear that pebbly hills across most of the tropics are occupied by pebble-mound mice. The Kakadu pebble-mound mouse occurs in Kakadu and Litchfield National Parks, the western pebble-mound mouse is patchily distributed in the Pilbara region, and the central pebble-mound mouse occurs from the Kimberley to the central Northern Territory and western Queensland. The eastern pebble-mound mouse was thought to be a form of the delicate mouse for almost 90 years from the time of its description in 1907. It was finally recognised to be a builder of pebble-mounds along the ranges of eastern Queensland where it was rediscovered in 1991 near Charters Towers. It has since been found in several other areas of eastern Queensland.

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‘Grizzled mice’ (Pseudomys Subgroup 6)

Desert mouse Pseudomys desertor (~30 g) Heath mouse Pseudomys shortridgei (~70 g)

Desert mouse

Heath mouse

The arid zone desert mouse and southern heath mouse appear, on genetic evidence, to be closely related, although their sperm morphology is markedly different (see Chapter 5). The heath mouse is one of the largest species of native mice and, unlike most closely related species, may form pair bonds during the breeding season (see Chapter 8). It is generally found on dry heaths or in stringy-bark forest with a heathy understorey. There are two populations, one in south-west Victoria and adjacent South Australia and the other in a small region of south-west Western Australia. The desert mouse occurs over much of the arid zone and also extends to the north dry savannah region of Queensland. It has large eyes surrounded by a ring of pale orange fur. It occurs in a range of habitats ranging from sand dunes with spinifex to rocky hillsides where it lives in shallow burrows.

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Other native mice (Pseudomys Subgroup 7)

Western mouse Pseudomys occidentalis (~35 g) Hastings River mouse Pseudomys oralis (~95 g) Gould’s mouse Pseudomys gouldii (~50 g (EX))

Gould’s mouse (EX)

Hastings Western River mouse mouse

The species in this subgroup are not closely related to each other. Their affinities to other native mice are uncertain although they are clearly members of the currently recognised genus Pseudomys. The western mouse has a uniformly dark grey pelage above and is grey-white below. It has large hind feet and may be deserving of separate generic distinction based on genetic, dental and skull characters. It is a communal species and occurs in about 10 isolated reserves in the wheat belt in south-west Western Australia. The Hastings River mouse is a rare species that is largely found in upland forest with some evidence of genetically distinct southern and northern forms. It was one of several native mice species rediscovered in the late 1960s. Gould’s mouse seems to closely resemble the Shark Bay mouse, and was collected from the Liverpool Plains of New South Wales and the Moore River region of Western Australia but has not been seen since 1856. Subfossil evidence suggests a wide distribution occurred across much of inland Australia.

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Rock-rats

Common rock-rat Zyzomys argurus (~35 g) Arnhem Land rock-rat Zyzomys maini (~100 g) Carpentarian rock-rat Zyzomys palatalis (~125 g) Central rock-rat Zyzomys pedunculatus (~100 g) Kimberley rock-rat Zyzomys woodwardi (~135 g)

Arnhem land rock-rat Kimberley rock-rat Common Common rock-rat rock-rat

Central rock-rat

Rock-rats are found in rocky habitats across northern Australia and in a small region of Central Australia. These species typically have a fattened tail base, which readily breaks off when held. Three large-bodied species have restricted distributions and are found in monsoon vine thickets associated with sandstone escarpments. The Kimberley rock-rat occurs in the north-west Kimberley region and on various islands off the Kimberley coast. The Carpentarian rock-rat occurs in five isolated rainforest patches in deep sandstone gorges or escarpments in the Gulf region. The Arnhem Land rock-rat is present in western Arnhem Land including Kakadu National Park where it lives among large sandstone boulders or on escarpments. The common rock-rat is much more widespread across the north and occurs in a greater range of rocky habitats than the larger-bodied species. The central rock-rat was believed to have become extinct around 1960 until the rediscovery of a very small population in the MacDonnell Ranges to the west of Alice Springs in 1996 (see Chapter 10).

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Melomys

Grassland melomys Melomys burtoni (~50 g) Fawn-footed melomys Melomys cervinipes (~80 g) ‘Grassland’ melomys (NG name) Melomys lutillus (~60 g) Cape York melomys Melomys capensis (~70 g) Bramble Cay melomys Melomys rubicola (~100 g)

NG Grassland Bramble Cay melomys melomys

Cape York melomys

Grassland melomys Fawn-footed melomys

Melomys are small rodents of wet northern habitats that have nearly hairless tails (see Chapter 4). The genus contains around 20 species that are found not only in Australia, but also in New Guinea and surrounding islands. Two of the five species found in Australia have restricted distributions on islands in the Torres Strait: the Bramble Cay melomys occurs on Bramble Cay and Melomys lutillus, which is widespread on the New Guinea mainland, occurs on the Australian-administered Dauan Island and may be the same species as the grassland melomys. The remaining species are relatively common in a limited area of mainland Australia. The fawn-footed melomys, which feeds on leaves and fruit (Chapter 6), is widespread in rainforests, some wetter schlerophyll forests and is occasionally found in mangroves along the east coast, whereas the Cape York melomys occurs in rainforests of northern Cape York. The grassland melomys is generally found in grassy areas, but can also occur in monsoon thickets, swamps and riparian woodlands as well as in canefields of north Queensland where it can become a pest. Coat colour and body size vary considerably between different populations – future taxonomic studies are likely to demonstrate at least one further species.

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White-tailed rats

Giant white-tailed rat Uromys caudimaculatus (~650 g) Masked white-tailed rat Uromys hadrourus (~200 g)

Giant white- tailed rat

Masked white- tailed rat

The giant white-tailed rat is one of Australia’s largest rodents. It has a reputation among residents of northern rainforests as a coconut-eating, tin-can opening, beast that invades houses and camp sites. It climbs well using its hind limbs to propel itself forwards like a tree-kangaroo and lives in holes in trees or under logs on the ground. There are two chromosome races, one ranging from Cooktown to Townsville and the other occurring in the northern parts of Cape York. The masked or pygmy white-tailed rat was discovered in 1973 on the summit of Thornton Peak. Since then populations have been found on Thornton Massif, the Mount Carbine Tableland and Atherton Tablelands. Both species spend time in the rainforest canopy as well as on the forest floor. The giant white-tailed rat also inhabits more open forest and woodland adjacent to rainforests.

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Water rat

Water rat Hydromys chrysogaster (~700 g)

Water rat Water rat

The water rat is one of the largest Australian rodents and is adapted for a carnivorous aquatic lifestyle and hence appears superficially somewhat like an otter or mink. The main morphological adaptations include thick water-repellent fur, a somewhat flattened head with broad muzzle, small ears and eyes, long whiskers, short limbs, partly webbed hind feet and a long, muscular, white-tipped tail. In many of these adaptations the water rat shows convergence to fish-eating rodents of South America. The water rat has distinctive ‘basin-shaped’ molars for eating a variety of invertebrate, and even occasional vertebrate prey (see Chapter 6). It lives equally well in fresh or salt water and, unusually for a native rodent, is partly diurnal. Some individuals have a beautiful golden belly fur which, it has recently been suggested, may associate with greater aggressiveness and hence territorial activity.

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Water mouse

Water mouse Xeromys myoides (~40 g)

Water mouse

The northern Australian and southern New Guinean water mouse is much smaller than the water rat to which it is only quite distantly related, being closer to several species in New Guinea. It has a sleek coat which is slate- grey above and white below, with its tail lacking a white tip. Like the water rat, it has only two, not three, molars in each row. It lives in mangrove swamps where it preys on invertebrates, such as crabs, in the tidal zone (see Chapter 6) and is sparsely distributed along the coasts of Queensland and Northern Territory. Its activity is greatly influenced by the tidal cycle and it emerges to forage amongst mangroves as the tide ebbs.

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Prehensile-tailed rat

Prehensile-tailed rat (or tree mouse) Pogonomys (mollipilosus?) (~65 g)

The prehensile-tailed rat is a rainforest specialist characterised by having a prehensile tail. It has pink feet, a dark-ring around the eye, white belly fur and soft grey upper body fur. It was first recorded in 1974 from the Atherton Tablelands with a number of individuals having recently been found in two small areas of north-east Queensland including near Cape Tribulation. The specific identity of this species and its relationships to New Guinean members of the genus are not known. Also, little is known about its biology due to the difficulty of trapping it, but its remains have been found to be relatively abundant in owl pellets, suggesting that it may be relatively common in tropical rainforests.

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Native Rattus or true rats

Dusky rat Rattus colletti (~70 g) Bush rat Rattus fuscipes (~100 g) Cape York rat Rattus leucopus (~130 g) Swamp rat Rattus lutreolus (~100 g) Canefield rat Rattus sordidus (~150 g) Undescribed species Rattus sp. (~120 g) Pale field rat Rattus tunneyi (~130 g) Long-haired rat Rattus villosissimus (~150 g)

Dusky rat

CR Canefield rat Cape York rat

Swamp rat Bush rat Long-haired rat Rattus sp. Pale field rat

t a r h s u Bush rat B Swamp rat

Native Rattus species occur naturally in most regions of Australia and are distinguished from Old Endemics by their rough tails with coarser hair than the Old Endemics, overlapping scales on the tail and stiffer body hairs. Also, unlike the Old Endemics, females have one to three pairs of pectoral nipples (see Chapter 5). In the Wet Tropics of north-eastern Australia, five species are present in a relatively small area, but in most regions only one or two species occur in any given habitat. The taxonomy of the Australian Rattus species is still under review with at least one species awaiting formal description. The relationships between Australian

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true rats and the other species in this genus outside Australia are not fully known. The following is a brief outline of the currently described species in Australia. The bush rat occurs as four subspecies and ranges from south-west Western Australia to northern Queensland. It is one of the most common species of small native mammals, and is widespread in both eucalypt forests and rainforests especially where there is dense understorey of shrubs and ferns in deep gullies. The swamp rat, which is a much darker animal than the bush rat, inhabits swampy areas of south-east Australia with a separate subspecies occurring in Tasmania where it occupies a broader range of habitats and is referred to as the velvet-furred rat with another subspecies occuring in north-east Queensland. The long-haired rat periodically appears in very large numbers in the drier parts of northern, eastern and central Australia after sustained periods of good rains. The canefield rat occurs in diverse habitats of grassland and open forest. It is a colonial species and one of the very few species of native rodent that can become a pest due to its periodic high numbers in cane fields of northern Queensland. The dusky rat occurs on sub-coastal alluvial flood plains of the Northern Territory and, during the wet season, it retreats to higher ground of levee banks and margins of the flood plains. The pale field rat appears to be dependent upon riparian vegetation for its existence. It used to be quite extensively distributed but is now rare or absent from the arid region (see Chapter 10). The Cape York rat is present as two chromosomally different subspecies. One is present on Cape York and the other from Cooktown to the Townsville area where it lives sympatrically with the northern subspecies of the bush rat. In addition to the species occurring on the Australian mainland, two extinct forms – Maclear’s rat (R. macleari) and the bulldog rat (R. nativitatus) – once lived on the Australian territory of Christmas Island, but both species became extinct shortly after 1900, probably due to the introduction of a trypanosome parasite in the black rat (see Chapter 9).

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Introduced species

House mouse Mus musculus domesticus (~20 g) Pacific rat Rattus exulans (~50 g) Black rat Rattus rattus (~260 g) Brown rat Rattus norvegicus (~300 g)

Pacific rat

Black rat Black rat

House mouse

Brown rat Brown rat

These species were inadvertently introduced into Australia during the early days of European settlement. The house mouse is the most widespread, non-human, terrestrial mammal in the world and occurs throughout most of the continent. It occurs in human dwellings as well as in cultivated fields and throughout much of the arid zone where plagues sometimes occur. It can be distinguished from the native rodents by its musty smell and small eyes. It also occurs in natural vegetation and can become extremely abundant after fire. The introduced rats occupy disturbed areas. The brown (Norway) rat is largely restricted to cities and towns and is rarely found far from human habitation. The black (roof) rat is more widespread and occurs in agricultural areas, in cities and towns as well as along banks of rivers and creeks and the seashore. It can also sometimes be found in bushland environments and wet forests but does not appear to have displaced any native rodent species. The Pacific rat has only been recorded on offshore islands, such as Adele Island off the Kimberley coast. It also occurs on Norfolk Island where it was probably introduced by the Polynesians. Unlike in New Zealand, the Pacific rat does not appear to have become established on the mainland.

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lthough many of the Australian native rodents were once more Awidespread than they are today, one or more species are still found throughout most of the Australian landmass. In parts of inland New South Wales, the only native rodent species that occurs is the water rat. By contrast, in the near-coastal areas of the Top End of the Northern Territory, the Kimberley and north-east Queensland, a number of species can commonly be found in close proximity to each other. The greatest diversity occurs in north-east Queensland where up to 17 species of mice and rats are present. The Top End of Australia and the Kimberley region also have high species richness (13 species) as does the coast and hinterland of the New South Wales–Queensland border (10–11 species). The Pilbara coast, Barrow Island and Shark Bay in north-west Western Australia have seven to nine species, and the vicinity of Lake Eyre has around seven species. Fewer than five species are found in most areas of southern Australia. The pattern of the present rodent distributions in Australia is partly a reflection of the fact that each major group has its own broad ecological preferences. For example, the Australian Old Endemics, such as the native

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>12 species 9–12 species 6–9 species 3–6 species <3 species

Figure 3.1 Number of native rodent species found at the present time within each of 203 grid cells (measuring 2.5 degrees of latitude x 2.5 degrees of longitude) across Australia.

mice in the genus Pseudomys and hopping mice, generally occur in dry habitats, while the mosaic-tailed rats and, to a lesser extent the native Rattus, are mostly found in the wetter, more coastal, regions. Thus, in regions such as north-east Queensland where all these habitat types occur in a small area, the di vers ity of species is very high. The pattern of species diversity has nevertheless been greatly affected by recent extinctions. This has reduced the number of species across most of southern Australia and has resulted in only a few species remaining in areas such as inland New South Wales.

Regional faunas Studies of the distributions of Australian animals including birds, reptiles and marsupials have identified three major zones that generally have similar groups of species found at different locations within them, but which have different groups of species compared to locations in the other zones. These are the Bassian (eucalypt forests and woodlands of southern Australia), Eyrean (arid and semi-arid zones) and Torresian (northern tropical forests, woodlands and savannahs) zones. Generally,

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rodent faunas within each of these zones are similar to each other, but differ markedly from those of the other two zones. However, there are seven smaller regions within these larger zones that more fully account for the distribution of rodent faunas around the continent. These regions are:

• northern savannah • arid zone • north-east wet forests • north-east dry forests • Pilbara • south-west • south-east These regions are loosely based around clusters of similar habitats, and are often demarcated by geographical boundaries such as deserts.

NE Wet Forests Cape York Nth SavannahsTop End

Kimberley NE Dry Forests Wet Tropics Pilbara Eungella

Arid Zone Shark Lake Eyre Bay Basin SW Forests Southern arid zone

Heaths

SE Forests

TAS

Figure 3.2 Major regions of Australia in which distinct assemblages of rodent species occur.

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The boundaries are not always sharp and can change even between seasons. Each of these regions contains at least one endemic species as well as a unique combination of species. Widespread species such as the water rat and bush rat are found in more than one region. Obviously not all rodent species occurring in a region will be present at every location. In fact, most species are generally not present at most locations where they were originally found. Communities containing multiple species of rodents still occur at favourable sites and are relatively common in northern Australia, but are rare in the south. This was not always the case. Owl pellet deposits indicate that many species of mice and rats in south-eastern Australia occurred in proximity to each other 200 years ago, with structured rodent communities probably being common in southern forests before European influence. The northern savannahs have the richest rodent communities, although there is now a growing fear that a decline in distribution and abundance may be taking place in some of the species in these regions. These communities contain large (up to 800 g) and medium-sized scansorial rats (tree rats and rabbit rats), together with native Rattus and small, medium and large native mice and short-tailed mice. Often, many of these species can be found in the same general location and, if there is a watercourse nearby, the water rat may also be found. In addition, rock-rats (which occur in rocky outcrops) may also forage in nearby habitats and can be found in association with any of the above genera, for example at Nourlangie Rock in Kakadu National Park. Although fewer species are present in the north-east wet forests, many locations within that region have relatively rich rodent communities due to consistent high productivity. For example, at many sites in the Wet Tropics, one can encounter one or two species of native Rattus, a melomys, the giant white-tailed rat and the prehensile-tailed rat. Sometimes there may also be water rats and common rock-rats present. Communities in the arid zone are far more fluid in their composition and have been markedly depleted by recent extinctions. What a natural arid zone rodent community would have been like a few hundred years ago is not known owing to the extinctions that have occurred since that time. However, at many sites a mixture of up to five species of small, medium and large-bodied native mice, as well as hopping mice and one or two stick-nest rat species, are likely to have been present.

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In the forests of southern Australia, multiple species of mice and rats may have once coexisted. Today there are few sites where more than one native Rattus and a native mouse species occur together. Up to six species of native mice and a native Rattus species may be found at the more productive sites in the north-east dry forests, but generally fewer species than this are encountered. Tables 3.1 to 3.7 show the total number of species for each region. All species recorded within a region are indicated, whether or not they are now present. Endemic species are shown in italics, ‘(EX)’ indicates a globally extinct species, and ‘(ex)’ indicates regional extinction. Distributions are the primary area of occurrence within the region. ‘Other species’ listed after the main table are typical of other regions, but have limited, or occasional occurrences, within the region.

Northern savannah This region has strongly seasonal summer rainfall and is dominated by open eucalypt woodlands or forest with a grassy understorey (generically termed ‘savannahs’). There are also pockets of monsoonal rainforest, dry hummock grasslands, mangroves, swamps and numerous escarpments. The region contains two important sub-regions – the North Kimberley and the Top End – that incorporate two similar, but isolated, productive pockets of wetter habitats on sandstone. These correspond to the areas of high species diversity shown in Figure 3.1., and contain very similar species assemblages. Populations of birds, reptiles and mammals from the two areas are generally regarded as subspecies of the same species, or recently diverged sibling species. Among native mice and rats, such relationships are seen in the presence of species such as the brush-tailed rabbit rat in both these regions and the sib-species relationship between the Kimberley and Arnhem Land rock-rats. The diversity of habitats in this region means that it contains the greatest taxonomic and ecological diversity of any rodent fauna in Australia. Twenty species here are widespread or endemic, and other species are occasionally present in parts of the region (Table 3.1). The region contains representatives of all major Australo-Papuan Old Endemic lineages except the prehensile-tailed rat, as well as native Rattus. Endemic components of the fauna are three species of large rock-rat: the Arnhem Land rock-rat, the Kimberley rock-rat and the Carpentarian rock-rat

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Table 3.1. Native mice and rat species of the northern savannah. Species Distribution Habitats Brush-tailed rabbit rat North Kimberley & Top Eucalypt woodland End, New Guinea Water rat Widespread Waterways Tropical short-tailed Widespread Grassland/woodland mouse Grassland melomys Close to coast Vine thicket/swamp Black-footed tree rat Widespread Eucalypt woodland Golden-backed tree rat North Kimberley & Top Woodlands/vine thickets End Northern hopping North-east of Top End Sand dunes mouse Kakadu pebble-mound Top End Grassy eucalypt mouse woodland Delicate mouse Widespread* Grasslands/woodland ‘Delicate mouse’ Southern Kimberley* Spinifex grasslands Central pebble-mound North Kimberley Grasslands/woodland mouse Western chestnut mouse Widespread Grasslands/woodland Dusky rat Top End Wetlands/crops Pale field rat Widespread Grasslands/woodland Long-haired rat Southern margins of Crops/various when Ord basin present Water mouse Coastline of the Top End Mangroves Common rock-rat Widespread Rock outcrop any vegetation Arnhem Land rock-rat Top End, endemic Vine thicket/escarpment Carpentarian rock-rat Far east of region Vine thicket/escarpment Kimberley rock-rat North Kimberley Vine thicket/escarpment Other species: Canefield rat (recorded from Pellew Islands), desert mouse (southern margins of entire region), sandy inland mouse (southern margins of entire region), desert short-tailed mouse (southern margins of central and eastern parts of the region). *Taxonomy in review – multiple taxa have been described as the delicate mouse, at least two of which are probably distinct species Endemic species are given in italics

(which is known from just five sites near the eastern margin of the region), as well as the Kakadu pebble-mound mouse, the brush-tailed rabbit rat and the dusky rat. High diversity is primarily associated with eucalypt woodland habitats, which tend to have an understorey of tussock and sod grasses. The ‘tall grass savannahs’ of Kakadu, dominated by Sorghum spp., are a

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good example. More open eucalypt vegetation in the south of the region has a spinifex understorey. Such habitats retain a relatively diverse small rodent fauna, but tend to lack larger-bodied species and intergrade with the arid zone faunas to the south. Areas dominated by lancewood (Acacia shirleyi) generally provide poor habitat for rodents.

Arid zone Arid Australia (including the semi-arid margins of the true deserts) is typified by sandy deserts and clay plains interrupted by rugged rocky ranges. The arid zone and the Pilbara are the only regions in which vegetation is not dominated by eucalypt communities. Acacia, spinifex hummock grasses and chenopod shrubs, such as saltbush, dominate arid habitats. Where eucalypts occur, they are often very sparse, scattered, or restricted to waterways and hillsides. Rainfall in the arid zone is unpredictable, although the northern deserts receive higher and more regular rainfall due to a weak effect from summer monsoonal rains. There are no permanent waterways through most of the region and the lakes are ephemeral salt pans. Despite the harshness of the arid zone, it once had a rich rodent fauna like deserts of other continents. For instance, the southern part of the arid zone has, or had, several distinct resident species such as Mitchell’s hopping mouse, Bolam’s mouse and the stick-nest rats, whereas the region around Lake Eyre contains three hopping mouse species. The boundaries of these areas are difficult to define, and the natural distribution patterns of the resident species are not well known. Dryness has favoured lineages of small and medium-sized mice in the Australian Old Endemic grouping. No mosaic-tailed rats occur, but the limited waterways of the east have water rat populations and, in moister refuge areas, two species of native Rattus have been recorded. The hopping mice are a distinctive component of the arid zone fauna and in some ways show convergence to the desert rodents, such as jerboas and kangaroo rats, occurring on other continents (Chapter 4). At least six species were endemic to this region. Four still survive: the spinifex hopping mouse, Mitchell’s hopping mouse, the dusky hopping mouse and fawn hopping mouse. Two species of stick-nest rat were the largest arid zone rodent species and were once widespread across the southern half of the zone but both are now extinct on the mainland. Most of this country’s recent rodent (and marsupial)

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Table 3.2. Native mice and rats of the arid zone. Species Distribution Habitats Water rat Eastern margins, also New Waterways Guinea Desert short-tailed Central and north-east Various mouse Tropical short-tailed Northern deserts Various mouse Lesser stick-nest rat (EX) Southern ? Greater stick-nest rat Southern, Franklin Is Spinifex hopping mouse Widespread Spinifex/sand plains Fawn hopping mouse Lake Eyre basin Gibber/clay plains Dusky hopping mouse Lake Eyre Basin, central SA Spinifex/sand plains Long-tailed hopping Widespread ? mouse (EX) Mitchell’s hopping Southern third of region Mallee/sand plains mouse ‘Broad-cheeked hopping Flinders Ranges ? mouse’ (EX) Plains mouse Lake Eyre basin Naturally various Bolam’s mouse Southern third of region Sand plains ‘Delicate mouse’ Great Sandy Desert Spinifex/sand plains Desert mouse Widespread Various Shark bay mouse (ex) Widespread ? Gould’s mouse (EX) Southern Grassland/sand plain Sandy inland mouse Widespread Various Central pebble-mound Central northern deserts Rocky ridgelines mouse Western mouse (ex) Southern coast ? Pale field rat (ex) Widespread? ? Long-haired rat1 North and north-east Drainages, various1 Common rock-rat North Rocky ranges Central rock-rat Central and north-west (ex) Rocky ranges Other species: Delicate mouse (north and Queensland form in north-east), western chestnut mouse (north), eastern chestnut mouse (north-east – e.g. ‘Desert Uplands’ of Queensland), bush rat (islands off South Australian coast). 1When in plague

extinctions have occurred in the arid and semi-arid zones and, among rodent species that exceed 60 g in body weight, only the plains mouse and central rock-rat have survived. Both are now rare and/or very restricted in their distribu tions. The smaller species have survived better; those that remain generally have large distributions and inhabit a wide range of habitats.

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Native mice and rats of the arid zone are often quite general in their use of vegetation communities. Grasslands of the north-east tend to contain few rodents when compared to spinifex habitats of the northern deserts, and stick-nest rats may once have preferred chenopod shrublands of the south. As in other parts of the continent, dense stands of wattle are not favoured by rodents, but open wattle/spinifex communities are a common habitat frequented by several species.

North-east wet forests The forests of the north-east receive high year-round rainfall. Because of high levels of evaporation under the tropical sun, rainforests are restricted to the mountain ranges and adjacent lowlands that promote formation of cloud, increased rainfall and reduced temperatures and evaporation. They therefore occur only in isolated blocks along the Queensland coast and are often associated with a narrow band of wet eucalypt forest in which ‘rainforest’ species like the giant white-tailed rat, native Rattus and melomys all are present. Rainforests and wet eucalypt forests of this region contain perhaps the least typical of all Australian rodent faunas. New Guinean groups Table 3.3. Native mice and rats of the North-east Wet Forests. Species Distribution Habitats Water rat Widespread, also New Waterways Guinea (NG) Grassland melomys Widespread Eucalypt forests Fawn-footed melomys Widespread Rainforests, margins Cape York melomys Cape York Peninsula Rainforest margins Prehensile-tailed rat Cape York Peninsula, Rainforests Wet Tropics, also NG* Bush rat Cape York Peninsula, High-altitude rainforests Eungella Cape York rat Cape York Peninsula, Rainforests, margins Wet Tropics, also NG Swamp rat Wet Tropics, Eungella Grassy forest Giant white-tailed rat Widespread, also NG Rainforests, eucalypt forests Masked white-tailed rat Wet Tropics Rainforests Other species: Common rock-rat (occasionally encountered, notably at Black Mountain near Cooktown), pale field rat (eucalypt forests at margins of region), canefield rat. *Depending on taxonomic identity of the Australian species

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dominate the fauna and Australian Old Endemics are absent, except for occasional intrusions by common rock-rats. Native Rattus are common, with three species occurring, including isolated endemic sub-species of the bush rat and the swamp rat. The region can be further sub-divided into Cape York Peninsula, the Wet Tropics and Eungella. The fauna of Cape York is adapted to hot climates and lowland rainforests. Species such as the Cape York rat and Cape York melomys as well as generalists such as the giant white-tailed rat occur in the northern region, whereas Eungella contains only a few species with primarily southern, cooler, affinities such as the bush rat and swamp rat, and also melomys species with broader distributions to the north and south. The Wet Tropics contain the highest species diversity by virtue of the fact that altitudinal and climatic variation of the region permits the overlap of the Cape York and Eungella faunas.

North-east dry forests The north-east dry forests are dominated by dry eucalypt savannah and forest habitats similar to the northern savannah region, but the two regions are isolated by dry habitats south of the Gulf of Carpentaria. The southern limit of the region corresponds to the interchange between summer dominated rainfall and the largely winter rainfall of the south-east. This also roughly corresponds to a change in under storey dominance in forests from grasses in the north-east to more shrubby habitats in the south-east. The brigalow belt, an area naturally dominated by Acacia harpophylla and associated communities, forms a band through the central and southern parts of the region. Much of this area has been cleared for agriculture, but ranges of the brigalow belt have significant populations of rodents such as the eastern pebble-mound mouse, and isolated vine thickets harbour fawn-footed melomys. Given the similarity of eucalypt-dominated habitats between this region and the northern savannah region, there are some notable absences from the north-east. For instance there are no records of large rock-rats, although recent fossils of large rock-rats have been found at Chillagoe at the base of Cape York. The brush-tailed rabbit rat has also not been recorded, although it occurs in the Top End, as well as in the south of New Guinea and on Mornington Island in the Gulf of Carpentaria. Targeted

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Table 3.4. Native mice and rats of the North-east Dry Forests. Species Distribution Habitats Water rat Widespread Waterways Tropical short-tailed North Various mouse Grassland melomys East Eucalypt forest/woodland Black-footed tree rat North Eucalypt woodland Darling Downs hopping Far south ? mouse (EX) ‘Delicate mouse’/Pilliga Widespread, also NG?1 Various mouse Desert mouse Central, south Various Eastern chestnut mouse East Heath and woodland Eastern pebble-mound Central, south Woodland on rocky mouse ridges Giant white-tailed rat North Drainages/wet pockets Canefield rat Near-coastal Woodland/forest, crops Pale field rat Widespread Woodland/open forest Undescribed rat Emerald district Grassland/woodland Common rock-rat Central, north Rocky outcrops Water mouse Southern coasts Mangroves Other species: Fawn-footed melomys (vine thickets, wetter forest margins), Cape York rat (drainage lines and closed forest pockets on Cape York), sandy inland mouse (western margins), plains mouse (ex) (far south), long-haired rat (western margins), blue-grey mouse (EX) (far south?), swamp rat (south-east), bush rat (south-east) 1Depending on taxonomic identity of New Guinean taxon Endemic species are given in italics

surveys of suit able habitats on Cape York may yet reveal the presence of these species. There are only two described species endemic to this region, the eastern pebble-mound mouse and Darling Downs hopping mouse, although the delicate mouse of this region may be described as a separate species in the near future. There is also an undescribed endemic species of native Rattus. Rodents are most abundant in the eucalypt woodlands and savannahs adjacent to the north-east wet forests. Wattle-dominated vegetation is generally poor in rodents. Large areas of Melaleuca-dominated vegetation on Cape York may be good habitat for rodents where there is a well- developed grassy understorey, but have been poorly surveyed. Rodents probably avoid the seasonally inundated Melaleuca thickets.

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The Pilbara The Pilbara is dominated by rocky ranges that rise above the sand dunes of the Great and Little Sandy Deserts to the east. Acacia and spinifex dom inate the vegetation, although scattered eucalypts occur as well. The rocky substrates of the Pilbara region are not suitable for some typical arid zone species such as hopping mice, and several species found in the region have closer ties with the northern savannahs than they do with the rest of the arid zone, which is due to older savannah habitats being slowly replaced by desert over the last 500 000 years or so. The region therefore contains a unique blend of arid and savannah species. Sparsely vegetated rocky ridges provide ideal habitat for the only endemic rodent species of the region, the western pebble-mound mouse. A golden-backed tree rat was captured near the Pilbara coast in the 1800s but this species has not been seen in this region since that time. Sub-fossils of the arid zone central rock-rat, which has not been recorded live in the region, have also been found. Spinifex is by far the most abundant component of Pilbara vegetation, and nearly all rodents in the region have been recorded from sites where spinifex occurs. Gorges and ranges with richer vegetation mosaics may have been important to the golden-backed tree rat and central rock-rat.

Table 3.5. Native mice and rats of the Pilbara. Species Distribution Habitats Tropical short-tailed mouse North, Thevenard Is. Various Golden-backed tree rat (ex) North ? Western chestnut mouse Barrow Is, North (ex) Spinifex Desert mouse (ex?) Widespread? Various ‘Delicate mouse’ North Various Sandy inland mouse Widespread Various Western pebble-mound Widespread Rocky ridges mouse Pale field rat North coast Grassland/spinifex Common rock-rat North and west Rocky ranges Central rock-rat (ex) Cape Range, ? widespread? Other species: Spinifex hopping mouse (sand dunes around margins and between the Cape Range and Pilbara), water rat (north coast and Barrow Island).

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South-west South-western Western Australia is renowned for its unique endemic flora. Although eucalypts dominate the vegetation of this region, forests are restricted to the far south-west. Much of the remainder of uncleared land is open woodlands or heaths, with banksias being a significant feature of the flora. Sandy soils underlie most of the area. The climate is one of hot summers and cool winters. Rainfall occurs predominantly in the winter, but only the far south-west commonly receives significant rain. The dryness of the region is emphasised by its faunistic association with the arid zone – four species of hopping mice species used to occur here. However, the region also has close ties with the south-east, in particular

Table 3.6. Native mice and rats of the South-west. Species Distribution Habitats Water rat South-west and Shark Watercourses, islands Bay Lesser stick-nest rat (EX) Semi-arid belt ? Greater stick-nest rat (RI) ? Long-tailed hopping Moore River, ? ? mouse (EX) Big-eared hopping mouse Moore River, ? ? (EX) Mitchell’s hopping Southern semi-arid belt Mallee/sand plain mouse Ash-grey mouse Semi-arid belt Various Gould’s mouse (EX) Moore River, ? Grassland/sand plain Western chestnut mouse Moore River, ? ? (ex) Western mouse South-east, west coast Various (ex) Shark bay mouse Shark Bay Dunes and spinifex Heath mouse South-east, west coast Shrubby open eucalypt (ex) Bush rat South and central coasts Forests and wet shrublands Pale field rat Shark Bay, west coast ? (ex) Other species: Bolam’s mouse (south-eastern margin), desert mouse (northern semi-arid belt and inland margins), spinifex hopping mouse (northern semi-arid belt and inland margins), sandy inland mouse (northern semi-arid belt and inland margins). Endemic species are given in italics RI = reintroduced

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the sandy, dryland heaths and woodlands of western Victoria and south- eastern South Australia. Heath-dwelling species, and those shared with arid zones, are generally absent from the far south-west, but occupy a band of semi-arid habitat stretching from around Shark Bay in the north-west to near Esperance in the south-east. There used to be two endemic species in the south-west, the ash-grey mouse and the big-eared hopping mouse. However, like several marsupial species, extant populations of previously more widespread species, the western mouse and Shark Bay mouse, are now known only from this region. The semi-arid belt of banksias, heaths and open eucalypt communities contains the bulk of species with the northern region around Shark Bay being a refuge for several rodent, as well as marsupial, species. Forests contain few rodent species with several species in the far south-west having become extinct.

South-east This region has the greatest altitudinal variation on the continent and significant snowfalls occur here in places. Rainfall varies from uniform in the north to winter-dominated in the south. Winters are generally cool in the south and mild in the north, with summers being hot in the north, but cooler in the south. The south-east contains the most extensive eucalypt forests in Australia, and patches of warm and cool temperate rainforest occur in the coastal hinterland. The transition between wetter coastal forests and dry inland plains and woodlands is more gradual in the south- east compared to other parts of the continent. Some ‘arid zone’ species (e.g. plains mouse and Gould’s mouse) were first discovered within this region. The blue-grey mouse may once have had a distribution spanning the inland transition from forest to the arid zone habitats. There have been marked range reductions among native mice that dominate rodent faunas of this region. Of the Australian Old Endemics, the white-footed rabbit rat used to occur here but became extinct shortly after the arrival of Europeans. The dryland heaths of the east sub-region (western Victoria and south-eastern South Australia) contain species closely related to those in the south-west region, but also some species, such as swamp rats, that are typical of the rest of the region.

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Table 3.7. Native mice and rats of the South-east. Species Distribution Habitats Water rat Widespread Waterways White-footed rabbit rat Widespread Eucalypt woodlands (EX) Broad-toothed rat South-east highlands Moist and cool forests heath/forest/grassland Grassland melomys North-east Heath/Forest Fawn-footed melomys North-east Moist forests Mitchell’s hopping West Mallee/sandplain mouse Silky mouse West Heath/mallee/sandplain Plains mouse (ex) Liverpool plains, ? ? Smoky mouse South-east mainland Heath/heathy forest Gould’s mouse (EX) Liverpool plains, ? Grassland/sandy plain? Eastern chestnut mouse Central and northern Heath/heathy forest coast Long-tailed mouse Tasmania, Snowy Various wet and dry mountains? (ex) forest New Holland mouse Widespread Heath/forest Hastings River mouse North-east ranges Various forest Heath mouse West and nearby areas Heath ‘Basalt Plains mouse’ (EX) Basalt Plains, southern ? Victoria Bush rat Widespread Various forest Swamp rat Widespread, Tasmania Heath/swamp/grassland Other species: Lesser stick-nest rat (EX) (Murray-Darling junction), greater stick- nest rat (ex) (Murray-Darling junction), Bolam’s mouse (ex?) (recent records near Mildura), desert mouse (ex) (Murray-Darling junction), ‘delicate mouse’/Pilliga mouse (inland north-east), pale field rat (north-east).

Tasmania contains a diverse range of habitats from temperate coasts to a maritime alpine zone. Extensive beech (Nothofagus) rainforests are found alongside glacier-scarred alpine plateaus and drier eucalypt forest in the east. It has the distinction of being the site from which the first Australian rodent was described; the water rat. The long-tailed mouse is now endemic to Tasmania, but it survived in colder areas of the mainland until at least a few hundred years ago and was probably extant when Europeans colonised the south-east mainland. Surprisingly, the bush rat, so ubiquitous in mainland forests, is not found in Tasmania where an endemic subspecies of swamp rat is the sole native Rattus species.

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Rarely now do more than two rodent species co-occur in forests. Coastal and inland heaths have high densities of rodents, but cover only small areas, except in the west of the region where they are widespread under a scattered eucalypt cover, often with stands of mallee, although the undescribed ‘Basalt Plains mouse’ may have exploited grasslands in south-western Victoria.

The bush rat, common in mainland forests, is surprisingly not found in Tasmania. Drawing by Ella Fry.

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lthough rodents have been on the Australian continent for a relatively Ashort period of time compared to marsupials, they have diversified into a wide array of body forms and ways of life. This diversity is the result of three major processes; invasion, adaptation and speciation. Rodents are among a number of plant and animal groups that have invaded Australia from the north over the last 20 million years. These invaders joined an older, resident biota that was inherited from the supercontinent of Gondwana, including two other groups of terrestrial mammals, the monotremes and marsupials. Invasion of Australia probably commenced soon after it broke away from Antarctica around 50 million years ago, but became more frequent as it drifted increasingly close to Asia, reducing a previously wide ocean barrier into a series of smaller inter-island crossings. Although many elements of the modern Australian flora and fauna are derived from Asia, rodents are the only terrestrial mammals that have achieved this crossing without the assistance of humans.

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Fossil history Establishing exactly when rodents arrived in Australia requires a good fossil record. Unfortunately environmental conditions in Australia during the Tertiary period (65 to 1.8 million years ago) were generally poor for preserving fossils, hence there are very few deposits known to contain faunas from this time period. There are several significant deposits with rodent fossils (Table 4.1) and these show that rodents arrived no later than 4 million years ago. A few deposits that contain rodent fossils may be older than this but they are not dated accurately enough to be certain of their age. One site at Hamilton in Victoria dated to the early Pliocene, around 4.5 million years ago, contains teeth of rodent-sized marsupials but no rodents. The absence of rodents from this deposit has been suggested as indicating that they had not reached southern Australia by this time. The site of Rackham’s Roost at Riversleigh in western Queensland contains abundant rodent fossils belonging to three modern rodent genera, all members of the Australian Old Endemic Group, as well as some extinct forms (Table 4.1). Rackhams’s Roost may date to around the same period as the Hamilton deposit but its age has yet to be firmly established. By the end of the Pliocene period, around 2 to 2.5 million years ago, diverse rodent faunas were established in southern Australia. The best evidence comes from Fisherman’s Cliff on the lower Murray (Table 4.1). This site contains species closely resembling modern species of stick-nest rat, native mice of the genus Pseudomys, and hopping mice. So far, the only evidence of a rodent group other than the Australian Old Endemics in a mid- to late Pliocene deposit is a tooth from a species of water rat found on Barrow Island (Table 4.1 and Fig. 4.2). The lack of evidence of any other groups of rodents in the Pliocene deposits is intriguing, but whether this is because they failed to reach Australian shores during this period, or arrived but failed to become widely established, cannot be determined. However, the genus Rattus is so widely distributed today that its absence in all Pliocene deposits surely points to a more recent arrival. On the whole, the fossil record seems to indicate that the ancestors of the Australian Old Endemic Group first arrived in Australia sometime very late in the Miocene (<6.5 Mya), when low sea levels may have aided them to do so, or during the early Pliocene (around 5 Mya). Later arrivals included water rats, mosaic-tailed rats, and native Rattus with one or more species of Rattus arriving during the Pleistocene.

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Table 4.1. Pliocene fossil mice and rats of Australia. Site Location Age Rodents present Parwan Southern Victoria 4.06–4.2 Mya Rodent Bluff Downs North-east 3–4 Mya Rodent (1 sp.) Queensland Kanunka North-east South 3.4 Mya Native mouse Australia Riversleigh North-west 3+ Mya Short-tailed mice (2 spp.) Queensland Native mice (7 spp.) Rock-rat (1 sp.) Barrow North-west 2.8–3.6 Mya Native mouse (1 sp.) Island Western Australia Rock-rat “Water rat” Chinchilla South-east 2–3 Mya Native mouse (Ex. species) Queensland Fisherman’s North-west 2.42–2.87 Mya Undescribed genus1 Cliff Victoria Short-tailed mouse Lesser stick-nest rat Hopping mouse (1 sp.) Native mice (2 spp.) Silky mouse Western mouse Dog Rocks Southern Victoria 2.03–2.48 Mya Native mice (2 spp.) Floraville North-west ~2 Mya (?) Native mice spp. Queensland Native Rattus Malkuni North-east South ~2 Mya Rodent Australia 1 Probably a native mouse Mya = millions of years ago

Numerous deposits of late Pleistocene age (<150 000 years ago) have produced abundant rodent fossils (Table 4.2) nearly all of which are of modern species. Most sites are in caves located below owl roosts but there are also lake and river deposits of this age in central Australia. Changes in species composition recorded in south-eastern Australian deposits show marked changes related to climatic warming since the end of the last glacial period around 14 000 years ago. Several sites show the replacement of cold-adapted species, such as the long-tailed mouse and broad-toothed rat, by the Hasting River mouse, and a decrease in abundance of the smoky mouse. Many of these deposits continued to accumulate up to recent times, and these provide a valuable record of what species were present in their local area until the early period of European settlement. In some

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cases, these historic period assemblages contain a high diversity of species, some of them occurring well outside their current ranges, or in very different habitats from where they are now known to occur. One possible interpretation is that these bone deposits are of ‘mixed’ age, in which case the high diversity might be a product of short-term climatic fluctuations that allowed different species to temporarily inhabit the local area before disappearing and being replaced by others. However, application of modern dating techniques to bones from these deposits has shown that they accurately record what species were present at the sites when Europeans arrived. This indicates that some species that have been considered to have different ecologies could naturally have lived in close proximity to one another at this time (see Chapter 10).

Table 4.2. Some Quaternary/Pleistocene mouse and rat bone and fossil deposits. Site Location Age Rodents present Pyramid North-east ~>20 kya (P) and Bush rat Cave Victoria <10 kya (H) Swamp rat Water rat (P) Fawn-footed melomys (P)# White-footed rabbit rat* Broad-toothed rat Smoky mouse Long-tailed mouse (P)# New Holland mouse Hastings River mouse (H)# Devil’s Lair South-west 12–20 kya Bush rat Western Water rat Australia Hopping mouse* Silky mouse Shark Bay mouse# Western mouse# Heath mouse# Texas Caves South-east Late? Bush rat? Queensland Pleistocene Swamp rat? White-footed rabbit rat* Eastern chestnut mouse Desert mouse# New Holland mouse Hastings River mouse#

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Table 4.2 (continued)

Site Location Age Rodents present Mootwingee Western New Post-colonisation Greater stick-nest rat# South Wales House mouse Fawn hopping mouse# Long-tailed hopping mouse* Plains mouse# Sandy inland mouse Bolam’s mouse# Long-haired rat# Victoria Cave Southern <150 kya? White-footed rabbit rat?* South Broad-toothed rat# Australia Silky mouse Plains mouse# Smoky mouse?# Native Rattus Wombeyan South-east Pleistocene Broad-toothed rat New South Plains mouse# Wales Smoky mouse# Wilgie Mia Central-west 1 kya–present Lesser stick-nest rat* Western Greater stick-nest rat# Australia Hopping mouse Long-tailed hopping mouse* Western chestnut mouse# Shark Bay mouse# Sandy inland mouse Pale field rat Yarrangobilly South-east 150–400 years White footed rabbit rat?# Caves New South Broad-toothed rat Wales Smoky mouse Long-tailed mouse* New Holland mouse Hastings River mouse* Bush rat Swamp rat kya = thousands of years ago (P) Pleistocene only. (H) Holocene only * Extinct; # no longer present in region of deposit

Where did the Australian rodents come from? All Australian rodents belong to the subfamily Murinae and, because this subfamily first appeared as a distinct group in southern Asia, Australian rodents clearly have their origins in this region. The first recognised murine genus, Antemus, is recorded in fossil deposits from Pakistan that

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Figure 4.1 An excavated bone deposit at Yarrangobilly Caves in New South Wales reveals bones regurgitated by owls roosting on rock ledges above. The bottom of the excavation pit is 8600 years old, while the surface is less than 200 years old. The deposit contained the skull of a Hastings river mouse (inset) dated at 160 years old. No individuals of this species have ever been caught within 300 km of the site.

are 13.7 million years old. By 11 million years ago murines had spread to Africa and Europe where they appeared suddenly and then rapidly diversified. There is no fossil evidence to indicate that they had reached South-East Asia by this time, but molecular dating suggests that initial diversification of extant South-East Asian murines may even predate the dispersal to Africa and Europe. Murine rodents may have arrived in New Guinea prior to their invasion of Australia, perhaps as early as eight million years ago. Some New Guinean lineages show similarity to endemic Philippine groups, suggesting this as a possible route of migration. Alternatively, a common ancestral stock for both geographic radiations may have been widely distributed in Indonesia and dispersed northwards and eastwards from there. Although New Guinea is now a very large island, it arose as a series of smaller islands with different geological and geographical origins which subsequently amalgamated. This geological history would have been conducive to the evolution of multiple rodent lineages. Relationships

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1850–1950 Widespread extinctions of populations and species of Australian rodents 1788 Colony of New South Wales established

~10 kya Land bridges between Australian mainland, Mild interglacial Mild interglacial period New Guinea and Tasmania flooded 10 kya

20 kya Height of last Pleistocene glacial period

? Early Pleistocene Native mice of Pseudomys group undergo phase of radiation as arid conditions develop –

Pleistocene hopping mice evolve

Repeated cycles of cold, arid (glacial) phases and exposure of land bridges between Australia, New Guinea and Tasmania Mosaic-tailed rats and ?Early Pleistocene { Prehensile-tailed rat arrive 1.8 Mya ? Late Pliocene Native Rattus arrive

2–3 Mya Oldest Australian water rat fossil

~4.2 Mya Oldest Australian rodent fossils Pliocene

Mild climate. Much of Australia would have experienced wet summers and dry winters. ? 5 Mya Australian Old Endemic rodents arrive and undergo rapid ecological radiation 5.3 Mya

? 8–10 Mya Ancestor of Australo-Papuan Old Endemic rodents arrives in New Guinea Miocene Holocene

13.75 Mya Oldest known fossil Murine in southern Asia Relatively wet and warm Epoch, ended in a cold phase of low sea levels that may have assisted Australia to reach rodents

Figure 4.2 Geological epochs and major events in the evolution of Australian mice and rats. kya = thousands of years ago; Mya = millions of years ago.

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among Australian rodents (Figure 4.3) show that it was one of these New Guinean lineages that first spread to Australia and gave rise to the Australian Old Endemic rodents. Why this group, which presumably had an origin in rainforests, should have so successfully invaded the drier, more open habitats of Australia is unclear. Because of this apparent anomaly, it has been suggested that the early ancestors of the Australian Old Endemics came from the drier islands of eastern Indonesia. However, no close relatives to the Australian rodents have been found on these islands. Instead, fossil rodents from these islands suggest that they had a unique rodent fauna, distinct from that of Australia. The more recent history of the Australian fauna, including rodents, is dominated by multiple crossings of the Carpenterian land bridge that connected New Guinea and Australia during Pleistocene glacial periods when sea level was lower than present. Prehensile-tailed rats, native Rattus and mosaic-tailed rats all may have entered Australia by this route in the early Pleistocene (Fig. 4.2) when rainforests probably extended across the land bridge. Some native Rattus, as well as the delicate mouse, chestnut mouse and brush-tailed rabbit rat, crossed back into New Guinea during periods of low sea level, the last of which ended as recently as ten thousand years ago.

Relationships among Australian rodents Evolutionary relationships between species can be represented by the construction of a phylogenetic tree, which is generally based on similarity of morphology, DNA sequences or other biochemical markers (see Figure 4.3). Among the Australian rodents the Australo-Papuan Old Endemics differ in many ways from the native Rattus, and the two groups are only distant relatives. Such differences include numbers of chromosomes, morphology of the spermatozoon and DNA sequences. The prehensile- tailed rat differs from other Australo-Papuan Old Endemics in the number of nipples in the female, and in chromosome arrangement but is closely related to a suite of other species found in New Guinea. All the remaining Australo-Papuan Old Endemic species are united by their similarity in chromosomes, sperm morphology, blood and other proteins and DNA sequences. Within the Australo-Papuan Old Endemics, the Australian water rat and water mouse both possess a reduced and divergent morphology of

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Native Rattus A–P NEW ENDEMICS Prehensile-tailed rat NG OLD ENDEMICS

Water rat Water rats Water mouse

White-tailed rats Mosaic-tailed

Melomys rats Short-tailed mice

Rock-rats Rabbit rats Tree rats

Stick-nest rats rat clade) (Tree

Hopping mice Australian Old Endemics Broad-toothed rat

Pebble-mound mice OLD ENDEMICS AUSTRALO-PAPUAN

Velvet mice False mice (Native mouse clade) Delicate mice Other native mice

Figure 4.3 A predicted phylogeny based mainly on molecular data and informal nomenclature of Australian rodents. A–P = Australo-Papuan

their molar teeth (see Chapter 6) as well as various adaptations for aquatic life. These features clearly distinguish them as an early divergent lineage. Molecular data show that the relationship between Australian Old Endemics and the mosaic-tailed rats is much closer; it is sometimes difficult to separate these groups when examining DNA sequences and proteins, although their tails differ greatly (Fig. 4.4). Within the Australian Old Endemics four major modern lineages, or clades, occur: the short-tailed mice, the rock-rats, the ‘tree rat’ clade (which

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includes the rabbit rats and stick-nest rats as well as the tree rats) and the ‘native mouse’ clade, within which the broad-toothed rat, hopping mice and other native mice are all included. This latter group constitutes more than half of all the species of Australian native rodents. The native mice have been the most difficult part of the Australian rodent fauna in which to resolve generic and specific relationships. They represent a second phase of evolutionary diversification among the Australian Old Endemic rodents, with most retaining a generalised mouse- like morph ology. Where departures from the ancestral type occur, they are restricted to just a few species such as hopping mice, all of which share a specialised hind limb morphology (see Fig. 4.6), and the pebble-mound mice that all share the unique behavioural trait of pebble mound-building. Based on most molecular studies the ‘false mice’, ‘grizzled mice’ and ‘delicate mice’ appear to be more closely related to each other than they are to the pebble-mound mice or hopping mice, but the relationships between native mouse groups are not fully resolved at the present time. Among the hopping mice, one subgroup that includes all extant species except for the fawn hopping mouse is defined by its highly derived reproductive morphology (see Chapter 5). There are several lineages of native Rattus in Australia. Five species – the canefield rat, pale field rat, long-haired rat, dusky rat and an unnamed species – are closely related and have probably radiated within Australia. The others, including the bush rat, Cape York rat and swamp rat, may each be more closely related to some of the New Guinea native Rattus than to other Australian species. All Australian and New Guinean native Rattus nevertheless appear to be more closely related to each other than any are to the species of native Rattus in Asia, such as the black rat and brown rat. This indicates that the general pattern of evolution among the Australo- Papuan Old Endemics (invasion of Australasia followed by radiations centred in Australia and New Guinea) also occurred in these more recent invaders, the native Rattus.

Adaptations of Australian mice and rats Evolution is generally thought of as adaptation to local conditions. Behavioural changes are often considered to evolve more readily than alterations of physical structures such as limbs or tails. This is reflected in the more recent invasions of rodents into Australia, such as the native Rattus and mosaic-tailed rats which show few, if any, morphological adaptations to

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Figure 4.4 Scanning electron micrographs of a small part of tail (a) plains mouse, showing an abundance of long hairs, typical of most of the Australian old endemics, and (b) a fawn-footed melomys (a mosaic-tailed rat) showing non-overlapping scales and very short hairs; and (c) a native Rattus showing straight, stiff hairs.

Figure 4.5 Hind feet of Australian rodents showing marked variation between species from (a) stick-nest rat, (b) dusky hopping mouse, and (c) a water rat. Note long narrow feet with reduced number of foot pads and short first digit in hopping mouse, and partial webbing between toes II, III, and IV in water rat. From Wood Jones, The Mammals of South Australia

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Australia’s arid environment. Nevertheless, the long-haired rat has evolved a pattern of irruptive reproduction and drought-avoiding behaviour that has allowed it to periodically be very successful in the arid zone. By contrast the Australian Old Endemic rodents, which were already living in Australia before true deserts began to develop, possess physiological adaptations to arid conditions with a few species capable of surviving in the most arid parts of the continent. Hopping mice, in particular, exhibit striking adaptations to arid conditions. Members of this genus have evolved long tails and elongate and narrow hind feet (Figs. 4.5 and 4.6) for energetically-efficient hopping, and they have large, heat-dissipating ears. They also have large auditory bullae around the middle and inner ear (see Fig. 6.3) indicating good detection of low frequency sounds to aid in predator avoidance. Hopping mice and the sandy inland mouse also excrete highly concentrated urine and produce very dry faeces to minimise water loss. Consequently, in the natural environment they do not need to drink to survive. Furthermore, they exhibit marked huddling behaviour, presumably for temperature regulation, when kept in groups (see Chapter 8). A very different example of an extreme form of adaptation is shown by the water rat which has partially webbed hind feet (Fig. 4.5), water repellant fur with a dense undercoat, small ears and eyes, and large whiskers, presumably for detecting prey in the water in which it lives, whereas the large tree rats have long broad feet with prominent pads and very long tails, to aid in balancing whilst foraging in trees.

Diversification of rodents in Australia The three most important phases of diversification leading to contemporary Australian rodent groups are:

• an early to mid-Pliocene radiation of the Australian Old Endemic genera • a late Pliocene/early Pleistocene radiation of the native mice • a Pleistocene radiation of the New Endemics or native Rattus. The Australian Old Endemics are the only group that has undergone significant speciation in Australia, with the species diversity of other groups largely due to multiple invasions from New Guinea. Most species of the Australian Old Endemics occur in the seasonally arid northern savannahs or the central arid zone. Since these regions contain the highest generic and

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Figure 4.6 Hind limbs of (a) plains mouse and (b) spinifex hopping mouse showing the relative lengths of the individual bones. Note that the hopping mouse has comparatively longer metatarsals for rapid bipedal locomotion.

ecological rodent diversity, it is likely that radiation of this group occurred in seasonally dry habitats that dominated central and northern Australia during the Pliocene, despite the fact that rainforest was probably their ancestral habitat. Whether the Australian tropical rainforests were without rodents until the Pleistocene invasion of mosaic-tailed rats, the prehensile- tailed tree rat and native Rattus from New Guinea is unclear, but today few Australian Old Endemics are found in this environment. The Australian Old Endemics represent a modest ‘adaptive radiation’ with each major lineage exploiting a different lifestyle. For instance, large

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tree rats live in trees, medium-sized rock-rats live among rocks and an assortment of native mice occur in various terrestrial habitats. These different groups appear to have evolved rapidly, with species diversity developing by the further splitting of these lineages into multiple species. For example, there are now five species of rock-rat, four species of pebble- mound mice and at the time of European settlement there were two species of stick-nest rat. To put this ecological and morphological diversity of the Australian Old Endemic rodent radiation into some perspective, the group had its origins in Australia at roughly the same time that the highly speciose genus Mus (to which the house mouse belongs) first evolved in Asia. Although Mus contains a large number of species (approximately 42) they are all similar in body size and morphology and show far less ecological diversity than the eight or so genera of Australian Old Endemics that have evolved over the same time period. Exploitation of new lifestyles can also lead to speciation and evolution of new groups within established lineages. A major influence on the evolution of Australian Old Endemic rodents in the late Pliocene and Pleistocene appears to have been the development of arid habitats across much of the country. Although more than half of Australia is now desert, these conditions only developed within the last one or two million years. The loss of forests and woodlands across central Australia was an obvious disadvantage for the tree rats that normally make their nest in tree hollows. However, one lineage within this group, the stick-nest rats, evolved the ability to build fortress-like nests out of sticks (see Chapter 8), thereby creating artificial ‘tree hollows’ in a relatively treeless environment. The native mouse group also seems to have undergone a significant radiation as deserts developed and spread, with the most extreme evolution of adaptations to desert living being seen in the hopping mice. Evolution of new species can also occur due to long-term isolation of populations. Classically, the formation of mountain ranges or ocean barriers results in speciation events. However, in Australia the primary cause of isolation between populations of a species appears to have been the development of arid habitats. Thus, there are populations of closely related species, or subspecies, found on opposite sides of arid barriers in several regions of the continent. For example, two closely related species, the ash-grey mouse of south-west Western Australia and the silky mouse of the south-east of South Australia and western Victoria, are separated

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from each other by the Nullarbor Plain. This arid region also separates two populations of the heath mouse, one of which is present in south-west Victoria and the other in south-west Western Australia. In the north of the country populations of the common rock-rat occurring in the Kimberley and the Pilbara are separated by dune fields of the Great Sandy Desert, and populations of the tropical short-tailed mouse, black-footed tree rat and delicate mouse are all present in the Top End and on Cape York on either side of the Gulf of Carpentaria, without intervening populations in the arid grasslands south of the Gulf. Most of these isolated populations have not yet diverged sufficiently to be treated as separate species. By contrast, large rock-rats that inhabit pockets of moist vine-thicket in the Kimberley, Top End and the Gulf of Carpentaria have diverged to form three distinct species. Yet other species, such as isolated species of pebble- mound mice, have distributions reflecting both climatic factors and their need for stony habitats. Speciation among native Rattus in Australia has been remarkably rapid. They have followed a different path from that of the Australian Old Endemics insofar as these species have speciated primarily through chromosomal divergence. Unlike the chromosomally conservative Australo-Papuan Old Endemics, the native Rattus exhibit considerable chromosomal variation, with examples of different numbers of chromosomes between species. When chromosome rearrangements take place, such as Robertsonian fusions, individuals within a population are likely to have different numbers of chromosomes. When offspring of hybrids of these individuals are produced, they are likely to be sterile due to difficulties of chromosome pairing at meiosis. This can lead to rapid reproductive isolation between sub-populations, one with normal and one with the rearranged chromosomes, with resultant speciation. The dramatic boom-and-bust lifestyle of the dusky rat, long-haired rat and the unnamed species from central Queensland lends itself to fixation of such chromosomal changes in a population since, in small populations such as those that occur after a population crash, a rare mutation may spread by chance alone. Sequencing of rapidly evolving regions of DNA has shown that these species have only recently diverged and chromosomal studies point to Robertsonian fusions as the mechanism that resulted in them becoming separate species. In conclusion it is evident that Australian Old Endemic rodents probably invaded from New Guinea around five to six million years ago.

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The water rat, an Australo-Papuan Old Endemic species. Drawing by Ella Fry.

The group then underwent an ecological adaptive radiation followed by a subsequent phase of speciation within these lineages, primarily due to fragmentation of originally wider distributions. The role of extinction in shaping the modern Australian rodent fauna might have been considerable due to aridification of much of the continent since their arrival. However, to date, the fossil record has revealed few extinct lineages. Further groups of Australo-Papuan Old Endemics, the water rats and mosaic tailed rats, then invaded Australia with little diversification of these groups taking place within the country. Species of native Rattus have not undergone as pronounced an ecological radiation as the Australian Old Endemics. They show few morphological specialisations to local conditions but have achieved species diversity through several invasions from New Guinea, rapid chromosomal evolution and behavioural adaptations.

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Top: Young brush-tailed rabbit rat. This species has grey fur over much of body and a black tail for most of its length. Photo: Sean Flaherty and Bill Breed Bottom: The desert short-tailed mouse has a relatively short tail, rounded ears and white feet. Photo: Peter Canty

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Top: The greater stick-nest rat has a blunt nose, large ears and hind feet, and grey- brown fur. Photo: Peter Canty Bottom: The golden-backed tree rat has a very long tail and golden, light brown fur on its back. Photo: Jiri Lochman/Lochman Transparencies

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Top: The dusky hopping mouse has large eyes and ears, a very long, brush-tipped tail and light, sandy coloured fur. Photo: Uli Kloecker Bottom: The fawn hopping mouse has large ears and eyes, a brush-tipped tail, and light grey fur on its back contrasting with its white belly. Photo: Peter Canty

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Mitchell’s hopping mouse is the largest living hopping mouse species. It has large ears and eyes, and long back feet. Photo: Jiri Lochman/Lochman Transparencies

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Top: The plains mouse has light brown-grey dorsal fur, a large scrotum and a bicoloured tail. Photo: Peter Canty Bottom: Bolam’s mouse used to be confused with the sandy inland mouse (see page 77) but it has darker fur and longer feet. Photo: Tony Robinson

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Top: The silky mouse has light grey fur on its back and white feet. Photo: Tony Robinson Bottom: The smoky mouse has slate-grey hair on its back and a contrasting white belly. Photo: Linda Broome

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Top: The delicate mouse is Australia’s smallest native mouse. Note its very thin tail. Photo: Jiri Lochman/Lochman Transparencies Bottom: The sandy inland mouse has a sandy-brown coloured back and a white belly. Photo: Peter Canty

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The broad-toothed rat has a stout body, short limbs, dark brown fur and a short tail. Photo: Jiri Lochman/Lochman Transparencies

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Top: The western chestnut mouse has light brown dorsal fur and a white belly. Photo: Dave Taggart and Libby Olds Bottom: The western pebble-mound mouse. These animals carry pebbles in their mouths which they arrange around their burrow entrance. Photo: Jiri Lochman/Lochman Transparencies

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Top: The desert mouse has an orange-coloured ring around its eye. Photo: Jiri Lochman/Lochman Transparencies Bottom: The heath mouse has light grey dorsal fur, a grey/white belly and a relatively short tail. Photo: Jim Forrest

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The western mouse lives communally in south-west Western Australia. Photo: Jiri Lochman/Lochman Transparencies

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Top: The common rock-rat has a thickened tail, which can easily break off. Photo: Dave Taggart and Libby Olds Bottom: The Arnhem Land rock-rat has long hairs towards the end of its tail, which is fatter at the base. Photo: Sean Flaherty and Bill Breed

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Top: The fawn-footed melomys has small ears and an apparently hairless tail (see Fig. 4.4). Photo: Bill Breed Bottom: The giant white-tailed rat has grey-brown fur on its back and white fur on its belly. Its tail is grey at the base and white towards the tip. Photo: Mike Cermak

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Top: The water rat has relatively small ears and eyes, prominent whiskers and a thick white-tipped tail, which it uses as a rudder when swimming. Photo: Jim Parke Bottom: The water mouse is considerably smaller than the water rat. It has a grey back and a white belly. Photo: Hans and Judy Beste/Lochman Transparencies

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The prehensile-tailed rat has soft grey fur on its back, pink feet and a prehensile tail. Photo: Hans and Judy Beste/Lochman Transparencies

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Australian native Rattus vary in size and coat colour. The swamp rat (top left) has blackish fur, a short black tail and dark feet. The long-haired rat (top right) has long grey hair on its back and a grey tail. The pale field rat (bottom) has protruding eyes and light yellow-brown fur. Photos: Steve Doyle (top left); Peter Canty (top right); Dave Taggart and Libby Olds (bottom).

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ecause reproduction is central to the survival and evolution of a species, Bthe processes involved are likely to be under strong selective pressure. The commensal species of rodents, such as the house mouse, black rat and brown rat, all exhibit high reproductive potential. Compared with most eutherian mammals, these species have short pregnancies, produce large litters that undergo rapid development and mature at a young age. This results in a short generation time with populations of these species being able to adapt rapidly to changing environmental conditions – a feature that is no doubt one of the reasons why they have spread so successfully to modified human environments around the world. Not all rodents have such a high reproductive rate. For instance, the hystricognath rodents have a much longer gestation period. In guinea pigs and their close relatives it is around 70 days, and it is well over 100 days in many other hystricognaths, with a maximum of around 210 days in the Canadian porcupine. Associated with this, pups of these species are generally much more precocious in their development at birth. Many other rodents have a much smaller litter size than the commensal species. For example, the springhare of southern Africa, the agouti of South America and some dormice species usually produce only one young at a time.

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What are the reproductive rates of the native Australian mice and rats? Are they similar to those of the commensal species? How variable is the reproductive anatomy and physiology between these species given the diversity of habitats in which they occur?

Reproductive biology of the male Testis size In mammals, spermatozoa, after leaving the testis, pass along an extended duct, the epididymis, where they develop potential motility and the ability to fertilise eggs, and are then mixed with secretions from various accessory sex glands (see Figure 5.1) that vary markedly in size across the different orders of mammals. Furthermore within several major groups of mammals there are considerable differences in relative testis size across species. These differences are generally thought to relate to variations in breeding systems. Species that have relatively larger testes tend to be those that occur in multi-male breeding groups where a female is likely to be inseminated by more than one male in a single oestrous period, with the consequence that competition between sperm from the different

Figure 5.1 A dissected male reproductive tract of an adult rodent largely based on the water rat. Note large testes, highly coiled epididymis, and a suite of accessory sex glands that includes seminal vesicles, coagulating glands, prostates, Cowper’s and preputial glands.

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males is likely to occur within the female reproductive tract to fertilise the recently ovulated eggs. In these species selection for maximising testis size is likely to have occurred since, all other things being equal, the male that produces the most sperm is the most likely to fertilise the eggs and thus pass his genes on to the next generation. Conversely, species that occur in monogamous, or single-male mating, groups tend to have a smaller relative testis size due to low levels, or even absence of, inter-male sperm competition. Although the size of the testis and its activity may vary at different times of the year depending on whether or not individuals are reproductively active, most Australian native rodents at times of reproductive activity have a relatively large testis size of around 1% to 3% of body weight, which is similar to that in many other species of mice and rats occurring in Asia and Africa. Associated with this, very large numbers of sperm are produced suggesting that a polygamous or promiscuous mating system occurs in these species. Male delicate mice, silky mice and heath mice, however, all have somewhat smaller testes of around 0.5% body weight, with the heath mouse being one of the very few species of native rodents where field data have suggested a monogamous mating system. Nevertheless the smallest testis size is present in four of the five extant species of hopping mice (see Fig. 5.2). The spinifex hopping mouse, for instance, has a testis mass of

Figure 5.2 Log of testis mass plotted against log of body mass for sexually mature Australian rodents; note position of three hopping mouse species.

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only around 0.1% to 0.2% of body weight which is an order of magnitude smaller than that which occurs in other rodents of similar body size. Of the five living hopping mouse species, only the fawn hopping mouse has somewhat larger testes. Such a small testis size does not occur in any other species of mouse or rat. Furthermore, in the spinifex hopping mouse the dynamics of sperm production within the testis itself have been found on a per gram of testis mass basis to be low. Thus the efficiency of sperm production is less than that in species with larger testes. These findings indicate that far fewer sperm are produced in adult male spinifex hopping mice compared to species in other genera. They clearly suggest a relaxation of selection for maximising sperm production in these species and thus the occurrence of a mating system with minimal inter-male sperm competition.

Sperm morphology The actual size and shape of the spermatozoa also show con siderable variation between species of mammals with a tendency for there to be smaller sperm in species with a larger body mass. Most mice and rats have large sperm, and the Australian native Rattus have a sperm head that has a characteristic hook shape (Figure 5.3a) in which there is a complex arrangement of intracellular components including the nucleus. However, most of the Australo-Papuan Old Endemics, including water rats, mosaic- tailed rats as well as most species of the Australian Old Endemics, have a more complex sperm head, with two additional processes extending from its upper concave surface (Figure 5.3b and 5.3c). These processes may bind the spermatozoon to the egg coat (the zona pellucida) around the time of fertilisation, which is essential if egg coat penetration and fertilisation is going to occur. This characteristic sperm morphology is also present, albeit in reduced form, in three species of forest mice in the genus Apomys in the Philippines. It may thus have evolved in a common ancestor of these forest mice and Australo-Papuan Old Endemics. In spite of the widespread occurrence of this sperm type in the Australian Old Endemics, there are a few species in two of the native mouse groups, as well as in the hopping mouse lineage, which have evolved a very different sperm structure. The most divergent of these is in the delicate mouse of the Northern Territory and North Kimberley where the sperm head is pear-shaped (Figure 5.3d), and the heath mouse where it is paddle-shaped (Figure 5.3e) with sperm morphology in these species showing convergence to that in other orders of eutherian mammals.

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Figure 5.3 Sperm heads of Australian rodents differ dramatically across species. In native Rattus there is a single long apical hook (a), whereas in most of abc the Old Endemics the sperm head has two extra processes that extend from the upper concave surface as shown for Mitchell’s hopping mouse (b) and giant white-tailed rat (c). Within native mice a few species have very different sperm head shapes as shown by that of the delicate mouse (d) and heath de mouse (e).

Male accessory sex glands When spermatozoa are passed from the male to the female at the time of mating, they are mixed with secretions from the accessory sex glands of the male reproductive tract. Early observations of various New World rats and mice showed that most species in this group have a complex suite of accessory sex glands which include, among others, large seminal vesicles and coagulating glands (see Figure 5.1), the secretions of which form a hard intravaginal plug after insemination. This plug aids in the transport of sperm through the cervix and also probably reduces the chances of sperm from any subsequent males that mate with the female at the same oestrous period from reaching the upper parts of the female tract and fertilising the eggs. Among the Australian mice and rats, all the native Rattus, together with most of the Australo-Papuan Old Endemics, have large seminal vesicles and coagulating glands (Table 5.1, Figure 5.4a) and, associated with these, a large intravaginal plug is formed after insemination. Nevertheless, studies with laboratory-maintained plains mice have demonstrated that this does not totally prevent sperm from other males that mate with the female during the same oestrous period from fertilising the eggs. In hopping mice, there is however a very different arrangement of accessory sex glands where just one large gland, the ventral prostate, is present with the seminal vesicles, coagulating glands and dorsal prostates all being very small (Figure 5.4b, Table 5.1) and, in these species, no large intravaginal plug is formed postcoitum.

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The other accessory sex gland that varies greatly in size and shape between species of mice and rats is the preputial gland which, if present, lies on either side of the prepuce of the penis (Figure 5.1). In the house mouse, where its function has been investigated in some detail, it has been shown to produce volatile chemical compounds, or pheromones, which elicit agonistic interactions in cohabiting males. In Australian mice and rats, no studies have been performed on the function of this gland, but large interspecies differences occur in its size, with it being especially large in western chestnut mice, but minute, or even non-existent, in hopping mice, melomys and water rats (Table 5.1). Male western chestnut mice show far higher levels of aggressive behaviour than do most other species

Table 5.1 Relative size of male accessory sex glands in Australo-Papuan Old Endemics. Genus Seminal Coagula- Dorso- Ventral Ampul- Bulbo- Preputial vesicle ting lateral prostate lary urethral prostate Plains ++ ++ ++ ++ ++ ++ ++ mouse Western ++ ++ ++ ++ ++ ++ +++ chestnut mouse Desert ++ ++ ++ ++ ++ ++ ++ short- tailed mouse Fawn ++ ++ + +++ + ++ + hopping mouse Spinifex ++++++++++ hopping mouse Giant ++ ++ ++ ++ ++ ++ 0 white- tailed rat Fawn- ++ ++ ++ ++ ++ ++ 0 footed melomys Water rat ++ ++ ++ ++ ++ ++ 0 Water ++ ++ ++ ++ ++ ++ ? mouse + Present but very small ++ Present and of average size +++ Present and unusually large 0 Absent ? Not known

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Figure 5.4 Male accessory sex glands from two species of Australian Old Endemic rodents. Those from a plains mouse (a) and spinifex hopping mouse (b). In the plains mouse there are large coagulating glands (CG) and seminal vesicles (SV), but modest development of the ventral prostates (VP) and dorsal prostates (DP). In the hopping mouse, by contrast, the seminal vesicles (SV), coagulating glands (CG) and dorsal prostates (DP) are very small but ventral prostates (VP) are very large. Note also the wider vas or ductus deferens (DD) in the latter species which acts as an accessory sperm store; AG = ampullary glands; BG = bulbourethral glands.

of native mice and rats. This may relate to the secretory activity of the large preputial glands that occur in these animals.

External genitalia and mating behaviour The structure of the penis varies considerably in size and shape across species of mammals. In mice and rats it is generally barrel-shaped with small spines on its surface made up of cornified cells and, as in carnivores and some primates, it contains a bone or baculum. A similar penis structure occurs in most of the Australo-Papuan Old Endemic rodents (Figure 5.5a) as well as in the native Rattus. However, in most hopping mice species, the penis has a narrow shaft and thin baculum, but much larger spines (Figure 5.5b). This divergent morphology of the male external genitalia in hopping mice is associated with the structure of the vagina where the lumen is very narrow and an unusually thick muscle coat occurs. These complementary morphological features of male and female reproductive anatomy in hopping mice are associated with the occurrence of locking that takes place at the time of mating. Such mating behaviour is rare in rodents and may relate to the efficient sperm transport that occurs in this species.

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a b Figure 5.5 Glans penis, as shown by scanning electron microscopy, together with the associated bone or baculum of a sandy inland mouse (a) and spinifex hopping mouse (b). Note that the penis of the hopping mouse, which locks in place during mating, has much larger surface spines and a thinner baculum.

Reproductive biology of the female The female reproductive tract consists of a pair of ovaries where the female germ cells, the eggs or oocytes, develop within ovarian follicles. Periodically varying numbers of eggs (Figure 5.6) are ovulated and pass into the open end of the oviducts. If fertilisation takes place, this occurs in the upper reaches of the oviduct with the spermatozoon first having to pass through the surrounding egg coat (the zona pellucida). The resultant embryos then pass into the uterus which, in mice and rats, has two separate horns – a structure that is known as a duplex uterus (Figure 5.7). The uterine horns converge at the highly fibrous cervix which is generally similar in structure across the Australian mice and rat species except in hopping mice where it is less fibrous and more muscular.

Ovulation rate and litter size The number of eggs released at ovulation (the ovulation rate) determines the resultant litter size. In house mice there are generally between 6 and 10 eggs ovulated and a litter size of similar number occurs, although in a few species of hystricognath rodents, far more eggs are ovulated than there are pups born. The multimammate mouse of southern Africa, Mastomys natalensis, probably has the highest ovulation rate of any species of mouse

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or rat. It has no fewer than 22 nipples and may have a litter of up to 17 pups at the one time. In the Australo-Papuan Old Endemics, the average number of eggs ovulated and potential litter size is much smaller and generally around three or four (Figure 5.6), with the litter size of species that occur in rainforests tending to be less than those in the arid and semiarid regions, e.g. mosaic-tailed rats usually have only one or two pups at a time (Table 5.2). All species of Australian Old Endemics have only four nipples all of which are in the lower abdominal and inguinal region. In contrast to the Old Endemic groups, the native Rattus generally have a higher ovulation rate and among these species there are differences, not only in the number of eggs ovulated, but also in the number of nipples present. Species occurring in grassland, or deserts (i.e. the long-haired, dusky and canefield rats) have an average ovulation rate of between six and 10 with these animals having 12 nipples (Table 5.2), six in the pectoral and six in the abdominal region. The bush and swamp rats, as well as the pale field rat, generally have an ovulation rate of five or six although it varies somewhat between, and even within, populations, with the females having eight or 10 nipples. The lowest ovulation rate among the native Rattus occurs in the Cape York rat where it is generally three or four with females of this species having only six nipples. This results in the smallest litter size of any Australian species of Rattus and is similar to that of the true rats occurring in the rainforests of South-East Asia.

Figure 5.6 Recently ovulated eggs from oviduct of a hopping mouse (a); a spermatozoon (arrow) is bound to the outer surface of the egg coat (b).

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Table 5.2 Reproductive biological characteristics of female Australian native rodents. Species Average Number Approx. Prolonged Approx. litter of duration of pup age of size nipples pregnancy attachment weaning (days) to nipple (days) White-footed 2–3 4 36 Yes 20 rabbit rat Desert short-tailed 3–4 4 35 – 28 mouse Greater stick-nest rat 2 4 44 Yes 30 Broad-toothed rat 2–3 4 39 – 35 Black-footed tree rat 2 4 43 Yes 42 Spinifex hopping 3–4 4 32 No 30 mouse Fawn hopping 3 4 40 No 28 mouse Dusky hopping 3 4 34 No 28–30 mouse Mitchell’s hopping 3–4 4 32 No 35 mouse Silky mouse 4 4 38 – 40 Plains mouse 4 4 30 Yes 28 Delicate mouse 3 4 31 – 30 Desert mouse 3 4 28 – 20 Sandy inland mouse 3–4 4 31 Yes 30 Long-tailed mouse 3–4 4 32 Yes 25 Western chestnut 3 4 24 Yes 15–20 mouse New Holland mouse 3–4 4 33 Yes – Common rock-rat 2–3 4 34 – 28 Fawn-footed 2438Yes20 melomys Grassland melomys 2–3 4 – Yes – Giant white-tailed rat 2 4 41 Yes – Water rat 4 4 34 No 29–34 Dusky rat 9 12 22–23 No 20 Bush rat 5 10 23 No 31 Cape York rat 3–4 6 23 No 25–30 Swamp rat 4–6 10 21–23 No 21 Canefield rat 7–8 12 21–23 No 20 Long-haired rat 8–9 12 22–23 No 21 Pale Field rat 4–5 10 22 No 21 – = unknown

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Figure 5.7 Dissected reproductive tract of a spinifex hopping mouse showing two uterine horns and small cervix.

Figure 5.8 Average litter size of Australo-Papuan Old Endemics is low and rarely exceeds 4, whereas that of most species of native Rattus, South-East Asian murines and African murines is considerably greater in many species.

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Clearly, most of the Australian native Rattus have the potential to ovulate more eggs and suckle more young than the Old Endemic rodents, with ovulation rates and associated litter sizes generally being somewhat smaller in forest species than those living in grasslands or deserts. The high potential reproductive rate of grassland and desert species of native Rattus gives them the capacity for rapid population increase in response to a superabundance of resources. This results in the periodic occurrence of very high numbers of long-haired and dusky rats. It was such ‘plagues’ of long-haired rats that so impressed some of the early European explorers in the Lake Eyre region of South Australia. The dusky rats at Fogg Dam on the Adelaide River near Darwin have been studied in detail and they too, at times, can become extremely abundant.

Pregnancy length and lactation The pregnancy length of house mice and both black and brown rats is about 20 to 23 days. However, in water rats, melomys, most of the native mice and hopping mice, pregnancy is considerably longer and in most species of Old Endemics, it is around 32 to 35 days (Fig. 5.9) with both the length of time from fertilisation to implantation, as well as the period from implantation to birth being considerably longer than in the house mouse. Nevertheless, newborn pups of the spinifex hopping mice are similar in their development to those of house mice indicating a slower

Figure 5.9 Average gestation in the Australo-Papuan Old Endemics is considerably longer than that of most native Rattus and other South-East Asian murines.

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intrauterine growth rate in the native species both prior to, and following implantation. In some of the Old Endemic native rodents such as hopping mice, females already suckling pups from a previous litter have an increase in gestation length of several days due to a lactational delay of implantation. This enables the mother to replenish her body condition after raising the young of the previous litter before giving birth to a subsequent group of pups. Such a delay of implantation due to suckling, or embryonic diapause, is common in various species of mice and rats but does not seem to occur in plains mice or western chestnut mice. Although pregnancy length in nearly all of the Old Endemics is 30 or more days, it is only around 24 days in the western chestnut mouse. At the other extreme, two species of tree rats, the stick-nest rat, fawn hopping mouse and giant white-tailed rat all have a pregnancy length of between 40 and 46 days. Once born, marked differences occur in the behaviour of the pups of different species of Australian mice and rats. In many of the Australo- Papuan Old Endemics, but not in the native Rattus, the young cling to the nipples of the mother for much of the time. However, this appears not to be the case for hopping mice, water rats and rock-rats, where the mother leaves the pups in the nest when she emerges to forage. In spinifex hopping mice not only the female, but also the male, will retrieve pups if they wander from the nest, thus demonstrating some degree of paternal care in these animals (Figure 5.10). In the Australo- Papuan Old Endemics the length of time it takes for pups to mature is generally around 60 days, although in the western chestnut mouse is unusually short with some females starting to ovulate at around 40 days of age. This rapid maturation presumably results in the young of the year being able to reproduce in the same season in which they were born. In most native Rattus species, the age of maturation is around 70 to 100 days, but the dusky rats can mature at a very early age, with reproduction first taking place in animals as young as four to five weeks of age. Such a rapid rate of maturation is no doubt in part responsible for the rapid increase in population density that can occur. In conclusion, it is evident that there are a number of differences in reproductive biology between the major groups of Australian rodents with the Australo-Papuan Old Endemics having a much lower reproductive rate than the native Rattus. The male reproductive system varies across species with most hopping mice having very small testes and producing

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Figure 5.10 Spinifex hopping mice pups tend to wander from the nest at a young age. When this happens an adult of either sex retrieves them. Photo: Tavik Morgenstern

relatively few sperm. In the Old Endemics, with the notable exception of the western chestnut mouse, pregnancy length is considerably longer than that of native Rattus. Furthermore, the Australo-Papuan Old Endemics generally have a lower ovulation rate, smaller litter size, and invariably have only four nipples. In contrast, in the native Rattus there are one to three pairs of nipples in the pectoral region, as well as three pairs in the lower abdominal region. Interspecies differences occur in the ovulation rate, with it being highest in the three grassland species where 12 nipples are available for suckling pups. Finally, most hopping mice have a suite of highly unusual morphological features of both the male and female reproductive tracts. The reasons for this are not clear at the present time but some of them relate to the occurrence of locking at the time of mating.

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n order to grow, reproduce and maintain a constant body temperature, Imammals must consume food as a source of energy. The shape and arrangement of a mammal’s teeth, as well as the characteristics of its gastrointestinal tract, are likely to relate to the type of food that it eats. Rodents probably evolved from omnivorous or insectivorous mammals that lived at the time of the dinosaurs. However, seed-eating species had evolved by around 50 million years ago. Food from plants is far more abundant than that from animals but its energy content is lower and nitrogen from leaves and stems is not so readily accessible due to their tough fibrous cell walls. Many large plant-eating mammals obtain nutri- ents by fermentation of the plant material in either the foregut, as do ruminants such as cows, sheep, kangaroos and colobus monkeys, or in the hindgut, like horses, rhinos, rabbits and wombats. Rodents have also evolved a variety of strategies for digesting plant material including various dental and gastrointestinal tract adaptations.

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Diet of Australian mice and rats Like the rodents of millions of years ago, the diet of many species of living Australian rodents includes insects and seeds. However, the species with a large body mass often have more specialised diets, for example tree rats are frugivorous (fruit-eating), broad-toothed rats are herbivorous, and water rats carnivorous. Those species with a small body mass require more nutritious food which is essential to maintain their basal metabolic rate, thus, these species tend to consume seeds since these are more nutritious than most other available foods. Some Australian mice and rats show a tendency towards being opportunistically omnivorous and therefore have quite variable diets, with many species eating fungi, insects and fruit, as well as large numbers of seeds. Although many native rodents consume a broad range of food items, some change their diet between seasons according to food availability while others with more specialised diets, tend to eat similar foods throughout the year. Table 6.1 summarises the diet of various species of Australian rodents. Among the Australian Old Endemics that occur in south-eastern Australia a few species change their diet from summer to winter. For instance, the New Holland mouse mostly eats seeds in summer, but in winter broadens its diet to include more leaves and plant stems. Likewise, the diet of the silky mouse and smoky mouse changes from mainly seeds and fruit in summer to a range of foods in winter that includes flowers, insects, fungi and spore cases (sporangia). In contrast to these species, the Hastings River mouse appears to have a broader diet in summer, which includes both leaves and seeds, whereas in winter it has been found to eat mostly leaves. In the arid zone, species such as the spinifex hopping mouse and sandy inland mouse were originally thought to be largely granivorous like many of the desert rodents on other continents, such as kangaroo rats of south- west North America, and gerbils and jerboas of North Africa. However, it is now clear that these Australian desert species differ in having a much broader diet that includes fungi, leaves, stems, roots, seeds and insects, depending on availability. They are thus classified as opportunistic omnivores. Other arid zone species have a more specialised diet, for example, the desert mouse eats mainly leaves and stems of grasses and is thus a herbivore, whereas the central rock-rat has been reported to be a specialist granivore.

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Table 6.1 Dental formula and diet of selected species of Australian rodents. Species Dental formula Diet Dietary classification Silky mouse 1/1 0/0 0/0 3/3 Leaves, stems, flowers, Omnivore seeds, invertebrates Spinifex 1/1 0/0 0/0 3/3 Plants, leaves, roots, Opportunistic hopping mouse stems, spiders, insects, omnivore fungi, seeds Sandy inland 1/1 0/0 0/0 3/3 Seeds, insects, dicot Opportunistic mouse leaves, roots, flowers omnivore Desert short- 1/1 0/0 0/0 3/3 Seeds, green Omnivore tailed mouse vegetation, arthropods Desert mouse 1/1 0/0 0/0 3/3 Seeds, plant material Opportunistic omnivore Broad-toothed 1/1 0/0 0/0 3/3 Mainly grass and dicot Specialist rat leaf; seeds herbivore Greater stick- 1/1 0/0 0/0 3/3 Leaves & fruits of Herbivore nest rat succulent plants especially chenopods, nitre bush Black-footed 1/1 0/0 0/0 3/3 Mainly fruit, especially Mainly frugivore tree rat pandanus, and large seeds; few termites and molluscs Giant white- 1/1 0/0 0/0 3/3 Fruit, seeds (including Opportunistic tailed rat coconuts), birds eggs, omnivore fungi, arthropods Fawn-footed 1/1 0/0 0/0 3/3 Leaves, shoots, seeds, Herbivore melomys fruit Water rat 1/1 0/0 0/0 2/2 Yabbies, shrimps, Opportunistic insect larvae, dytiscid carnivore beetles, mussels, perch, goldfish, odonata nymphs Water mouse 1/1 0/0 0/0 2/2 Crustaceans especially Carnivore small crabs, polyclads, marine pulmonates Bush rat 1/1 0/0 0/0 3/3 Stems, fungi, Omnivore monocots, dicots, insects Swamp rat 1/1 0/0 0/0 3/3 Rushes, grass stems, Herbivore roots, leaves

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The broad-toothed rat, which occurs in the southern Alps and in the button grass plains of Tasmania, is the most specialised herbivore of all the Australian rodents. These animals, with a body weight of around 120 g, consume predominantly fibrous plant material throughout the year with one study showing that grass formed from 52% to 87% of their total diet. The teeth of this species have evolved a unique form that relates to this highly fibrous diet (see below). The greater stick-nest rat is also largely herbivorous and, on Franklin Island where it has survived until the present day, it eats mainly leaves and fruits of succulent plants and herbs, especially of chenopods and the nitre bush. In northern Australia there appear to be several species that are mainly granivorous. These range in size from the very small delicate mice to the large rabbit rats, with the latter species eating mainly grass seeds, although leaves apparently also form part of their diet. The black- footed tree rat, which is the largest member of the Australian Old Endemic group appears, from an analysis of its scats, to be largely a frugivore with the fruits of pandanus being a regular component of its diet. In the rainforests of north-east Queensland, the giant white-tailed rat is also a fruit-eater, but it has more of an omnivorous diet than the tree rat. Its diet includes fruit, nuts, insects and probably small vertebrates, as well as eggs when the opportunity arises, whereas the related melomys species appear to be more generalist herbivores, eating leaves, shoots, roots and fruits. Among the Australian native mice and rats the most unusual dietary specialists are the water rat and water mouse. These species are carnivorous even though they totally lack both the canines and the specialised cheek teeth (the carnassials) of land-dwelling carnivores, such as cats and dogs, that are used for shearing flesh. Water rats eat predominantly freshwater crustaceans such as yabbies and shrimps, insect larvae, dragonfly nymphs and dytiscid diving beetles, and will opportunistically take a variety of vertebrate prey including freshwater perch, goldfish, mosquito fish and, given the chance, even the occasional bird or small mammal. These animals are excellent swimmers and use their thick dense tail as a rudder as they search for food items along rivers and creeks, frequently diving under water for prey. Water rats use feeding tables, such as logs or boulders along rivers and creeks, on which the remains of invertebrate exoskeletons are often left after they have devoured the flesh of the animals.

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The water mouse, which lives in the sublittoral zone of mangrove swamps in Queensland and the Northern Territory, eats mainly small crabs, polychaetes, marine bivalves and marine snails (or pulmonates). Observations of feeding habits of individuals of this species have shown how they disarm a crab by first removing its legs, lunging forward to bite the basal attachment of the claw and then severing it. The water mouse then seizes the unarmed crab from behind, turns it on its back and eats its fleshy body parts. Among native Rattus, the bush rat is one of the most adaptable of the Australian native rodents and has a varied diet that includes fungi, stem and leaf material, seeds as well as insects. By contrast, the swamp rat, which occurs in swampy areas and wet heaths, is more of a dietary specialist and is primarily herbivorous, favouring the stems of grasses and sedges. The canefield rat, which occurs in north Queensland, is one of the few species of native rodents that has become an agricultural pest as it has developed a liking for sugar cane. The animals gnaw at the stems of these plants thus allowing micro-organisms to enter the damaged site so reducing the health of the plants.

Variation in dental morphology A key feature of mammals is the fact that different sizes and shapes of teeth occur in different parts of the jaw. There are generally four types. Passing from the front to the back of the jaw these are the incisors, canines, premolars and molars. The numbers of each of the four types of teeth in a species is indicated by its dental formula. That of the early placental (eutherian) mammalian ancestors was 3/3 incisors, 1/1 canines, 4/4 premolars and 3/3 molars, with the first figure being for the number of respective types of teeth on each side of the upper jaw and the lower figure for the lower jaw. This ancestral dental formula is retained in many insectivores living today, such as some species of shrews, hedgehogs and moles. Most other groups of mammals, however, have a modification and reduction of this number of teeth. Rodents have highly specialised teeth and, unlike most mammals including ourselves, they do not have any canines. The number of premolars is also reduced with one or two pairs occurring in hystricognath rodents, such as guinea pigs, as well as in kangaroo rats, beavers and squirrels. In some hystricognath species the premolars are ‘molariform’ –

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they have a similar form to the adjacent molars. However, none of the mice and rats, including all those occurring in Australia, have any premolars (see Table 6.1). These species thus have just two types of teeth – incisors for obtaining the food and molars for grinding. There is a large gap (the diastema) between the incisors and the molars that occur towards the back of the jaw (Figure 6.1). Apart from the reduction in numbers and types of teeth, mice and rats have incisors that are deep-rooted (Figure 6.2) and grow continuously throughout life. They have a sharp cutting front edge, are chisel-like due to only the front surface having a layer of enamel which is more resistant to wear and tear than the dentine which occurs on the lingual surface. Like other Asian and African murines, most of the Australian mice and rats have a row of three molars on each side of the jaw. During murid evolution there has been a tendency towards a reduction in size of the second, and especially the third molar. However, among many of the Australian Old Endemics, unlike the house mouse, the combined occlusal

Diastema M3 M2 M1 (a) Auditory bulla Glenoid fossa Incisor

Dentine

Incisor Diastema M2 M1 Enamel (b)

Figure 6.1 X-Ray micro CT scan of side view of the skulls of brown rat (a) and water rat (b) showing chisel-shaped incisor with a layer of enamel at the front and dentine internally with a large gap (diastema) between the incisors and molars. In the brown rat the three molars (M1, M2, M3) decrease in size from front to back, whereas the water rat has only two molars with the first molar (M1) being especially large. The skull of the water rat is flatter and longer and has small auditory bullae compared to many native mice and rats (see Figure 6.3).

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Figure 6.2 A lateral X-ray of front part of a spinifex hopping mouse’s skull showing the deep root of the incisor (arrows) which grows continuously as it gets worn away at its surface.

surface area of second and third molars is often as great as, or even slightly greater than that of the first molar. By contrast, the two carnivorous species – the water rat and water mouse – have only two pairs of molars on each side of the jaw (Table 6.1, Figure 6.1b), with a related New Guinea species of shrew mouse, Mayermys, being unique in having just one pair of molars on each side. Why such a reduction in number of molars has evolved is not clear. In rodents, in order for the incisors to become engaged, the superficial masseter muscle that passes from the lower jaw to the side of the skull, contracts. This engaging of its incisors thus enables the animal to gnaw. Once food has been obtained, this muscle relaxes, so the lower jaw moves back and engagement of the molars ensues, allowing grinding of the food. In order for these two types of teeth to be used separately, the glenoid fossa at the base of the zygomatic arch of the skull has an elongate, rather than a transverse, socket (see Figure 6.1a) along which the lower jaw bone moves when the superficial masseter muscle contracts and relaxes. The molars of insectivorous, granivorous and omnivorous species typically have a series of cusps (pointed projections) on the biting surface of the tooth which can become worn down with age (Figure 6.3a). Among

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Australian rodents there are several relatively minor variations in the number and placement of these cusps with either two or three outer (labial) cusps on the first two upper molars, depending on species. In the stick-nest rat the molars have well-developed internal cusps (Figure 6.3b), whereas in the herbivorous broad-toothed rat the cusps have become joined together to form complex ridges and sloping laminae (Figure 6.3c); an arrangement that is similar to some of the herbivorous rodents of the northern hemisphere. Furthermore, unlike all other Australian rodents, the third molar in the broad-toothed rat is as large as, or even a little larger than the second, with the width of the second molar exceeding its length. This broadening of the molars results in a larger surface area for chewing and is clearly an adaptation for eating tough, fibrous grasses and sedges that form most of the diet of this species. Less extreme broadening of the molars is evident among other species with herbivorous tendencies, such as the western and eastern chestnut mice and the Hastings River mouse (see Chapter 4). In the mosaic-tailed rats, the giant white-tailed rat and melomys, the cusps tend to be joined transversely (Figure 6.4a), with an extreme type of specialisation of the cheek teeth being shown in the water rat, as well as its New Guinea relatives, where the molars have a central basin-like depression with an elevated ridge around the periphery (Figure 6.4b). This results in these teeth having an efficient cutting surface for mastication of exoskeletons of crustaceans, insects and hard-shelled molluscs upon which these animals feed. The prehensile-tailed rat that lives in the canopy of the rainforests of north-east Queensland and may be a partial leaf eater (folivore), has rows of three sharp cusps on its molars (Figure 6.4c). How much this is due to retention of a primitive condition rather than dietary specialisation is not clear.

Variation in gastrointestinal tract morphology When rodents first evolved they probably ate a largely proteinaceous diet. However, the universal availability of plant material provided abundant opportunities for these species to develop a herbivorous diet and rely

Figure 6.3 (opposite) X-ray micro CT scan of upper molars of upper jaw of (a) a spinifex hopping mouse with worn cusps; (b) a greater stick-nest rat with a prominent inner cusp on the first molar (arrow); and (c) a broad-toothed rat with very wide molars. Note the relatively large auditory bullae (AB) in the skulls of the first two species.

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increasingly on starch and cellulose obtained from plants. Hence, there would have been strong selective pressure on the gastrointestinal tract to adapt for more efficient utilisation of this food source. Most rodents have two clearly demarcated regions of the stomach. The first region, the corpus (forestomach) into which the oesophagus generally empties, is lined by several layers of superficial, cornified cells (a stratified squamous epithelium) rather like that of the outer layer of the skin; whereas the second half of the stomach, the antrum, is of more typical structure in having a simple columnar glandular epithelium and secretes proteolytic enzymes for digestion of proteins. The function of the corpus has been an area of debate, but its most likely function is to prolong the period of time that amylases, which are secreted by the salivary glands and mixed with food in the mouth, can act to break down starch and glycogen. In mammals, the relative lengths of the small and large intestines, as well as the size of the caecum, vary markedly across species. Herbivores tend to have a relatively long large intestine with a large caecum, which may be sacculated with folds and papillae to increase its surface area. In the caecum, fermentation of fibrous plant material and degradation of cellulose is brought about by symbiont bacteria and protozoa. Processed food material may then be passed through the gut a second time when the animal ingests its faeces, a process known as coprophagy, enabling subsequent absorption of nutritionally valuable components released by fermentation in the caecum. What variations are there in the gastrointestinal tract of the Australian mice and rats, bearing in mind the variety of diets eaten by these species? Among the Old Endemics, the relative areas of the corpus and antral regions of the stomach, the relative lengths of small and large intestines and the relative size of the caecum, all show marked differences across the species. In the small, omnivorous rodents, such as the hopping mice, sandy inland mouse and silky mouse, there are roughly equal areas of the non-glandular corpus and glandular antral regions of the stomach (Figure 6.5a). However, in the more herbivorous species, such as the greater stick-nest rat, the corpus makes up about 65% of the total

Figure 6.4 (opposite) X-ray micro CT scan of molars of upper jaw of (a) a giant white- tailed rat with cusps joined transversely; (b) a water rat where molars have ‘basin- shaped’ depressions; and (c) a prehensile-tailed rat where rows of three prominent cusps are present on the first two molars.

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stomach area. Melomys have an even larger relative area of the forestomach (Figure 6.5b), whereas the frugivorous and herbivorous giant white-tailed rat has a very large stomach with the nonglandular corpus region also making up around 65% of the total surface area. Like

Figure 6.5 Line drawings of comparative morphology of stomachs of four species of native rodents. In those of a Mitchell’s hopping mouse (a) about half of the stomach is composed of the corpus region and half the antrum. In the fawn-footed melomys (b) and the giant white-tailed rat (c) there is a much larger corpus with an extended fundic diverticulum (arrows) in which storage of nonfibrous plant material probably occurs. By contrast, in the water rat (d) the stomach is relatively small and proportionately has a much larger antrum compared to the corpus region.

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in melomys, it extends into a large fundic diverticulum (Figure 6.5c). In addition, the giant white-tailed rat also has a groove, or gastric sulcus, that passes from the base of the oesophagus to the antral region of the stomach, which may allow food to be selectively passed to either the corpus of the stomach or antrum. A study of the distribution of food contents in the stomach of this species has shown that the corpus appears to be a storage site and contains larger food items than the antrum. These food items include fungal spores attached to fruiting bodies, together with nuts and fruits from rainforest trees. Spores, which may be stored for some time in the foresomach, then pass through the digestive tract and are thus returned to the soil in faeces. The pattern of foraging by these animals will thus determine the dispersal of spores on the surrounding forest floor. In the carnivorous water rat, which has a similar body weight to that of the giant white-tailed rat, the stomach is much smaller (Figure 6.5d). Furthermore, only about 25% of its volume is made up of the corpus with the rest being composed of a typical antral glandular lining. This is a markedly smaller relative volume of the corpus than in the herbivorous, or even omnivorous, native rodents. A comparison of the relative lengths of the small and large intestines shows that in the giant white-tailed rat and melomys the small intestine is only about half of the total length of the intestine. In contrast, the relative proportions of the small and large intestines are very different in the water rat, where the small intestine makes up around 90% of the total intestinal length. The relative size of the caecum is also markedly different across species of Australian rodents. It is comparatively small and unfolded in hopping mice, whereas in herbivorous species such as the greater stick-nest rat (Figure 6.6a) and broad-toothed rat (Figure 6.6b), it is comparatively large and highly folded, presumably to increase the surface area for microbial fermentation of cellulose. The caecum is also relatively large in species such as the brush-tailed rabbit rat, the black-footed tree rat, the grassland melomys and the giant white-tailed rat (Figure 6.6c). By contrast, in the carnivorous water rat the caecum is quite small and not markedly folded (Figure 6.6d). In conclusion, it is apparent that in Australian native mice and rats the dental anatomy, the relative size and proportions of the stomach and the relative lengths of the various regions of the intestine and size of the

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Figure 6.6 Caecum from (a) stick-nest rat, (b) broad-toothed rat, (c) giant white-tailed rat and (d) water rat.

caecum, all vary considerably among species. These differences relate to the different foods that the animals eat. Herbivorous species may have unusually broad molars (broad-toothed rat); a very large forestomach (mosaic-tailed rats); a relatively short small intestine; and long large intestine with a large caecum, for maximising microbial digestion of cellulose. By contrast, the carnivorous water rat has molar teeth with basin-shaped crowns and a relatively small stomach which has a pro- portionally smaller relative volume of the corpus, but has a relatively long small intestine and short large intestine with small caecum.

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he unpredictable Australian environment presents significant Tchallenges for small mammals across much of the continent. To combat this many species of native mice and rats maximise their ability to adapt to current conditions by breeding rapidly when conditions are favourable. Although most Australian native mice and rats cannot reproduce as rapidly as some other rodents groups (particularly some of the murids in other parts of the world), they too typify this lifestyle. However the population density of most Australian species is generally low and their occurrence across the landscape is patchy, with peaks in density determined by various environmental factors.

Movements and home ranges Movements of native mice and rats are generally of two types. First, there are those that take place within a small area, or home range. These tend to be structured around areas that provide food, shelter and mating opportunities, although such resources are not necessarily uniform in space and time. Nearly all species are nocturnal, although water rats

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commonly forage during the early morning and late afternoon, and desert mice have sometimes been trapped during daylight. Secondly, there are long-distance movements that result in migration permanently away from the site at which the movement began (dispersal).

Home ranges The size of home range that is exhibited by a species varies according to the habitat and food resources. Some species have small home ranges. For example, species occurring in rainforests or moist gullies in eucalypt forests, such as the Cape York rat, bush rat and mosaic-tailed rats, tend to have home ranges of less than half a hectare with small territories due to the availability of abundant local food. In the case of the mosaic-tailed rats, foraging occurs both on the ground and in trees with the vertical dimension greatly increasing the space available. The large rock-rats, which live in more open areas in northern Australia, have small home ranges centred around relatively productive vine thickets with nest sites occurring in rocky outcrops. At the other extreme, the home ranges of some of the native mice and rats in arid and semi-arid regions tend to be larger due to sparser resources, with tropical short-tailed mice and pebble-mound mice commonly maintaining home ranges of five hectares or more. When species exploit very dispersed resources, such as fruiting trees in the woodland of northern Australia, they may have to maintain very large home ranges, with the black-footed tree rat frequenting an area of 60 hectares or more. The size of a home range may also vary according to intraspecific competition although there is little detailed knowledge of aggression or territoriality for any species of native rodent in the natural environment. Nevertheless, laboratory studies on species such as the western chestnut mouse suggest that this is an important factor in determining the spacing of individuals.

Dispersal When dispersal takes place, much greater movements generally result. In the Northern Territory the dusky rat is forced to migrate each year as its dry season habitat becomes inundated by floodwaters during the summer monsoon. In other habitats dispersal is probably often associated with males searching for mates and, in eastern pebble-mound mice, males have been recorded moving between one to two kilometres in a

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single night. Food-driven dispersal may also be a powerful influence on individuals especially in populations of arid zone rodents. Sandy inland mice have been recorded moving 10 kilometres or more over the space of a few months. Rainfall and/or fire create patchiness of resources that promotes dispersal of these animals into areas of new plant growth. A similar dispersal has been proposed as the mechanism whereby heath mice colonise recently burnt areas of heath in western Victoria. The most extensive migration is performed by the long-haired rats in the arid zone which migrate hundreds of kilometres during a plague event and can move an average of three kilometres a day.

Population dynamics Rainfall and fire are important environmental cues that determine native rodent population dynamics because they affect food availability, which is probably the greatest single factor determining the ability of a site to support a population of a particular species, although vegetation structure and other factors may also be important. In southern Australia, where warm spring weather follows winter rains, and also in the north, where the summer monsoon determines when the abundance of food peaks, food resources generally change in an annual seasonal cycle. However, in the arid zone, rainfall is unpredictable and, under such conditions, the stability and persistence of populations is generally low, with occasional very high densities occurring.

Plagues Population cycles are a characteristic feature of small rodents, and species, such as voles and lemmings in the northern hemisphere, generally undergo a rapid population increase followed by a subsequent crash every three or so years. In the arid and semiarid regions of Australia several native mouse and rat species, as well as the house mouse, exhibit irruptions of populations, but these occur at much more variable intervals than those of voles and lemmings. Rainfall largely determines productivity, and hence food abundance, for the rodent species of the arid zone. When food is abundant, plagues can occur of long-haired rat, sandy inland mouse, spinifex hopping mouse, dusky hopping mouse as well as the house mouse and, to a lesser extent, the desert mouse and plains mouse. There tends to be a difference in the

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time lag between occurrence of rainfall and maximum abundance of these species due, in part, to their different reproductive potentials (see Chapter 5), with the introduced house mouse tending to become abundant sooner after rain than the native mice. The long-haired rat, like other arid zone rodents, is for much of the time an inconspicuous component of the community and is restricted to moist refuges of the Channel Country, Barkly Tableland and Ord River basin. However, when new vegetation and grass seeds become abundant following exceptionally high rainfall or floods, numbers of rats may increase dramatically and mass migration ensues. Irruptions of other native Rattus species, including the dusky rat in rice fields around Darwin, and the canefield rat in north-east Queensland cane fields, can also occur. The changes in population density of long- haired rats and dusky rats are the primary factors that determine the abundance of their respective main predators, the water python and letter- winged kite. The letter-winged kite is unusual among birds of prey in being semi-nocturnal, a habit that suits it well for exploiting nocturnally active prey such as long-haired rats.

Seasonal dynamics Reproductive activity is usually timed to produce young when resources are sufficiently abundant to give them a good chance of survival. Marked seasonal effects of cold winters in the south and summer rain in the north lead to relatively predictable seasonal breeding activity (Figure 7.1). In southern Australia, maximum population size generally occurs in summer and autumn following breeding in spring and summer. Most northern Australian species have been recorded breeding at all times of the year, but in rainforest species, such as the fawn-footed melomys and Cape York rat, reproductive activity increases at the beginning of the wet season, whereas in savannah and woodland species such as tree rats, rabbit rats, eastern pebble-mound mice and chestnut mice, maximal breeding generally takes place in the dry season following on from the monsoon. In areas with ‘predictable’ seasonal population cycles, there tends to be relatively little variation in population size from one year to the next, although differing environmental conditions, as well as population size in the preceding years, can result in some population density differences. However, in rainforest species such as the Cape York rat, giant white-tailed rat and Cape York melomys, populations are generally quite stable,

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exhibiting only small fluctuations between years unless there is a disturbance of habitat. In many forest mice and rats in south-eastern Australia, apparent complete disappearance of populations between years can occur. Indeed in the Hastings River mouse, New Holland mouse and smoky mouse, most populations are recorded for only short periods of time even when habitats have not obviously changed. This may be due to the fact that the populations of these species cannot undergo natural population cycles as a result of the direct or indirect impact of humans and high predation by introduced predators.

Fire Fire is critical in that it drives changes in populations of native flora and fauna. It results in immediate destruction of food and shelter afforded by vegetation, and thus tends to cause at least a temporary decrease in abundance of mice and rats at a particular site. Nevertheless, survival of these species during a fire is usually quite high due to shelter provided by their burrows, but after a fire has passed through an area, dispersal generally results. Trapping carried out immediately after fire often reveals

Wet

Early-mid dry season peak: Opportunistic (anytime of year): Brush-tailed rabbit rat, black-footed tree rat, Desert short-tailed mouse, greater stick-nest western chestnut mouse, common rock rat, rat, spinifex hopping mouse, dusky hopping eastern pebble-mound mouse, dusky rat, mouse, plains mouse, desert mouse, sandy canefield rat. inland mouse, long-haired rat, pale field rat. Dry S Wet

Wet season peak: Sp A Fawn-footed melomys, grassland melomys, giant white-tailed rat, water rat, Cape York rat.

W Dry

S S/Wet J Spring-summer season: D F Bush rat, swamp rat, silky mouse*, ash-grey N M mouse, smoky mouse, eastern chestnut mouse, Sp A Sp O A A Hastings River mouse, long-tailed mouse, New Holland mouse, broad-toothed rat, S M A J Mitchell’s hopping mouse, water rat. J * variable, some populations breed in winter W W/Dry

Figure 7.1 The main breeding periods for Australian rodents. Solid lines indicate peak breeding activity and births of young; arrows indicate that this period can be extended significantly at times of high resource abundance; broken lines indicate sporadic, low density, or unpredictable peaks in breeding.

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individuals moving through the area that were not present prior to the fire and that are not subsequently re-trapped in the same area, presumably due to lack of available food at that time. One exception to this is pebble- mound mice, which continue to inhabit burnt sites at the same population density before and after fires. In general, however, species rely on pockets of unburnt habitat as refuges, from which populations can subsequently expand. Such patches are probably vital for local recovery of many species, particularly those such as the bush rat that tends to disperse only short distances. After fire, as vegetation recovers, the early pioneering plant species, such as grasses, become prolific for a time. They are then replaced by slower-growing shrubs. Small-bodied species of native mice, such as the sandy inland mouse, New Holland mouse and delicate mouse, appear to be early succession specialists. Often these species reach their highest population densities one or two years after fire, following which time their populations decrease. In the eastern populations of the heath mouse abundance at recently burnt sites is greatest when plant diversity reaches its peak, then, after a couple of seasons, its population declines, partly due to dispersal to new sites, whereas in Western Australia, individuals appear to favour a later successional stage of recovering vegetation. In the silky mouse, the length of the breeding period appears to change at different times after fire, from being throughout the year in highly productive habitats to seasonal reproduction two to three years after fire. Other species become more abundant in later post-fire successional stages of vegetation. For instance, the smoky mouse seems to favour vegetation that is rich in heaths and legumes. In the forest understoreys and heaths in which it lives, the optimum vegetation structure occurs 10 or more years after fire. There is also considerable debate over the age of vegetation that best suits species such as the Hastings River mouse. Many native rodents probably have the capacity to survive in a variety of vegetation types in which they do not normally occur. Not only the diversity of vegetation and nature of food resources, but also the physical structure and density of vegetation, appear to be important in determining their suitability for a species. For instance, eastern chestnut mice and desert mice tend to inhabit vegetation that remains dominated by their food species such as grasses and sedges, but only move into an area once the vegetation has reached a medium density – a stage of recovery that may take only six months after a fire in North

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Queensland savannahs, but much longer on the central coast of New South Wales. Swamp rats and bush rats appear to prefer even denser vegetation and, although bush rat population density peaks in the years following fire, the species persists in all stages of vegetation.

Community structure Communities are collections of interacting individuals living in the same location. Animals within a community interact both with their environment and with each other. The composition of a community and its stability are therefore dependent upon processes that determine population size and habitat occupancy of the individual species, as well as upon the nature of competition that occurs between species present in a region (see Chapter 3). Other mammal species such as potoroos and bandicoots may compete with the native mice and rats for foods such as fungi and insects. Also important are animals that are likely to prey on rodents, such as quolls and Antechinus, as well as introduced species (see Chapter 10). If two similar species inhabit the same area, interspecific competition is likely to result in elimination of one or other of the species over time. Mechanisms that allow species to co-exist, therefore, involve differences between the species themselves, such as different diets or feeding behaviour, fine-scale spatial partitioning of habitats, or dynamic processes relating to changes in the suitability of habitat for different species following disturbance. There are many instances where species of Australian native mice and rats occurring at the same site differ in ways that reduce interspecific competition. For example, in northern Australia, the western chestnut mouse is much larger and more herbivorous than the small, granivorous, delicate mouse, and hence these two species do not compete for food. Similarly, broad-toothed rats and bush rats coexist in the Snowy Mountains but exploit different food resources; and rock-rat species that live at the same site not only have marked differences in body size, but also have different diets and foraging strategies. The outcomes of competition are generally spatial partitioning of habitat, or modification of the behaviour or ecology of one or other of the species involved. For example, the swamp rat is a specialist herbivore and will generally out-compete the more omnivorous bush rat with the result that the bush rat has to eat different foods to remain in the same habitat.

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However, away from sedgy swamps, the bush rat will tend to exclude the swamp rat. Interestingly, in Tasmania and the Grampians in Victoria, where the bush rat does not occur, the swamp rat is found in many habitats typically occupied by the bush rat in other parts of the continent. Where the swamp rat and the bush rat are present in a habitat and both become infected with a lungworm, the bush rat is likely to predominate because the parasite is less pathogenic in bush rats than in swamp rats (see Chapter 9). Rainforest communities exhibit another type of spatial partitioning of habitats. The prehensile-tailed rat forages high in the canopy, native Rattus generally on, or within, a few metres of the ground, and climbing (scansorial) white-tailed rats and melomys forage widely on the ground, throughout the mid-stratum and into the canopy. The species that occur in a given community may also change over time, since populations of individual species fluctuate in response to changes in food availability and other resources. The classical model for documenting changes in a community is to follow changes that occur after a major disturbance such as fire (Figure 7.2). Given that different mouse and rat species are favoured by different post-fire successional stages, it is not surprising that changes in community structure take place as vegetation recovers from fire. Many smaller species of native rodents are early-successional specialists, although the house mouse is one of the first species of rodent to appear in disturbed areas. However, often after a few months, densities of small native species begin to increase and may even displace the house mouse. For instance, on the central coast of New South Wales, the New Holland mouse has been shown to be competitively dominant over the house mouse, and this may also be the case for other native species in natural habitats. During early successional stages the densities of members of the delicate mouse group (e.g. delicate mouse, sandy inland or New Holland mouse) can become very high (exceeding 15 animals per hectare) and previously small populations may increase markedly. The appearance of larger species in the system such as chestnut mice, melomys and native Rattus, usually takes place at a time when a fall in population density of small-bodied species occurs probably largely due to a reduction in suitability of habitat. The rate of development of denser understorey influences the time at which the larger species re-invade. This can vary dramatically between events at the same site, as has been found on the

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New South Wales central coast, where a succession of mouse and rat species involving house mice, New Holland mice, eastern chestnut mice and swamp rats, that had previously taken years, occurred over a period of just months. The replacement of chestnut mice by competitively dominant swamp rats in older, denser vegetation, is partially tempered during spring and summer by the fact that these species can exploit different diets at this time. However, during autumn and winter, direct competition appears to occur with chestnut mice vacating the preferred vegetation of swamp rats. Compared to southern Australian sites, recovery of grass-dominated understoreys in tropical Australia often occurs quickly. Here a generalised succession of terrestrial rodent communities from delicate mice to chestnut mice, pale field rats and melomys may take place within the space of successive wet seasons. Other species, such as short-tailed mice, rock-rats and pebble-mound mice, are less predictable in their occurrence based on a disturbance regime, and seem to differ sufficiently from the above species such that they can coexist with any of them, while species such as tree rats

Figure 7.2 Simple model of post-fire recovery of an Australian rodent community. The pattern of recovery shown here is a general summary, but the outcomes of a fire event or other disturbance on rodent populations vary widely between events and sites.

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may require development of slower-growing shrubs for food and shelter, and will therefore generally only be found in older vegetation. The presence of a rodent species at any site is therefore the result of a number of factors. The ability of many Australian mice and rats to invade new sites in natural landscapes is quite high, as they are generally able to disperse long distances. The suitability of a site depends on a number of factors, including what other species are present and how long it has been since a fire or significant rainfall. Once established at a site, many mice and rats will undergo seasonal population fluctuations reflecting the changes in food resources, but disappear once the vegetation changes in response to successional replacement of the original type. Others, particularly in the arid zone, will rapidly peak in numbers, then become very scarce, or even disappear from the site. However, within any given region there are a wide variety of ecologies possessed by the different species and some, such as the bush rat, can continually inhabit a wide variety of vegetation types, while many other species will respond differently to the same sort of disturbance each time it occurs.

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ammals vary greatly in the level of complexity of their social Morganisation. Some species live solitary lives and exhibit a dispersed social organisation, except when they come together for mating and the rearing of young. Others live in various kinds of communal groups, the basic elements of which include attracting behaviour between group members and the potential for individual members to perform different roles or cooperate with each other. These differences in social organisation tend to influence the breeding system, with those living a solitary existence often being monogamous, while in communal species, polygamy or promiscuity is more likely to occur. The various types of social organisation that occur in rodents in North America, Europe and southern Africa have been well studied. Beavers, for example, live as small family units where both parents care for, and rear, the young within the family territory. Other rather different rodents such as Syrian hamsters also have a dispersed social organisation with the territory of a pair being defended against intruders. Prairie voles, which occur in the grasslands of central North America, live as monogamous pairs and generally have non-overlapping home ranges.

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At the other extreme, very large groupings of individuals may occur. For instance, large ‘towns’ exist where up to several hundred prairie dogs may live together at the same location. However, the most extreme form of mammalian sociality is exhibited by two species of African rodent – the naked mole rat of East Africa and the Damaraland mole rat of Namibia. Groups of these mole rats live in subterranean burrows where there is a single breeding female and up to three sperm-producing males in each group. Similar to some insect and bird societies, other non-reproductive females are also present that assist in the maintenance and defence of the nest site and with raising the young born to the single female, or ‘queen’. Interestingly, the details of the social systems differ between these two species with the naked mole rat living in larger groups and having a dominant female, whereas in the Damaraland mole rat, the male is the dominant member of the group. The question thus arises: why has such a wide variety of social organisations evolved? Research into mammalian social organisation often focuses on perceived costs and benefits of communal living. Costs of group living include increased competition for resources, greater risk of becoming infected with diseases or parasites, and higher chances of disturb ance in the production of young, including infanticide. By contrast the benefits of group living, particularly in cold or arid environments, include conservation of energy due to huddling, increased burrow humidity, better protection from predators due to group defence and coopera tion between group members in food gathering, nest site or burrow construc tion. Group living can lead to communal breeding, where members of a group reproduce at the same time and, in this situation, individual group members may assist in the raising of each other’s young. Communal living is likely to evolve if potential benefits outweigh costs, whereas if that is not the case then a dispersed organisation may be expected to occur. In a few species, a flexible system is present, with the type of social organisation exhibited by a population varying in response to changes in environmental conditions and/or to different habitats in which the species is present. Given that Australian native mice and rats occur in a variety of different environments, can we see any differences in patterns of social behaviour among the various groups? In contrast to the many studies on rodents occurring on other continents, there has been comparatively little research on the social organisation of Australian rodents with much of our

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knowledge coming from observations obtained while carrying out ecological research or on museum collecting expeditions.

Social organisation under captive conditions Behavioural research on native rodents housed in captivity has revealed significant differences among the different species. These include differences in attracting and amicable behaviour such as huddling and sniffing, as well as in repelling behaviour such as skirmishes and aggressive interactions. Early observations carried out in the 1940s on the northern hopping mouse showed that individuals of this species were ‘… strongly gregarious and all the animals put together in a cage are found in a great heap. They do not appear to fight or to be in the least aggressive …’. Such observations are consistent with this species exhibiting some form of communal social organisation, though agonistic interactions were found to occur when strangers were first placed together. Similar observations have been made on the spinifex hopping mouse. When two adult males were placed together there was initially a little fighting but, after a short time, attracting behaviour developed between the individuals with the consequence that, within a day or two, they cohabited the same nest. Similar experiments were carried out with females which showed that, although there were initially higher levels of repelling behaviour than between the males, again elements of agonistic behaviour rapidly diminished with the result that after a day or two they also shared the same nest. In general it has been found that in hopping mice, members of the same group exhibit much huddling behaviour (see Fig. 8.1) and mutual grooming such that all members of the same group recognise each other. Introduction of a stranger, who is not a member of the same group, is immediately identified with the result that group members, and in particular the females, will expel the stranger. Subsequent observations have shown that when groups of hopping mice are kept together at room temperature, metabolic rate, oxygen consumption and evaporative water loss of individuals within the group are all significantly reduced. At temperatures above about 30°C, group members modify their behaviour such that they lie apart from each other with limbs outstretched, presumably to maximise evaporative cooling. Behavioural studies of silky mice have shown that, as in hopping mice, initial repelling behaviour takes place between strangers but, after a while,

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Figure 8.1 A group of spinifex hopping mice in captivity, huddling together

attracting behaviour develops. However, unlike in hopping mice, males tend to be more aggressive than females. This has also been found to be the case in groups of plains mice where the males appear to develop a dominance social hierarchy with some of the subordinate individuals becoming reproductively suppressed. Individual plains mice also exhibit a characteristic behaviour whereby group members stand up on their back legs (Figure 8.2) and spar at each other with their forelimbs, whilst at the same time emitting loud, defensive vocalisations at the intruders. In spite of this hostile behaviour, adult members of the same group will live amicably together for prolonged periods of time with olfactory communication probably taking place between the cohabiting individuals (Figure 8.3). In other species of native mice, behavioural interactions appear to be very different. For instance, in heath mice, when two strange males or females are placed together, they remain aggressive towards each other for prolonged periods of time and tend not to end up sharing the same nest. This suggests that individuals of this species may generally be intolerant of each other. However, when larger groups of male and female heath mice are placed in linked enclosures that provide avenues to avoid

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Figure 8.2 Adult plains mouse Figure 8.3 Young and adult plains mice showing the typical posture adopted inspecting each other, suggesting olfactory when sparring. cues are used for individual recognition.

each other, pair bonding between the largest male and female mice seems to occur, and subordinate males will nest together. Not only is pair bonding potentially important, but the opportunity to choose a mate may be necessary for the success of captive breeding. Pair bonding also seemed to be an important component of captive breeding in a trial that examined broad-toothed rats, with couples need ing to be introduced to each other in large outdoor enclosures for extended periods before breeding occurred. The most aggressive behaviour noted among Australian rodents was exhibited by western chestnut mice and desert mice. With these species there are invariably high levels of inter- male aggression when two strangers are placed together, with no huddling or cohabitation behaviour developing over time. Such observations clearly indicate some form of dispersed, rather than com munal, social organisation in these species.

Social organisation in the natural environment Hopping mice Spinifex hopping mice are a characteristic species of stabilised sand dunes of the arid interior of the continent. They live predominantly in deep burrows which they construct by digging with their front feet and kicking the sand behind them with their hind feet (Figure 8.4). One or more horizontal tunnels containing a nest chamber lined with dry grass

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Figure 8.4 Long hind feet of spinifex hopping mouse are used for hopping and kicking sand, thus facilitating burrow construction.

Figure 8.5 Pop holes (arrows) created by spinifex hopping mice pass vertically up to the surface from an underground tunnel usually located about a metre beneath the surface within which one or more nests occur. Inset: A spinifex hopping mouse pophole.

and leaves are made. From these horizontal tunnels vertical shafts lead to the surface (Figure 8.5) with the nest chambers being up to a metre beneath the surface. Here a more-or-less constant environment of relatively high humidity occurs in which there is far less temperature fluctuation than outside the burrows on the surface of the sand. Clearly, to form such complex tunnel systems, group behaviour between several individuals

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would be an advantage. However, evidence for group composition in the natural environment is very limited. Early observations of several burrow systems of spinifex hopping mice suggested up to three males and four females lived together with young in the one burrow. However, there appears to be little further information on group composition in the wild although social organisation appears to vary over time as a result of altered environmental conditions. During dry conditions the animals may generally live singly or in small groups of at most two or three, whereas after high rainfall and the associated increase in food availability, individuals may be sedentary, with groups living together in the same burrow. Three other species of hopping mice – the dusky hopping mouse, the northern hopping mouse and Mitchell’s hopping mouse – live in sand dunes. They create similar complex deep burrow systems, which act as a place of refuge and nest site for young, and from which vertical shafts pass to the surface. Up to five dusky hopping mice have been found in the one burrow and there is one report of eight Mitchell’s hopping mice occurring together within one burrow complex, although no details of reproductive status of these groups were recorded and one to four animals per burrow appears to be more common.

Native mice in the genus Pseudomys Silky mice and ash-grey mice are two closely related species that both occur in sandy habitats and, like hopping mice, both excavate deep burrows. The animals initially dig a shaft, at about 45° to the surface, and this extends to a system of horizontal tunnels, together with a nest chamber, with vertical shafts ascending to the surface. Up to several litters of silky mice have been found in the same burrow, and adult males have been found to range widely with more than one breeding male sometimes occurring in a particular burrow system. However, the social organisation of silky mice appears to be flexible, as small family groups as well as larger social aggregations all occur during breeding. Plains mice have occasionally been found to occur in large colonies. A radio-tracking study carried out during years when population density was low showed that these animals either live in cracks in drainage depressions, where they make cup-shaped nests up to 50 cm beneath the surface, or in shallow burrows among roots of perennial shrubs. However their social behaviour appears to vary in relation to habitat productivity such that, during favourable conditions, sedentary behaviour occurs with

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males having overlapping home ranges. When food supply is limited, animals may be nomadic with males travelling more widely than females. The sandy inland mouse which, as its name suggests, tends to occur in sandy habitats of the arid zone, has been found in aggregations of up to 22 individuals within the one burrow system, although these animals were not in breeding condition at this time. However, during times of repro duc- tive activity no more than one family group has been recorded together, suggesting that this species changes its social organisation depending upon whether or not reproduction is taking place. The desert mouse, which occurs both in the arid zone and in some semi-arid regions, appears to have a very different social organisation. Individuals have generally been found living alone or as single family groups in shallow burrows or even on the surface under dense vegetation. Among the native mice species occurring in the south-eastern heaths, radio-tracking data of heath mice has indicated that single adult males and females tend to associate with each other and that pair bonding may occur. In Tasmania, long-tailed mice have also usually been found in underground nests as a single pair together with young. Females occur in more or less exclusive home ranges with those of males overlapping two, or occasionally more, home ranges of females. In the smoky mouse, by contrast, there is evidence of communal nesting. These animals excavate extensive burrow systems with multiple nest chambers and up to five breeding females and a male have been found in a single burrow.

Broad-toothed rats The social organisation of the broad-toothed rat differs between summer and winter. During the summer breeding season adults do not cohabit, with females having overlapping home ranges and males having larger home ranges that encompass those of several females. During winter, when the ground is covered with snow, home ranges decrease in size and both males and females huddle together in communal nests, presumably for warmth. With the arrival of spring, males become nomadic and may be found in suboptimal habitat, suggesting that dispersal of females determines the social structure and spatial organisation of this species.

Short-tailed mice A radio-telemetry study of the tropical short-tailed mice on Thevenard Island, 20 km off the north-west coast of Western Australia, found that,

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in contrast to the house mice that live in the same area, these animals are nomadic and shelter during the day in simple burrows up to about 50 cm below the surface. Only one animal was ever found in a burrow at any one time and individuals often shifted from one burrow to another on successive nights, suggesting that this species has a dispersed social organisation. The desert short-tailed mouse also appears to live a solitary, nomadic existence sheltering during the day in shallow burrows or deep soil cracks containing a single nest chamber.

Tree rats and mosaic-tailed rats Little is known about the social behaviour of these species. Both the black-footed tree rat and the golden-backed tree rat, as well as the giant white-tailed rat, generally nest in tree hollows, although tree rats can also be found in the roofs of houses. All three species occur at low densities with the only social groupings appearing to be mother with young. Radio- tracking studies have shown that individuals travel large distances during the night when foraging for food and, in the case of the giant white-tailed rat at least, overlapping home ranges occur. A dispersed social organisation is thus suggested. Like the giant white-tailed rat, the fawn-footed melomys occurs in rainforest but, rather than living in tree hollows, it usually makes its nest of pandanus leaves, banana leaves or grass up to two metres above the ground in trees or shrubs. The male fawn-footed melomys has an exclusive home range which he defends against intruders. The grassland melomys constructs a large spherical nest from grass or leaves up to 50 cm in diameter, within which the female will have her young. Due to their aggressiveness towards each other in the laboratory, it has been concluded that melomys, like white-tailed rats and tree rats, probably exhibit a dispersed social organisation.

Native Rattus The bush rat, which is a characteristic species of eucalypt woodland throughout much of the southern and eastern parts of the country, appears to have a social organisation that varies depending on habitat and/or season. In a population of bush rats studied in Sherbrooke Forest in Victoria, overlapping home ranges were found to occur in the non- breeding season but during the breeding season there was little overlap between females, although males ranged widely. It thus appears that, at

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least during the breeding season, females are territorial and sedentary, with males exhibiting greater mobility. Studies carried out on island bush rat populations have, however, suggested that animals may show more tolerance of strangers than those in the mainland populations. The swamp rat, which is the other species of native Rattus that is common in south- eastern Australia, differs from the bush rat in forming extensive runways amongst sedges and tall grasses. In spring, females defend a territory, whereas males have larger home ranges. In these animals the incidence of tail scarring, indicative of fighting, suggests significantly higher levels of intermale conflict during the breeding season than at other times. Of the grassland species of native Rattus, the canefield rat, which occurs in north Queensland, makes extensive burrows and tunnels of 5 to 10 cm in diameter in which there are nests of dry grass. Unlike bush and swamp rats, canefield rats appear to live communally. Very dense populations can occur, with up to 23 non-breeding animals having been found in a single nest chamber. An even more extreme situation may be present in the long-haired rat. During plagues of this species, two types of burrow system have been found – one, a simple tunnel with two entrances and the other a network of burrows with many entrances within which there is a single nest. Unfortunately the number of animals occupying these warrens is not known as the burrows were uninhabited at the time of excavation. Not much is known about the social organisation of these interesting animals, either during times of high population density or during periods when the animals in much of their range are restricted to their refuge areas around swamps and soaks.

Specialised home bases Pebble mounds Pebble-mound mice construct mounds of pebbles around the entrances of their burrow systems (Figure 8.6). These animals carry pebbles in their mouths and use their forelimbs to shuffle the stones into position. Mounds can measure over three metres in length and cover more than ten square metres. Individual pebble ramparts around burrow entrances can measure 50 cm in diameter and be up to 25 cm in height. Some mounds have probably lasted for centuries, and been re-used by generation after generation of mice. The primary function of these mounds may be one of defence against predators. Mounds are the centre of activity for the

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Figure 8.6 A mound constructed by pebble-mound mice.

two species that have been studied, but the number of mice living in the mounds seems to differ between the species. Very large social groups of up to 14 individuals of different ages have been recorded in mounds of the western pebble-mound mouse, while the eastern pebble-mound mouse seems to be much less social. Females of all species appear to visit and manipulate pebbles at multiple mounds, but why this should be the case is unclear.

Stick nests The greater stick-nest rat builds large nests of interwoven sticks (Figure 8.7) that are occupied by successive generations of individuals. On Franklin Island in the Great Australian Bight, the only location where these animals have naturally survived, stick nests are typically located in thick bushes, caves or overhangs in limestone cliffs. Nests of this species vary greatly in their complexity. They are built with sticks, stones and various other items and include a chamber lined with bark and small sticks from which tunnels radiate, with burrows sometimes being excavated beneath the nest. Several early European explorers came across these animals on the mainland of southern Australia and they speculated that these stick nests protected the animals from extremes of climate as well as from predators, although a brown hawk has been recorded nesting on the top of a large

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Figure 8.7 Nest of stick-nest rats on Salutation Island.

stick nest near Ooldea on the Nullarbor Plain! Radio-tracking data have shown that adult females have well-defined home ranges with small core areas, and that adult males have considerably larger home ranges but less well-defined core areas.

Peat mounds The water mouse is a highly specialised terrestrial carnivorous native rodent that lives along the littoral zone and in mangrove swamps in Queensland and the Northern Territory. A study of the water mouse on North Stradbroke Island found that animals lived either in nest mounds or in tunnels constructed in banks just above the high tide level. The mounds were of peat, sedge, mud and sand, and were up to 60 cm in height and 48 cm in circumference. They had several entrances and an extensive tunnel system within which there were nest chambers lined with dried melaleuca leaves. Although the lower holes were flooded at high tide, the mounds did not become totally inundated, with the nesting chambers being near the top of the mound. Up to eight individuals have been found in each group, with only one adult male being present at any one time. As the tide receded, animals emerged from these mounds to forage among the roots of mangroves often following the receding tide. Although home ranges overlapped, it was found that the core areas of males did not, thus it was presumed that there was territorial male defence.

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Greater stick-nest rats and their nest. Drawing by Ella Fry.

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In conclusion, it is evident that, although we only have a rather fragmentary knowledge of the social behaviour of the Australian rodents, a range of social organisations occurs amongst both the Old Endemic groups and the native Rattus, which probably varies from dispersed to communal organisation in both groups. In the Old Endemics, communal social organisation tends to occur in species that live in the arid and semiarid regions of the country although the desert mouse seems to have a dispersed social organisation. In more seasonal and tropical environments most species tend to live as isolated pairs and thus have a dispersed social organisation, although the smoky mouse appears to be an exception to this with some evidence that these animals can live communally. A few species construct specialised home bases such as pebble mounds or stick nests that are used by successive generations of animals. Despite our limited knowledge of the social organisation of Australian rodents, we still know virtually nothing about the breeding systems of most of the species in the natural environment. Future studies need to focus on distinguishing between the nesting and breeding behaviour of those species in the more arid areas that do not have clearly defined breeding seasons and that are likely to exhibit flexible social nesting behaviour relative to their breeding activity.

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he effects of parasites and disease on animal populations have, in Tthe past, often been overlooked. However, in recent times, it has become evident that parasites (including bacteria and viruses) can have a major impact on wildlife populations. ‘Extinction by infection’ is a very real phenomenon, particularly in animal populations that have become reduced in size and/or range due to human activity. Increased transportation of animals and animal products around the world has resulted in more frequent opportunities for pathogens to be introduced to new animal populations and hence to invade new animal hosts, sometimes with devastating effects on naïve populations. The effect that a particular parasite may have on a population of rodents will vary depending on the effects of the parasite on the individual, together with the host’s behaviour and abundance. A parasite in a rodent population may reduce the size of that population by increasing mortality, it may limit population growth by reducing fitness and reproduction, or it may be carried in a population with little, if any, effect on the health of the individuals or the dynamics of the population.

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Parasites of native rodent species may also spread to other native animals, domestic species, or even humans. Most native mice and rats have co-evolved over thousands of years with the parasites that they host. This often leads to a species-specific relationship between the parasite and its host which is finely balanced between the parasite’s elimination by the host’s immune response on the one hand, and death of the host due to disease caused by the parasite on the other. Such a delicate balance between host and parasite may be upset when host populations are under pressure from habitat destruction, hyper- predation, or competition from introduced species. The effects of disease are often greater when rodents are held in captivity due to high stocking density, altered environmental conditions and small population size. To fully under stand the biology and ecology of Australia’s rodents as well as to effectively manage their conservation, some knowledge of the organisms that live in and on them is required.

Helminths: cestodes (tapeworms), nematodes (roundworms) and trematodes (flatworms) Helminths have been recorded from all major groups of native Australian rodents; the Old Endemics, the native Rattus and also the introduced species. The ancestors of each lineage of rodents undoubtedly entered Australia with their own suite of parasites, some of which have since moved between different rodent lineages and also, in some cases, to marsupial species that share the same environment. The species of helminths carried by a particular rodent species may suggest the geographical origin of the species concerned. The finding of similar species of nematodes in both the Old Endemics and native Rattus as well as in rodent species occurring in Indonesia, suggests South-East Asian ancestry of both the rodents and their parasites. For instance, the nematode Cyclodonostomum purvisi which occurs in the canefield rat in Australia is also found in several native Rattus and bandicoot rat species in Indonesia and Malaysia. Likewise the nematode Tikusnema vandycki, which occurs in the water mouse is also found in some species of Indonesian rats. The water rat hosts nematode species found in dasyurid marsupials, suggesting transfer of these species of parasites from marsupials to the water rat after its arrival in Australia.

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While most species of native rodents host mainly nematodes as in most other terrestrial rodents, the water rat, by contrast, hosts predominantly trematodes. These flatworms require an aquatic mollusc as a first intermediate host and hence they are usually found in animals living in or near water. These parasites then move to a second intermediate host which may be an insect, crustacean, fish or amphibian. Finally the parasite can complete its life cycle if the second intermediate host is eaten by a water rat. The water rat’s aquatic lifestyle, together with its varied diet, makes it particularly susceptible to infection by this type of parasite, with over 30 species of trematodes having been recorded from water rats to date. The helminth community in the water rat shows significant geographical variation. Different helminth species occur in north Queensland, central and southern Queensland, southern mainland Australia and Tasmania. Few species of helminth are found across multiple regions and there is a much greater similarity of helminth species found within each region than between them. These regional differences in the helminth community in water rats are likely to be due to ecological factors influencing the abundance and distribution of their intermediate hosts with invertebrate, amphibian and fish species varying considerably between different geographic regions in which the water rats are present. Various host-swapping events have occurred involving Australian rodents where a parasite has transferred from its usual host to an unrelated host in the same environ ment. This is believed to be an important process driving parasite evolution. There is some evidence that helminths have moved from marsupials to Australian rodents and then evolved into new species unique to their rodent hosts. For example, members of the nematode genus Woolleya are generally found only in marsupials, although one species, W. hydromyos, occurs in Old Endemic rodents. Sim ilarly, nematodes of the genus Paraustrongylus generally occur only in marsupials, apart from P. ratti, which occurs in the native Rattus. Such findings are consistent with the more recent arrival of rats and mice in Australia compared with marsupials and their subsequent infection with parasites that originally evolved in the marsupial fauna. Helminths found in more than one rodent species may not affect each species in the same way. For instance, the lungworm, Gallegostrongylus australis, is found in the lungs of the bush rat where it generally causes

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only mild pathological changes, whereas in the swamp rat this parasite can be responsible for debilitating lung damage. These findings suggest that the lungworm originally evolved in the bush rat and that this species coevolved with it such that the parasite does not have a devastating effect on the host. However, as this same parasite causes significant disease in swamp rats, it is possible that this latter species has been more recently infected by the parasite and has had less time to co-evolve a balanced host- parasite relationship. An ecological consequence of this is that the parasite may give the bush rat a competitive advantage over the swamp rat when both species occur in the same habitat and both become infected.

Ectoparasites: ticks, mites and fleas External parasites, such as ticks, mites and fleas, have been found on many species of Australian native rodents. These ectoparasites themselves have not been shown to cause disease under natural conditions but they can act as agents for transmitting pathogens between individual animals. For example, fleas may transmit disease-causing bacteria between rodents. Some Australian rodents host a diverse range of ectoparasites, with 22 species of fleas from 11 genera and seven families recorded from bush rats alone. A large number of mite species have also been found living on native rodents. Most inhabit the skin, but they have also been found in the nasal passages of several Australian rodent species as well as in the oral cavity of spinifex hopping mice. Mites are important in their potential for carrying the rickettsia Orientia tsutsugamushi, which causes scrub typhus in humans. The mite, Lepto- trombidium deliense, is the vector for scrub typhus with the main rodent hosts in Australia probably being the fawn-footed melomys, giant white- tailed rat and bush rat. Humans bitten by mites carrying the rickettsial bacterium can develop a rash, pneumonia and potentially fatal encephalitis if the disease is not diagnosed and treated. The rickettsia O. tsutsugamushi is passed from adult mites to their offspring by transovarial transmission, which means that infection is maintained by an infected female mite laying eggs infected with the bacterium. Scrub typhus is known to occur in parts of north-eastern Australia including Cape York and has also been reported from the Northern Territory and Western Australia.

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Protozoa Protozoa are single-cell organisms capable of infecting a range of body tissues including muscle, brain and blood. They may have a one-host life cycle and are transmitted directly between hosts of the same species, or they may require more than one host species to complete their life cycle, e.g. Sarcocystis. The parasite Toxoplasma gondii is a widespread protozoan parasite that needs to infect a cat to complete its life cycle but can also infect many other mammal species including humans. It probably arrived with the first cats to reach Australia, about 250 years ago, and hence is a relatively new parasite for Australian rodents to contend with. Toxoplasma cysts have been found in the muscle tissue of many rodent species without causing any apparent ill effects. However, these cysts have been shown to cause inflammation of the brain in the water rat. Also, Toxoplasma infection of brown rats has been shown to alter their behaviour, whereby they lose their instinctive avoidance of cats, thus increasing their chances of being preyed upon and hence allowing the parasite to complete its life cycle. Whether such effects occur in native Australian rodents is not known. Sarcocystis species are protozoa that have a two-host life cycle. These parasites require a definitive host, usually a carnivore, in which sexual reproduction of the parasite occurs and an intermediate host, usually a herbivore, in which asexual reproduction takes place. The bush rat, swamp rat, canefield rat, giant white-tailed rat, fawn-footed melomys, long-tailed mouse and water rat are all known to be intermediate hosts for Sarcocystis. In south-eastern Australia and Tasmania, tiger snakes (Notechis sp.) appear to be the definitive host for Sarcocystis murinotechis and they become infected after eating a rodent carrying the parasite (see Figure 9.1). Mice and rats become inadvertently infected by ingesting sporocysts shed in snake faeces that remain infective in the soil for some time. Studies suggest that other predators of rodents in south-eastern Australia, such as cats, owls and quolls (Dasyurus virerrinus), are not involved in the Sarcocystis murinotechis life cycle. A different Sarcocystis species occurs in tropical and subtropical Australia that has a life cycle that involves bush rats and carpet pythons (Morelia spilota). Infection rates in wild-caught bush rats are often high, with up to 95% of individuals being infected in some areas. Bush rats and carpet pythons are also the hosts required for the nematode Amplicaecum robertsi to complete its life cycle. A study in Queensland has

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bush rat Sarcocystis

swamp rat

Sarcocystis

Figure 9.1 Life cycle of Sarcocystis species showing the involvement of carpet pythons in north-eastern Australia and tiger snakes in south-eastern Australia. Parasite sporocysts are shed in snake faeces and infect the soil. Mice and rats then become infected when they ingest a sporocyst which multiplies in the muscle tissue. The parasite completes its life cycle when the rodent is then eaten by a snake.

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shown more than 50% of wild caught bush rats were simultaneously infected with both A. robertsi and Sarcocystis sp., which clearly illustrates a close ecological relationship between predator, prey and parasite. Maclear’s rat was a semi-arboreal rodent endemic to Christmas Island (an Australian Dependency located south of Java). This native rat species was abundant until the late 1800s but became extinct in the early 1900s, possibly due to a blood-borne protozoan parasite. In 1899 the black rat was introduced to the island and notes from the diary of Herbert Durham (a pathologist who visited Christmas Island in 1901 to 1902) indicated a species of trypanosome, a blood-borne protozoan, was present in black rats, as well as in Maclear’s rats that occurred near the main settlement. However, Maclear’s rats living away from the settlement were free of trypanosomes. In 1903 many sick and dying Maclear’s rats were seen on the island and by 1908 Maclear’s rat had become extinct. It is likely that the black rats brought the trypanosome to Christmas Island. With no previous exposure to this parasite, the native Maclear’s rats probably had no immunity and were vulnerable to severe disease and extinction.

Bacteria Bacteria, such as Salmonella and Leptospira, have been shown to be carried by Australian rodents but they are not reported to cause any significant disease in their natural hosts. Rodents can, however, act as a resevior for bacteria and are capable of transferring them to domestic animals or humans. In 1986 a case of leptospirosis was reported in a zoologist who had almost certainly contracted the disease whilst handling wild bush rats. The leptospire bacteria were probably present in the rat’s urine and entered the individual’s bloodstream when rat urine came into contact with bite wounds, or scratches, on his hands sustained while handling the rats. Bacteria frequently infect the skin and underlying tissues following bite wounds from conspecifics and predators. The bacterium Streptobacillus moniliformis causes the disease rat-bite fever in humans and has been recorded in captive spinifex hopping mice and wild house mice in Australia. It may be a normal inhabitant of the nasopharynx of wild house mice and brown rats and only cause disease at times of reduced immunity due to stress, for example when population densities are very high during mouse plagues.

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The bacterium Yersinia pestis is carried by various Asian and North American rodents, without causing disease symptoms, and is transmitted between individuals by fleas. In other species of mammals, including humans, it causes bubonic plague, a disease that has been responsible for millions of human deaths around the world including the historical episode known as the Black Death. Plague occurred briefly in Australia in the early 20th century, resulting in the deaths of over 500 people in several major cities including Sydney, Brisbane and Melbourne. It almost certainly entered Australia with infected black rats carried by ships from ports in Asia. However, plague is often fatal for black rats and therefore this species is unlikely to be the primary reservoir for the bacteria. Although the bacterium is no longer believed to be present in Australia, it is endemic in several regions of the world including Central Asia, parts of South-East Asia and North America.

Viruses Little is known of the range of viruses infecting Australian rodents and even less about the effects they have on individual animals and their populations. Antibodies to a number of viruses have been found in house mice in Australia. These include murine cytomegalovirus (MCMV), murine hepatitis virus, murine rotavirus, mouse adenovirus, mouse parvovirus, lymphocytic choriomeningitis virus and Sendai virus. The limited studies so far performed have not found these viruses to be present in any native rodent species. It has been suggested that the introduction of house mice with their various viruses to Australia may have given them a competitive advantage over the native species which were likely to be naïve to these viruses. MCMV has been of interest as a potential biological control agent for house mice. Since house mouse plagues are responsible for significant economic loss and damage in the agricultural industry in Australia, there is much interest in controlling house mouse numbers by reducing their fertility using immunocontraception. Fertility control of wild house mice could be carried out by using a species-specific vector such as MCMV into which the gene for the sperm-binding egg-coat (zona pellucida) protein has been artificially incorporated. MCMV causes no overt disease in house mice and is carried asymptomatically in many house mouse populations. When house

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mice become infected with genetically modified MCMV that incorporates the gene for the egg-coat protein, they raise an immune response to this protein, the sperm are blocked from binding to the egg coat (see Figure 5.6) and fertilisation is prevented. Fertility in the population is thus reduced which leads to a reduction in population size due to natural attrition over time. This could potentially provide a humane way of reducing house mouse populations. However, the release of a genetically modified viral vector for immunocontraception into the wild raises important environmental concerns, not the least of which is the species specificity of the virus and the similarity of egg coat glycoproteins across species. Because of these and other concerns, it seems unlikely that this approach will be used to control house mice populations in Australia in the near future. Two paramyxoviruses, Mossman virus and J virus, are apparently unique to rodents in Australia. Mossman virus has been found in Cape York rats and bush rats trapped in Queensland in the early 1970s. J Virus was found in wild house mice and brown rats, also in Queensland, where it appears to be a respiratory pathogen causing pneumonia. Neither virus has been fully characterised nor is their significance to wild populations known. It is likely that many other viruses exist in Australia’s native rodents. Hantaviruses, for example, have been found in many rodent species throughout the world outside Australia and are of public health significance as they can potentially cause fatal disease in humans. Given the range of rodent species known to occur in Australia and the fact that rodents arrived in this country on several separate occasions, various hantaviruses may well exist at least in some populations of native rodents.

Disease of rodents in captivity Australian rodents held in captivity suffer from a range of diseases, most of which are due to being kept in less than ideal conditions. Overcrowding can lead to increased stress and aggression between individuals with bite wounds being a significant cause of mortality in captivity. Tyzzer’s disease, a bacterial infection caused by Clostridium piliformis, has been reported in spinifex hopping mice and is thought to be carried asymptomatically by some individuals but can be a significant cause of disease and death in stressed or weak animals. Most intestinal parasites do not appear to cause

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problems to native rodents in captivity if appropriate hygienic conditions are provided. Disease syndromes of possible genetic origin have been observed in captive greater stick-nest rats, but their cause has not been determined. Some individuals of this species have developed ocular cataracts and a glomerulonephropathy (kidney disease) has been found to be the primary cause of death in others. While parasites of Australian rodents can pose a significant threat to rare native rodent species and have potential to cause disease in humans, they can also provide useful information about their host’s biology. Parasites should be recognised as contributing to biodiversity and hence having conservation value in their own right. It is worth considering that for each rodent species that may become extinct, a number of species specific parasites may also become extinct at the same time, thus reducing global biodiversity by a number of species, not just one. Further study and greater understanding of Australia’s rodent parasites will allow the successful management of the threats they pose and maximise benefit from the stories they are able to tell about the ‘web of life’ in which they are an integral part.

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n Australia, like most other countries, the introduced house mouse and Ithe black rat are major pests. However, this is generally not the case for species of Australian native mice and rats, which tend to be absent from altered environments. Although the water rat lives along rivers and creeks in most of our cities and towns it has not become a pest. Only the canefield rat of Queensland and its close relatives, together with the grassland melomys, have had any major economic impact. Most Australian native mice and rats do not occur outside their natural habitats and even adaptable species, such as the bush rat, barely impinge on human habitation. Around 10 of the 70 or so species of native mice and rats that were present on the mainland when Europeans first colonised Australia around 220 years ago, are now extinct (Table 10.1). About 14 species are considered to be endangered at either a federal or state level and 15 are classified as nationally threatened with extinction, with many others having greatly reduced ranges. All the extinctions that have occurred have taken place in drier parts of southern and central Australia, and most of the species with greatly reduced ranges also occur in the southern part of the country. No species of native rodent, so far as is known, has become extinct in either northern Australia or Tasmania since the arrival of Europeans.

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Various factors, together with their combined effects, have been suggested as directly or indirectly having caused range contractions and extinctions of native rodents. These include:

• pastoralism and the associated changes in soils and vegetation • altered fire regimes from frequent small patch burning by Aboriginals to large-scale, hot, wild fires • competition with rabbits • predation by either introduced cats and/or foxes • drought. The cumulative effect of foxes and rabbits, in particular, is thought to have had a devastating effect on the Australian Old Endemics. High rabbit numbers not only lead to direct competition for food and degradation of habitat, but also enable high fox numbers to occur and thereby, indirectly increase predation pressure on other species such as the native mice and rats. Retrospective studies that attempt to determine causes of past population declines are by necessity speculative and rely on com parisons between inadequate knowledge of the distributions of species and patterns of declines. Efforts to conserve species need to focus on recovering species in the current environment. Some important gains have recently been made by aggres sively focussing on factors known to have an impact on native mice and rats, such as predation by foxes, regardless of whether these caused declines in the past. As well as significant government-funded projects, there are also pri vately-funded projects that are aimed at saving threatened and endangered species from extinction. Both federal and state legislations encompass various measures directed towards conservation programs although this was not the case in the past and much of the decline and extinction of Australian mice and rats occurred long before conservation of threatened species became a political issue. In 1925 the plight of native mice and rats was noted by Frederick Wood-Jones who stated: Let us remember that the protection of ‘native’ animals should not only apply to the marsupials, but that it ought to be extended to [the rodents, which are] … deserving of all the protection that legal enactments can give them … Many years of conscientious work will be needed to atone for the many past years of neglect.

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However, it was not until fairly recently that serious attention and resources were applied to the conservation of these species. Fortunately, there are now active conservation programs aimed at saving native mice and rats from extinction. Conserving species requires various strategies, including the promotion of a public profile of a species and/or the environment in which it occurs, lobbying government officials and landholders, and fundraising. Here we will briefly review aspects of research and implementation of management strategies that have been applied to conservation of the native mice and rats in different parts of the continent. We also outline various specific examples at the end of the chapter.

Research in conservation The first stage of formulating a conservation plan for a particular species is to determine its status, that is, whether the species is secure and hence in no need of assistance, whether it is potentially threatened by ongoing processes that may need to be controlled for its survival, or whether it is already endangered and hence in immediate need of assistance. There are several relevant lists of the status of Australian mice and rat species, and current listings by state and federal conservation agencies are presented in Table 10.1. Other lists include the IUCN (The World Conservation Union) Red List of Threatened Species, which includes species at risk of extinction. These lists are intended to be readily understood internationally and the status of native Australian mice and rats has recently been reviewed by the IUCN (see Table 10.3). Most criteria used to assess the status of species are based on a comparison of its present and past distribution, current and past population size, and the species’ susceptibility to threatening processes such as land clearing, predation, or inappropriate fire regimes. Rapid declines in population or distribution generally result in a species being listed as ‘threatened’, with sub-categories ranging from vulnerable to endangered. Thus listing of a particular species on government schedules is important as the status results in legal obligations for land management and conservation and can affect the outcomes of development proposals and funding decisions. This process often relies on a species being proposed by an interested party and then a subsequent review of the proposal by an ‘expert’ panel. As can be seen from Table 10.1, the status of some species differs between the states and at the federal level. This is due

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Table 10.1 Current listing of conservation status of Australian mice and rats. Species Aus ACT NSW NT QLD SA TAS Vic WA White-footed rabbit EX PEX EX EN3 EX rat Brush-tailed rabbit VU rat Central short-tailed VU mouse Lesser stick-nest rat EX PEX EX EN3 EX PEX Greater stick-nest VU PEX VU RX RE rat Broad-toothed rat VU1 NT Bramble Cay EN EN melomys Golden-backed tree VU EN rat Short-tailed hopping EX EX PEX mouse Northern hopping VU VU VU mouse Fawn hopping PEX EN EN mouse Dusky hopping VU EN EN EN VU mouse Long-tailed hopping EX PEX EX PEX mouse Big-eared hopping EX PEX mouse Mitchell’s hopping PEX NT mouse Darling Downs EX EX hopping mouse Silky mouse EN NT Plains mouse VU PEX EN EN VU RE Bolam’s mouse EN RX Delicate mouse EN Desert mouse PEX RX Shark Bay mouse VU EX RE Smoky mouse EN EN EN EN Gould’s mouse EX PEX Eastern chestnut VU mouse Sandy inland mouse VU Western chestnut RE2 mouse

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Table 10.1 (continued)

Species Aus ACT NSW NT QLD SA TAS Vic WA New Holland mouse EN EN Hastings River EN EN VU mouse Pilliga mouse VU VU Heath mouse VU EN NT RE Basalt plains mouse EX Maclear’s rat Ex Bulldog rat EX Canefield rat DD Pale field rat EN3 Long-haired rat VU Water mouse VU DD VU Arnhem rock-rat VU VU Carpentarian EN CE rock-rat Central rock-rat EN EN RE Listings are those under the relevant schedules of Environment Protection and Biodiversity Conservation Act, 1999 (Federal); Nature Conservation Act 1980 (Australian Capital Territory); Threatened Species Conservation Act, 1995 (New South Wales); Territory Parks and Wildlife Conservation Act, 2000 (Northern Territory); Nature Conservation Act, 1992 (Queensland); National Parks and Wildlife Act, 1972 (South Australia); Threatened Species Protection Act, 1995 (Tasmania); Flora and Fauna Guarantee Act, 1988 (Victoria); Wildlife Conservation Act, 1950 (Western Australia). EX = extinct, extinct in wild (QLD), or presumed extinct (NSW and WA) RX= regionally extinct CE= Critically endangered EN = endangered (includes extinct taxa in SA) VU = vulnerable RE = rare or likely to become extinct in wild (only threatened taxon rank in WA) NT = near threatened DD= data deficient PEX = presumed extinct Notes: 1. Barrington Tops population listed as Endangered. 2. Barrow Island subspecies (P.n. ferculinus) only surviving population in WA- species listed under that taxon only. 3. Now extinct.

to the differing abundance of some species between states and, in some cases, to the use of different criteria and categories for listing by the different states. Basic knowledge of the species’ ecology is necessary when developing a conservation strategy. For instance, in developing appropriate conservation measures one needs to know the habitat requirement of a species, what foods it eats and whether feral species are having an impact on its surviving populations. A major problem with gathering this

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information today is that many native mice and rats, such as those in southern Australia, have already been so markedly affected by human presence that such ecological parameters, as now determined, may no longer reflect the original ecology of the species. Much of Australia is essentially a modified ecosystem, with most of the largest national parks containing introduced species that fill prominent roles as herbivores and predators. Weeds too are becoming increasingly abundant across the landscape. Partly due to geographical variation in ecological traits of a particular species, identification of suitable ‘management units’ is often used as an approach for effective conservation. Such management units within a species are based on geographical and ecological data. Genetical studies too can aid in the identification of groups or populations with shared histories and those currently isolated from other populations. For instance, Hastings River mouse populations fall into two distinct genetic groups. Conservation efforts should ideally be developed to save populations of all major lineages rather than focus on just a single population of a species. Similarly, a geographically isolated population of broad-toothed rats on Barrington Tops in New South Wales is treated as a distinct unit from the remainder of the species and is thus listed as endangered, although the species itself is only considered vulnerable in New South Wales (see Table 10.1).

Implementation of conservation management strategies Given the greatly contracted ranges and massive population declines of many species of native mice and rats, the task of recovering threatened species often appears daunting. However, recovery and management plans can be, and have been, put in place to minimise the likelihood of further extinctions of our native mice and rats. Acquisition of appropriate land for conservation reserves is clearly necessary to prevent further loss and fragmentation of appropriate habitat, but active land management needs to be carried out to control introduced carnivores and rabbits, and implementation of appropriate fire regimes is also required. In the case of endangered species it may be desirable to develop captive breeding programs, followed by translocation and reintroduction of individuals to predator-free islands and/or fenced-off areas from which cats, foxes and rabbits have largely, or completely, been precluded. A few

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such programs have been very successful in Australia (see Table 10.2). Perhaps the most striking example is that of the greater stick-nest rat which has now been downgraded from ‘endangered’ to ‘threatened’ in the IUCN Red List as a consequence of these reintroductions and translocations (see Tables 10.2 and 10.3).

Table 10.2 Translocation of species of conservation concern to islands or fenced-off mainland locations as a conservation strategy. Species Source Destination Successful establishment of breeding group Greater stick- Franklin Is Salutation Is, Shark Bay (WA) Yes nest rat (SA) St Peters Is (SA) Yes Reevesby Is (SA) Yes Roxby Downs (SA) Yes Yookamurra Sanctuary (SA) No Venus Bay Conservation Park (SA) Unknown Herisson Prong, Shark Bay (WA) Unknown Tropical short- Thevenard Is Serrurier Is (WA) Yes tailed mouse (WA) Shark Bay Bernier Is Doole Is, Exmouth Gulf (WA) Yes mouse (WA) Herisson Prong (WA) No Faure Is, Shark Bay (WA) Yes North West Is, Montebello Is (WA) Unknown

In south-eastern Australia, where much of the landscape has been extensively altered and subdivided, such successful reintroduction programs are not so easy to achieve. Where relatively natural habitats still occur, they are often in rugged terrain and difficult to actively manage by fencing off areas. In this situation, conservation of native mice and rats (such as the Hastings River mouse and smoky mouse) is often centred around land-management regimes such as forestry practices. Generally, conservation strategies have focussed on monitoring populations of the species of concern and carrying out measures such as fox control. This approach may ultimately prove insufficient and an active, experimental management approach may be required. If the species has become locally

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extinct, a re-introduction program would be necessary if some semblance of the natural rodent community is to be obtained. The frequency of fire is known to have a significant effect on population size of individual species, as well as on community composition (Chapter 7). In a few cases, management regimes are in place that actively promote persistence of particular species. For example, in the Little Desert region of north-western Victoria, moderately frequent burning is undertaken and has been found to favour formation of vegetation that produces important food for the silky mouse (Chapter 6). A burning regime with longer intervals from 15 to 40 or more years, has been proposed for heaths in which the smoky mouse occurs, but so far this regime has not been implemented. There are obvious risks in using fire as a management tool and there is a tendency to adopt a mosaic burning pattern of cool fires as a default management approach which should benefit many species of native mice and rats. However, when targeting key species it is probably necessary to experimentally determine the best burning regime for the particular species. Unfor tunately, for most threatened species, populations are currently too small and scattered, and too short-lived, to allow such experimentation. State government conservation departments and websites can provide up-to-date summaries of specific conservation action plans.

IUCN 2006 Red List The recently produced IUCN Red List classifies three species of native mice and rats as critically endangered, four as endangered, 11 as vulnerable, and six as near threatened (see Table 10.3). All except three of these species are members of Australian Old Endemic group. Thus, out of around 50 species of this group that were present at the time of European settlement, around 20% are now probably extinct (see Table 1.1), 12% are classified as critically endangered or endangered, another 18% as vulnerable, and around 12% as near threatened. This leaves only about half of the species in this group that were present 200 years ago as being of no current conservation concern. Most of these are small-bodied species. In stark contrast to the Old Endemics, none of the eight species of native Rattus, or New Endemics, is listed as threatened.

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Table 10.3 2006 IUCN Red Book listing of native Australian mice and rats Critically Endangered Vulnerable Near Threatened Endangered Central rock-rat Arnhem Land Hastings River Black-footed tree rock-rat mouse rat Carpentarian Smoky mouse Heath mouse Brush-tailed rock-rat rabbit rat Bramble Cay Pilliga mouse Kakadu pebble- Golden-backed melomys mound mouse tree rat Northern Shark Bay mouse Western mouse hopping mouse New Holland Broad-toothed rat mouse Fawn hopping Prehensile-tailed mouse rat Dusky hopping mouse Plains mouse Greater stick-nest rat Masked White- tailed rat Water mouse

Species of conservation concern Stick-nest rats Both the greater and lesser stick-nest rats appeared to have become extinct on the mainland by the 1950s but luckily a population of the greater stick- nest rat, discovered in 1922 on Franklin Island in the Nuyts Archipelago off the South Australian coast, has survived. Individuals from this population have been bred by the South Australian National Parks and Wildlife Service and Adelaide Zoo. The offspring produced in this captive colony have been reintroduced to reserves in Shark Bay in Western Australia and Roxby Downs in South Australia, as well as several other islands in these two states (see Table 10.2).

Plains mouse This is one of two species of native rodents that are occasionally kept as pets (the spinifex hopping mouse is the other). The captive plains mouse colonies are descendants of animals collected in the late 1960s and early 1970s in the north of South Australia and an adjacent region of the Northern

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Territory. No wild individuals were subsequently found between 1975 and 1990. However, since this time plains mice have been rediscovered at several localities to the west of Lake Eyre South and Lake Torrens, including near Roxby Downs and on the Moon Plains near Coober Pedy. No extant populations are known in the north-east of South Australia or on the Nullarbor Plain where they were present in the late 1960s, and no individuals of this species have been collected in central New South Wales or south-east Queensland for over 100 years. All extant populations are genetically similar, with one or more similar cryptic species probably having become extinct since the time of European settlement – for example the long-eared mouse, Pseudomys auritus, that was present in south-eastern South Australia.

Broad-toothed rat This species is now largely restricted to cold, wet alpine and subalpine areas of south-eastern Australia and button grass plains of Tasmania, but 200 years ago it was more widespread and common. Reasonable populations still occur in the Australian Alps, although there has been a marked decline over the past decade. The species also persists at lower altitudes in wet Victorian forests and in Tasmania, whereas the isolated northern population on Barrington Tops is apparently in decline and in need of assistance if it is to survive. Recent high-altitude declines of broad- toothed rat in the Snowy Mountains have been attributed to high rates of predation by foxes perhaps made easier due to reduced snow cover and shorter snow seasons which are possibly early signs of global warming.

Thevenard Island short-tailed mouse Although the tropical short-tailed mouse is known to occur across a wide area of northern Australia, an island form, with a considerably greater body mass than animals on the mainland, occurs on Thevenard Island off the north-west coast of Western Australia. Genetic studies have shown this form to be similar to the adjacent mainland populations, but it is nevertheless a population that constitutes a geographically and morphologically defined ‘management unit’. It is of concern because unfortunately, the house mouse has recently colonised the island and may now be in com petition with this native mouse species.

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Shark Bay mouse Subfossil deposits show that this species used to occur across a large area of central and western Australia. However there have only been two records of this species on the mainland since European settlement, both of which were before 1900. The species has, nevertheless, survived on Bernier Island in Shark Bay. Individuals from this population have been bred in captivity and released on Doole Island in Exmouth Gulf and Faure Island in Shark Bay where they now appear to be well established, although an attempt to develop a self-sustaining population in a fenced-off area on the mainland at Herisson Prong appears to have been unsuccessful (see Table 10.2).

Pilliga mouse This recently described species was thought to be restricted to the Pilliga scrub in northern New South Wales. However, it now appears that the Pilliga mouse is not a separate species but an isolated southern population of the delicate mouse, with another population having recently been dis covered closer to the Queensland border. Although these populations do not now appear to represent a distinct species, they are remnants of an inland native rodent fauna of New South Wales. The Pilliga population is of special significance as it is still large enough to undergo natural population fluctuations, including occasional irruptions following fire.

Rock-rats There are two species of large rock-rats of particular conservation concern. The first is the central rock-rat, which was once widespread from the Pilbara to the Central Australian ranges. It was thought to have become extinct in the 1960s, but in 1996 a small extant population was discovered in the MacDonnell Ranges to the west of Alice Springs. Since that time these animals have been found in very low densities over a 77 km strip of the ranges. The second species of rock-rat of concern is the Carpentarian rock-rat, which is restricted to a few small populations in localised areas of monsoon thickets on boulder scree slopes on a single cattle station. Such patches of forest are threatened by feral animals and altered fire regimes thus endangering the survival of this species.

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Smoky mouse Bone deposits in south-eastern Australia from the last 1000 years indicate that the smoky mouse was once a common and widespread species. Today it is very rare. A few relatively large populations were found in the Grampians and near the New South Wales/Victorian border 20 to 30 years ago but since that time large populations have proved hard to locate. It is a difficult species to actively manage as populations often disappear soon after they are detected. Furthermore, individuals of this species are sometimes found in habitats that are markedly different from the heathy habitats thought to be favoured by this species. Forest managers and national parks staff in southern New South Wales have devised a management strategy for this species that involves creating reserves for protection of core habitat, together with an investigation into the effects of logging and fire on habitat quality.

Hastings River mouse Although two specimens of this species were collected in the 1800s, it was thought for many years to be extinct until it was rediscovered in 1968 near Warwick in south-east Queensland. This species is rare but has been caught in a variety of forest types and understoreys from Barrington Tops in New South Wales to southern Queensland. Bone deposits show that it used to occur in highlands of the coastal escarpment, in the Australian Alps, and as far west as the Pilliga scrub 200 years ago. There is considerable debate over appropriate management strategies for this species, but the frequency of logging and burning regimes, as well as grazing intensity, may be important factors for its survival.

New Holland mouse This south-eastern Australian species has undergone a massive range contraction. It was collected on several occasions in the 19th century up until 1887 and then thought to be extinct until its rediscovery near Sydney in 1967. Populations have subsequently been recorded from coastal Victoria and the coastal heaths of north-east Tasmania and, in 1996, a single population was found in southern Queensland. It is relatively widespread in north-eastern New South Wales. The recent discovery of an inland population near Parkes, New South Wales has revived some hope of finding more populations of what was probably a

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common resident of forest understoreys from the cooler parts of south- eastern Queensland near Toowoomba to the Victorian/South Australian border. Several Victorian populations appear to have become extinct in the recent past.

Water mouse This is an elusive species with a few scattered populations found along the Northern Territory and Queensland coasts and it has recently also been found in southern New Guinea. The species has probably suffered from reclamation of swamps and clearing of mangroves, as well as from feral predators and fragmentation of habitat. A population that was being monitored in south-east Queensland declined to apparent extinction over a period of seven years, possibly due to housing development and/ or regular spraying of swamp habitats with insecticide for control of mosquitoes.

Bramble Cay melomys This species of melomys is of concern due to its restriction to Bramble Cay, a single, very small, offshore island in the Torres Strait. Any alteration to its circumstances, such as introduction of a competitor or predator, erosion of the cay, or inundation due to sea level rise, could lead to its demise.

Tree and rabbit rats The large tree rats of northern Australia show signs of decline in distribution and abundance. For instance, the golden-backed tree rat has not been caught in the Pilbara region for over 100 years and there have only been anecdotal reports of its presence in the Northern Territory since 1969. This species now appears to be localised to the northern Kimberley. The black-footed tree rat is still thought to be common in a few places in the Northern Territory but it has declined markedly in Kakadu National Park, possibly due to increased incidence of extensive wildfires. On Cape York it is a rare animal that occurs in scattered populations. The brush- tailed rabbit rat used to be quite widespread in the northern part of the Northern Territory but has declined considerably over the last 20 or so years, although it is present on Bentinik, Inglis and the Tiwi Islands. The recent forestry plantations of Acacia magnum on the Tiwi Islands could pose a major threat to this species.

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Hopping mice The hopping mice as a group have been greatly reduced over the last 200 years, with probably half of the 10 hopping mouse species having become extinct during this time. All the large-bodied species (which were roughly twice the weight of extant species), now seem to be extinct, with the last individuals being collected around 1902. Two species, the spinifex hopping mouse and Mitchell’s hopping mouse are, however, still quite widespread. The other three species have small ranges. The northern hopping mouse has not been recorded in Queensland since 1867 and now appears to be restricted to Groote Eylandt and an adjacent small region on the mainland in north-east Arnhem Land. The dusky hopping mouse is patchily distributed in the north-east of South Australia, the far north-west corner of New South Wales and south-west Queensland, with some of the surviving populations occurring in highly degraded habitat. Its greatly reduced range may well be due, at least in part, to overgrazing by rabbits.

Heath mouse Although this species was collected near Perth in the early 1900s, it was not found again until 1961 when some individuals were collected in the Grampians in western Victoria. It is now known from a number of localities in western Victoria and in 1987 it was again found in Western Australia in Fitzgerald River National Park. It has since been recorded from three other Western Australian locations near Ravensthorpe and Lake Magenta. Studies of the Victorian and Western Australian populations suggest preferences for different post-fire successional stages, thus complicating management plans using patch burning of its habitat based on a species- level preference. A ‘management unit’ approach, which adopts the best practice for the different populations of each state, appears to be the most appropriate conservation strategy for this species.

Pale field rat This species is now restricted to grasslands and grassy eucalypt woodlands of northern Australia, but it used to occur much further south. In the recent past its range has probably declined to around 10% of what it was previously. Since the pale field rat appears to be largely dependent on riparian vegetation, its range contraction may have been brought about by the grazing of introduced livestock.

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Are there native mice and rats near you? Many native species are present in low densities and do not occur close to human habitation so it is unlikely that you will ever see most of the native mice and rats in your area. Apart from water rats, most are small, move fast and are nocturnal. In tropical rain forests it is possible to see giant white-tailed rats and melomys if you go spotlighting. Elsewhere you are likely to catch only an occasional brief glimpse of a native mouse or rat as it runs or hops across a road although there may be other signs that can alert you to their presence. For instance, water rats have feeding ‘tables’ on rocks in, or near, rivers, that are littered with remains of their food such as pieces of exoskeletons of yabbies. Broad-toothed rats and swamp rats make distinctive runways through vegetation, and even the smallest mice can leave tracks in areas where there is a sandy or muddy surface substrate. It is often difficult to distinguish rodent burrows from those of other animals, although hopping mouse and pebble-mound mouse burrow entrances are easily identifiable (see Chapter 8 Specialised home bases). Droppings of predators such as dogs and foxes also often contain remains of mice and/or rats. These carnivores are much more skilled at finding mice and rats than even ‘expert’ human researchers. Research workers at natural history museums, universities, or relevant state environment departments can sometimes help by examining hair or bones from scats to assist in the identification of species.

a b c Track of a bounding sandy inland mouse on a Simpson Desert dune (a); pebble craters highlight the burrow entrances of a central pebble-mound mouse in the Davenport ranges (b); and a broad-toothed rat runway through subalpine grass and heath (c).

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Abundance the total number of organisms occurring in a speciﬁ c area. Auditory bulla a hollow, bony structure that surrounds much of the middle and inner ear.

Biogeography the study of the geographical distribution of organisms. Biostratigraphic date a time during which one group of fossils existed. Biota the complete fauna and ﬂ ora of a particular region. Caecum a region of gut where fermentation of plant material may occur. Cenozoic a geological period of time ranging from 65 to 1.5 million years ago. Chenopods a group of water-hoarding and salt tolerant Australian plants that include saltbushes, bluebushes and samphires that are common in parts of the arid zone.

Commensal a relationship where one species beneﬁ ts from coexistence with relationship another species. Convergent evolution the independent evolution of similar structure or form. Cusp a point or projection on the crown of a tooth. Dental formula the numbers of the four types of teeth (incisors, canines, premolars and molars) present in the jaw of a particular mammalian species. Top number indicates numbers of each of four types of teeth in upper jaw and lower number in the lower jaw. Dentine a part of tooth that occurs beneath or behind the enamel and includes calcium phosphate as well as organic material. Diastema a gap in a row of teeth (often between the incisors and molars). Disease a condition of abnormal vital function involving any structure, part or system of an organism resulting from various causes, such as infection, genetic defect or environmental stress, and characterised by an identiﬁ able group of signs or symptoms. Divergent evolution the evolution of dissimilar structure or form. Diversity the absolute number of species in a particular area or community. Enamel the hardest part of a tooth, often on its outer surface. Endangered threatened with extinction. Endemic native and restricted to a particular geographical region. Extant living at the present time.

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Extinct no longer living or in existence. Glenoid fossa a depression in the posterior part of the zygomatic arch of the skull into which the lower jaw inserts. Hindgut the last part of the gastrointestinal tract. Holocene a geological period of time ranging from 100 000 years ago to present time. Karyotype chromosome complement of a cell. Karyotyping determination of the chromosome complement of a cell. Lineage a line of common descent. Lingual towards the tongue. Miocene a geological period of time ranging from 25 to 5 million years ago. Monogamous pair one male and one female forming an exclusive breeding unit. Morphology the study of form and structure. Multivariate analysis simultaneous statistical analysis of more than one independent variable. Murid a family of rodents that includes murine rodents as well as gerbils and a small African group of spiny mice. Murine a subfamily of rodents that includes the rats and mice occurring in the Old World. Muroidea a superfamily that includes murid rodents and New World rodents such as deer mice, hamsters, voles, lemmings and their allies, as well as pouched mice and related forms from Africa.

New World North and South America. Occlusal surface a part of a tooth that closes against the tooth of the other jaw. Old World Africa, Eurasia and Australasia. Parasite an organism that grows, feeds and is sheltered on, or in, a different organism while contributing nothing to the survival of its host (e.g. tapeworm, fl ea, most bacteria, virus). Pathogen an agent or organism that causes disease. Pleistocene a geological period of time ranging from 1.6 to 100 000 years ago. Pliocene a geological period of time ranging from 5 to 1.6 million years ago. Polyandrous a breeding system where a female mates with more than one male. Radiometric confi rmation of rock age by determining the amount of decay of confi rmation a particular element.

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Reciprocal the exchanging of segments between two chromosomes. translocation Riparian living close to the banks of streams or rivers. Robertsonian fusion the union between two or more chromosomes to form a single chromosome. Scansorial climbing. Selective pressure an environmental factor that results in natural selection. Site ﬁ delity restriction of species to a particular location (usually used for plants). Speciate the formation of a new species resulting from the inability of individuals of one population to produce fertile offspring by mating with members of another population. Species distribution the geographical range of a species. Taxon (taxa pl) a group of organisms that is distinct from all other groups such that it can be considered a separate and distinct unit. Taxonomy the study of describing, naming and classifying organisms. Vibrissae the modiﬁ ed hairs or whiskers around the mouth of an organism.

Zygomatic arch a bony structure that forms part of the ﬂ oor and lateral wall of the orbit.

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Tate GHH (1951). The rodents of Australia and New Guinea. In Results of the Archbold Expeditions No 65. Bulletin of the Museum of Natural History 97, 187–430. Taylor JM, Calaby JH and Smith SC (1983). Native Rattus, land bridges, and the Australian region. Journal of Mammalogy 64, 463–475. Tedford RH and Wells RT (1990). Pleistocene deposits and fossil vertebrates from the ‘dead heart of Australia’. Memoirs of the Queensland Museum 28, 263–284. Theimer TC (2001). Seed scatter-hoarding by white-tailed rats: consequences for seeding recruitment by an Australian rainforest tree. Journal of Tropical Ecology 17, 177–189. Thompson P and Fox BJ (1993). Asymmetric competition in Australian heathland rodents: a reciprocal removal experiment demonstrating the influence of size and class structure. Oikos 67, 264–278. Trainor C (1998). Carpentarian rock-rat. Nature Australia 26(1), 20–21. Trainor C, Fisher A, Woinarski J and Churchill S (2000). Multiscale patterns of habitat use by the Carpentarian rock-rat (Zyzomys palatalis) and the common rock-rat (Z. argurus). Wildlife Research 27, 319–332. Triggs B (1996). Tracks, Scats, and Other Traces. A Field Guide to Australian Mammals. Oxford University Press, Melbourne. Troughton E (1967). Furred Animals of Australia. 9th Edition. Angus and Robertson, Sydney. Van Dyck S (1991). A little secret from the Masons. Wildlife Australia 28, 18–19. Van Dyck S (1997). Queensland pebble-mouse mice … up from the tailings. Nature Australia 25(10), 40–47. Van Dyck S (1997). Xeromys myoides Thomas, 1889 (Rodentia: Muroidea) in mangrove communities of North Stradbroke Island, Southeast Queensland. Memoirs of the Queensland Museum 42, 337–366. Van Dyck S (1997). The New Holland mouse Pseudomys novaehollandiae (Rodentia: Muridae) an addition to the mammal fauna of Queensland. Memoirs of the Queensland Museum 42, 367–376. Van Dyck SM (1998). New Holland mouse. Nature Australia 26(3), 48–53. Vazquez-Dominguez E, Paetkau D, Tucker N, Hinten G and Moritz C (2001). Resolution of natural groups using iterative assignment tests: an example from two species of Australian native rats (Rattus). Molecular Ecology 10, 2069–2078. Wakefield NA (1972). Palaeoecology of fossil mammal assemblages from some Australian caves. Proceedings of the Royal Society of Victoria 85, 1–26. Warner LR (1998). Australian helminths in Australian rodents: An issue of biodiversity. International Journal for Parasitology 28, 839–846. Watts CHS (1976). Leggadina lakedownensis, a new species of murid rodent from north Queensland. Transactions of the Royal Society of South Australia 100, 105–108. Watts CHS (1977). The foods eaten by some Australian rodents (Muridae). Australian Wildlife Research 4, 151–157. Watts CHS and Aslin H (1981). The Rodents of Australia. Angus and Robertson, Sydney. Watts CHS and Kemper CM (1989). Muridae. In Fauna of Australia. Mammalia (eds DW Walton and BJ Richardson) pp. 939–956. Australian Government Publishing Service, Canberra. Watts CHS, Baverstock PR, Burrell J and Kreig M (1992). Phylogeny of the Australian rodents (Muridae): a molecular approach using microcomplement fixation of albumin. Australian Journal of Zoology 40, 81–92. Wells RT, Moriarty K and Williams DLG (1984). The fossil vertebrate deposits of Victoria Fossil Cave Naracoorte: an introduction to the geology and fauna. Australian Zoologist 21, 305–333.

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Williams CK (1987). Water physiology and nutrition in fluctuating populations of Rattus colletti in monsoonal Northern Territory, Australia. Australian Wildlife Research 14, 443–458. Wilson BA and Friend GA (1999). Responses of Australian mammals to disturbance: a review. Australian Mammalogy 21, 87–105. Wilson BA and Laidlaw WS (2003). Habitat characteristics for New Holland Mouse Pseudomys novaehollandiae in Victoria. Australian Mammalogy 25, 1–11. Winter JW (1997). Responses of non-volant mammals to Late Quaternary climate changes in the Wet Tropics region of north-eastern Australia. Wildlife Research 24, 493–511. Winter JW (1984). The Thornton Peak Melomys, Melomys hadrourus (Rodentia: Muridae): a new rainforest species from northeastern Queensland, Australian. Memoirs of the Queensland Museum 21, 519–539. Woinarski JCZ (1992). Habitat relationships for two poorly known mammal species Pseudomys calabyi and Sminthoposis sp. from the wet-dry tropics of the Northern Territory. Australian Mammalogy 15, 47–54. Woinarski JCZ (2000). The conservation status of rodents in the monsoonal tropics of the Northern Territory. Wildlife Research 27, 421–435. Woinarski JCZ, Gambold N, Wurst D, Flannery TF, Smith AP, Chatto R and Fisher A (1999). Distribution and habitat of the northern hopping mouse, Notomys aquilo. Wildlife Research 26, 495–511. Woinarski JCZ, Milne DJ and Wanganeen G (2001). Changes in mammal populations in relatively intact landscapes of Kakadu National Park, Northern Territory, Australia. Austral Ecology 26, 360–370. Wood Jones F (1968). The Mammals of South Australia. AB James, Adelaide. Woods RE and Ford FD (2000). Observation on the behaviour of the smoky mouse Pseudomys fumeus (Rodentia: Muridae). Australian Mammalogy 22, 35–42. Woolard P, Vestjens WJM and MacLean L (1978). The ecology of the Eastern water rat, Hydromys chrysogaster at Griffith, NSW: food and feeding habits. Australian Wildlife Research 5, 59–73. Yom-Tov Y (1985). The reproductive rates of Australian rodents. Oecologia 66, 250–255.

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Figure references are in bold community structure 121 conservation 152, 154, 157, 158, 163 arid zone 41, 45–7 dentition and diet 102, 103, 104, 108, 109 Arnhem Land rock-rat (Zyzomys maini) 9, distribution and habitat 53 30, 82 female reproductive characteristics 96 conservation 153, 157 fossils 57, 58, 59 distribution and habitat 43, 44 gastrointestinal tract 113, 114 see rock-rats phylogeny 63, 64 ash-grey mouse (Pseudomys albocinereus) 8, seasonal dynamics 119 24 social organisation and behaviour 129, distribution and habitat 51, 52 132 origin and evolution 68 brown rat (Rattus norvegicus) 9, 38 seasonal dynamics 119 female reproductive characteristics 98 social organisation and behaviour 131 origin and evolution 64 parasites and disease 143, 145, 147 big-eared hopping mouse (Notomys reproductive potential 87 macrotis) 8, 21, 51, 52 skull 106 see hopping mice see introduced species black-footed tree rat (Mesembriomys gouldii) brush-tailed rabbit rat (Conilurus 5, 8, 20 pencillatus) 8, 17, 71 conservation 157, 161 conservation 152, 157, 161 dentition and diet 103, 104 distribution and habitat 44, 48 distribution and habitat 44, 49 gastrointestinal tract 113 female reproductive characteristics 96 origin and evolution 62 gastrointestinal tract 113 seasonal dynamics 119 home range 116 see rabbit rats origin and evolution 69 burrows 129–35, 130, 131 seasonal dynamics 119 bush rat (Rattus fuscipes) 1, 9, 10, 36, 37 social organisation and behaviour 133 community structure 121, 122, 124 black rat (Rattus rattus) 2, 9, 37, 38 conservation 149 origin and evolution 64 diet and dentition 103, 105 parasites and disease 146 distribution and habitat 42, 46, 47, 48, reproductive potential 87 49, 51, 53, 54 see introduced species female reproductive characteristics 95 blue-grey mouse (Pseudomys glaucus) 8, 24, fire, response to 120, 121 49, 52 fossils 58, 59 Bolam’s mouse (Pseudomys bolami) 8, 25, 75 home range 116 conservation 152 origin and evolution 64 distribution and habitat 45, 46, 51, 53 parasites and disease 141, 142, 143, 145, fossils 59 146 Bramble Cay melomys (Melomys rubicola) seasonal dynamics 119 9, 31 social organisation 133, 134 conservation 152, 157, 161 testis size 89 see mosaic-tailed rats see native Rattus broad-cheeked hopping mouse (Notomys sp.) 8, 21–2 canefield rat (Rattus sordidus) 9, 36 see hopping mice conservation 149, 153 broad-toothed rat (Mastacomys fuscus) 5, 8, diet 105 26, 78 distribution and habitat 37, 44, 47, 49

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female reproductive characteristics 95, 96 community structure 121, 122, 123 origin and evolution 64 conservation 152, 159 parasites and disease 140, 143 distribution and habitat 44, 46, 49–50, 53 plagues 118 female reproductive characteristics 96 seasonal dynamics 119 fire, response to 120 social organisation 134 male reproductive characteristics 89, see native Rattus 90, 91 Cape York melomys (Melomys capensis) 9, origin and evolution 62 31 phylogeny 63, 64, 69 distribution and habitat 47, 48 dentition 4, 63, 102–9, 106–8, 110 seasonal dynamics 118 desert mouse (Pseudomys desertor) 9, 28, 80 see mosaic-tailed rats conservation 152 Cape York rat (Rattus leucopus) 9, 36 dentition and diet 102, 103 distribution and habitat 37, 47, 48, 49 distribution and habitat 44, 46, 49, 50, female reproductive characteristics 95, 51, 53 96 female reproductive characteristics 96 home range 116 fire, response to 120 origin and evolution 64 fossils 58 parasites and disease 147 plagues 117 seasonal dynamics 118, 119 seasonal dynamics 119 see native Rattus social organisation and behaviour 129, Carpentarian rock-rat (Zyzomys palatalis) 132, 133, 138 9, 30 testis size 89 conservation 153, 157, 159 desert short-tailed mouse (Leggadina distribution and habitat 43 forresti) 8,18, 71 see rock-rats distribution and habitat 44, 46 central rock-rat (Zyzomys pedunculatus) 9, female reproductive characteristics 96 30 seasonal dynamics 119 conservation 153, 157, 159 see short-tailed mice diet 102 diet 101–5 distribution and habitat 46, 50 diseases 147–8 see rock-rats dispersal 116–7 central pebble-mound mouse (Pseudomys dusky hopping mouse (Notomys fuscus) 8, johnsoni) 8, 27 21–2, 73 distribution and habitat 44, 46 conservation 152, 157, 162 see pebble-mound mice distribution and habitat 45, 46 common rock-rat (Zyzomys argurus) 9, 30, 82 evolution 65 distribution and habitat 42, 44, 46, 47, female reproductive characteristics 96 48, 49, 50 plagues 117 female reproductive characteristics 96 seasonal dynamics 119 origin and evolution 69 social organisation and behaviour 131 see rock-rats see hopping mice Conilurus sp. see rabbit rats dusky rat (Rattus colletti) 9, 36 Conilurus albipes see white-footed rabbit dispersal 116 rat distribution and habitat 37 Conilurus pencillatus see brush-tailed female reproductive characteristics 95, rabbit rat 96, 98 origin and evolution 64, 69 Darling Downs hopping mouse (Notomys plagues 118 mordax) 8, 21 seasonal dynamics 119 see hopping mice sexual maturity 99 delicate mouse (Pseudomys delicatulus) 5, 8, see native Rattus 10, 11, 25, 27, 77

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eastern chestnut mouse (Pseudomys see mosaic-tailed rats gracilicaudatus) 8, 26 golden-backed tree rat (Mesembriomys community structure 119, 121, 122, 123 macrurus) 8, 14, 20, 72 conservation 152 conservation 152, 157, 161 dentition and diet 109 distribution and habitat 44, 50, 51 distribution and habitat 46, 49, 53, 58 social organisation and behaviour 133 fire, response to 120 see tree rats phylogeny 62 Gould’s mouse (Pseudomys gouldii) 9, 29 seasonal dynamics 118, 119 distribution and habitat 46, 51–53 eastern pebble-mound mouse (Pseudomys grassland melomys (Melomys burtoni) 9, 31 patrius) 8, 27 conservation 149 distribution and habitat 48, 49 distribution and habitat 44, 47, 49, 53 movements and home range 116 female reproductive characteristics 96 seasonal dynamics 118, 119 gastrointestinal tract 113 social organisation and behaviour 135 seasonal dynamics 119 see pebble-mound mice social organization and behaviour 133 external genitalia 93–4 see mosaic-tailed rats ‘grassland’ melomys (Melomys lutillus) 9, 31 fawn-footed melomys (Melomys cervinipes) greater stick-nest rat (Leporillus conditor) 8, 9, 31, 83 19, 72, 137 dentition and diet 103 conservation 152, 155, 157 distribution and habitat 47, 48, 49, 53 dentition and diet 104, 108, 109, 112 female reproductive characteristics 96 distribution and habitat 42, 45, 46, 51, fossils 58 53, 59 gastrointestinal tract 112 evolution 65 origin and evolution 65 female reproductive characteristics 99 parasites and disease 142, 143 gastrointestinal tract 114 seasonal dynamics 118, 119 parasites and disease 148 social organization and behaviour 133 seasonal dynamics 119 see mosaic-tailed rats social organisation and behaviour 135, fawn hopping mouse (Notomys cervinus) 8, 136 10, 21–2, 73 see stick-nest rats conservation 152, 157 distribution and habitat 45, 46, 59 Hastings River mouse (Pseudomys oralis) 9, female reproductive characteristics 96, 29 99 conservation 153, 154, 155, 157, 160 fire, response to 119–21, 123 dentition and diet 102, 109 fossils 56, 60, 61 distribution and habitat 53 male reproductive characteristics 90, 92 fire, response to 120 see hopping mice fossils 58, 59, 60 seasonal dynamics 119 gastrointestinal tract 109, 111–, 112, 113, 114 heath mouse (Pseudomys shortridgei) 9, 28, 80 giant white-tailed rat (Uromys conservation 153, 157, 162 caudimaculatus) 9, 32, 83 dispersal 117 conservation 163 distribution and habitat 51, 53 dentition and diet 104, 109, 110 fire, response to 120 distribution and habitat 42, 47, 48, 49 fossils 58 female reproductive characteristics 96, 99 male reproductive characteristics 89, gastrointestinal tract 111, 112, 113, 114 90, 91 male reproductive characteristics 89, 91 origin and evolution 69 parasites and diseases 143 social organisation and behaviour 128, seasonal dynamics 119 132 social organization and behaviour 133 home ranges 116

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hopping mice (Notomys sp.) 5, 8, 21–2 Leggadina lakedownensis see tropical short- conservation 162 tailed mouse distribution and habitat 40, 42, 45, 50–2 Leporillus sp. see stick-nest rats female reproductive characteristics 94, Leporillus apicalis see lesser stick-nest rat 95, 98, 99, 100 Leporillus conditor see greater stick-nest fossils 56, 57, 58, 59, 61 rat gastrointestinal tract 111, 113 lesser stick-nest rat (Leporillus apicalis) 8, 19 male reproductive characteristics 89, 90, distribution and habitat 46, 51, 53 91, 92, 93 fossils 57, 59 origin and evolution 66, 68 see stick-nest rats phylogeny 63, 64, 67 litter size 94–6, 97 social organisation and behaviour 127, long-eared mouse (Pseudomys auritus) 8, 23 128, 129, 131 long-haired rat (Rattus villosissimus) 9, 36, see dusky hopping mouse 37, 86 see fawn hopping mouse conservation 153 see Mitchell’s hopping mouse dispersal 117 see northern hopping mouse distribution and habitat 44, 46, 49 see spinifex hopping mouse female reproductive characteristics 96 house mouse (Mus musculus) 2, 9, 15, 18, 38 origin and evolution 59, 64, 66, 69 community structure 122, 123 plagues 117, 118 conservation 149, 158 seasonal dynamics 119 dentition 4, 106 social organisation and behaviour 134 female reproductive characteristics 94, see native Rattus 98 long-tailed hopping mouse (Notomys male reproductive characteristics 92 longicaudatus) 8, 21, 46, 51 origin and evolution 59, 68 see hopping mice parasites and disease 145–147 long-tailed mouse (Pseudomys higginsi) 8, 23 plagues 117, 118 conservation 152 reproductive potential 87 distribution and habitat 46, 51, 53, 57 see introduced species female reproductive characteristics 96 Hydromys chrysogaster see water rat fossil 58, 59 ‘Hydromys group’ 7, 9 parasites and disease 143 seasonal dynamics 119 introduced species 2, 3, 9, 13, 15, 37, 38, 87 social organisation 132 see black rat male accessory sex glands 91–2, 93 see brown rat male reproductive characteristics 88, 89, 91, see house mouse 93, 94 see Pacific rat masked white-tailed rat (Uromys hadrourus) 9, 32 Kakadu pebble-mound mouse (Pseudomys distribution and habitat 47 calabyi) 8, 27 see mosaic-tailed rats distribution and habitat 44 Mastacomys fuscus see broad-toothed rat see pebble-mound mice mating behaviour 93 Kimberley rock-rat (Zyzomys woodwardi) 9, Melomys sp. see mosaic-tailed rats 30 Melomys burtoni see grassland melomys distribution and habitat 43, 44 Melomys capensis see Cape York melomys see rock-rats Melomys cervinipes see fawn-footed melomys lactation 98–100 Melomys lutillus see ‘grassland’ melomys Leggadina sp. see short-tailed mice Melomys rubicola see Bramble Cay Leggadina forresti see desert short-tailed melomys mouse Mesembriomys sp. see tree rats

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Mesembriomys gouldii see black-footed plagues 118 tree rat seasonal dynamics 118, 119 Mesembriomys macrurus see golden- sexual maturity 99 backed tree rat social organisation and behaviour 133, Mitchell’s hopping mouse (Notomys 134, 138 mitchelli) 6, 8, 10, 21–2, 74 see bush rat conservation 152, 162 see canefield rat distribution and habitat 45, 46, 51, 53 see Cape York rat female reproductive characteristics 96 see dusky rat gastrointestinal tract 112 see long-haired rat seasonal dynamics 119 see pale field rat social organisation and behaviour 131 see swamp rat sperm morphology 91 New Holland mouse (Pseudomys see hopping mice novaehollandiae) 8, 25 mosaic-tailed rats (Melomys and Uromys) 5, community structure 122, 123 7, 9, conservation 153, 157, 160 community structure 122, 123 diet 102 dentition and diet 104, 109 distribution and habitat 53 distribution and habitat 40, 42, 45, 48 female reproductive characteristics 96 female reproductive characteristics 98 fire, response to 120 fossils 56 fossils 58, 59 gastrointestinal tract 114 seasonal dynamics 119 home range 116 north-east dry forests 41, 43, 48–9 litter size 95 north-east wet forests 42, 47–8 male reproductive characteristics 92 north-western delicate mouse (Pseudomys origin and evolution 61, 62, 64, 65, 67, 70 sp.) 8, 25 phylogeny 63 northern hopping mouse (Notomys aquilo) social organization and behavior 133 8, 21–2 see Bramble Cay melomys conservation 152, 157, 162 see Cape York melomys distribution and habitat 44 see fawn-footed melomys social organisation and behaviour 127, see giant white-tailed rat 131 see grassland melomys see hopping mice see masked white-tailed rat northern savannah 41, 43–5 Mus musculus see house mouse Notomys sp. see hopping mice Notomys alexis see spinifex hopping native Rattus 7, 9, 36–7 mouse community structure 121, 122, 123, 124 Notomys amplus see short-tailed hopping conservation 156 mice diet 105 Notomys aquilo see northern hopping distribution and habitat 42, 43, 45, 47–9, mouse 53–4 Notomys cervinus see fawn hopping female reproductive characteristics 95, mouse 99, 100 Notomys fuscus see dusky hopping mouse fossils 65, 57, 59 Notomys longicaudatus see long-tailed litter size 97, 98 hopping mouse male reproductive characteristics 90, Notomys macrotis see big-eared hopping 91, 93 mouse origin and evolution 61, 62, 64, 65, 66, Notomys mitchelli see Mitchell’s hoping 67, 69, 70 mouse parasites and disease 140, 141 Notomys mordax see Darling Downs phylogeny 63 hopping mouse

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Notomys sp. see broad-cheeked hopping prehensile-tailed rat (Pogonomys sp.) 5, 7, mouse 9, 35, 85 community structure 122 ovulation rate 94–5, 98 conservation 157 dentition and diet 109, 110 Pacific rat (Rattus exulans) 9, 15, 38 distribution and habitat 42, 47 see introduced species origin and evolution 61, 62, 67 pale field rat (Rattus tunneyi) 9, 36–7, 86 phylogeny 63 community structure 123 ‘Pseudomys group’ 5, 8, 61 conservation 153, 162 Pseudomys albocinereus see ash-grey mouse distribution and habitat 44, 46, 47, Pseudomys apodemoides see silky mouse 49–51, 53 Pseudomys auritus see long-eared mouse female reproductive characteristics 95, Pseudomys australis see plains mouse 96 Pseudomys bolami see Bolam’s mouse fossils 59 Pseudomys calabyi see Kakadu pebble- origin and evolution 64 mound mouse seasonal dynamics 119 Pseudomys chapmani see western pebble- see native Rattus mound mouse parasites Pseudomys delicatulus see delicate mouse bacteria 145–6 Pseudomys desertor see desert mouse ectoparasites: ticks, mites and fleas 142 Pseuodmys fieldi see Shark Bay mouse protozoa 143, 144, 145 Pseudomys fumeus see smoky mouse worms 140–2 Pseudomys glaucus see blue-grey mouse peat mounds 136, 137 Pseudomys gouldii see Gould’s mouse pebble-mound mice 8, 16, 27 Pseudomys gracilicaudatus see eastern community structure 123 chestnut mouse conservation 163 Pseudomys hermannsburgensis see sandy movements and home ranges 116 inland mouse phylogeny 64 Pseudomys higginsi see long-tailed mouse social organisation and behaviour 134, Pseudomys johnsoni see central pebble- 135 mound mouse see central pebble-mound mouse Pseudomys nanus see western chestnut see eastern pebble-mound mouse mouse see Kakadu pebble-mound mouse Pseudomys novaehollandiae see New Holland see western pebble-mound mouse mouse pebble mounds 134–5, 135 Pseudomys occidentalis see western mouse Pilbara 18, 27, 39, 41, 45, 50–1, 69 Pseudomys oralis see Hastings River mouse plagues 117–8 Pseudomys patrius see eastern pebble-mound plains mouse (Pseudomys australis) 8, 23, 75 mouse conservation 152, 157, 158 Pseudomys shortridgei see heath mouse distribution and habitat 46, 49, 52, 53 Pseudomys sp. see north-western delicate evolution 65, 67 mouse female reproductive characteristics 96, 99 fossils 59 rabbit rats (Conilurus sp.) 8, 17 male reproductive characteristics 89, 91, conservation 161 92, 93 diet 104 plagues 119 distribution 42 seasonal dynamics 119 phylogeny 64 social organisation and behaviour 128, seasonal dynamics 118 129, 131 see brush-tailed rabbit rat ‘Pogonomys group’ 7, 9 see white-footed rabbit rat Pogonomys sp. see prehensile-tailed rat Rattus colletti see dusky rat pregnancy length 98–100 Rattus exulans see Pacific rat

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Rattus fuscipes see bush rat see desert short-tailed mouse Rattus leucopus see Cape York rat see tropical short-tailed mouse Rattus lutreolus see swamp rat silky mouse (Pseudomys apodemoides) 8, 24, Rattus norvegicus see brown rat 76 Rattus rattus see black rat conservation 152, 156 Rattus sordidus see canefield rat dentition and diet 102, 103 Rattus tunneyi see pale field rat distribution and habitat 53 Rattus villosissimus see long-haired rat female reproductive characteristics 96 rock-rats (Zyzomys sp.) 5, 9, 30 fire, response to 120 behaviour 99 fossils 57, 58, 59 community structure 121, 123 gastrointestinal tract 111 conservation 159 male reproductive characteristics 89 distribution and habitat 43, 48 origin and evolution 68 fossils 57 seasonal dynamics 119 home ranges 116 social organisation and behaviour 127, origin and evolution 68, 69 131 phylogeny 63 skulls 4, 106, 107, 108, 110 see Arnhem Land rock-rat smoky mouse (Pseudomys fumeus) 8, 24, 76 see Carpentarian rock-rat conservation 152, 155, 156, 157, 159 see central rock-rat diet 102 see common rock-rat distribution and habitat 53, 57 see Kimberley rock-rat fire, response to 120 fossils 58, 59 sandy inland mouse (Pseudomys seasonal dynamics 119 hermannsburgensis) 8, 25, 77 social organisation and behaviour 132, community structure 122 138 conservation 152, south-east region 41, 52–4 dentition and diet 102, 103 south-west region 41, 51–2 distribution and habitat 44, 46, 49, 50–51 sperm morphology 90, 91 female reproductive characteristics 96 spinifex hopping mouse (Notomys alexis) 8, fire, response to 120 21–2 fossils 59 conservation 162 gastrointestinal tract 111 dentition and diet 102, 103, 107, 108 male reproductive characteristics 94 distribution and habitat 45, 46, 50, 51 movements and home range 117 evolution 67 origin and evolution 66 female reproductive characteristics 96, plagues 117 97 seasonal dynamics 119 male reproductive characteristics 89, 90, social organisation 132 92, 93, 94 seasonal dynamics 118–9, 119 parasites and disease 142, 145, 147 Shark Bay mouse (Pseudomys fieldi) 8, 23 plagues 117 conservation 152, 155, 157, 159 seasonal dynamics 119 distribution and habitat 46, 51, 52 social organisation and behaviour 99, fossils 59 100, 127, 128, 129, 130, 131 short-tailed hopping mouse (Notomys see hopping mice amplus) 8, 21–2 stick-nest rats (Leporillus sp.) 5, 8, 19 short-tailed mice (Leggadina sp.) 5, 8,18 distribution and habitat 42, 45, 47 community structure 123 fossils 56, 57, 59 distribution and habitat 42 history 9, 10, 12, fossils 57 origin and evolution 64, 65, 68 phylogeny 63 phylogeny 63 social organisation and behaviour 132, see greater stick-nest rat 133 see lesser stick-nest rat

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stick nests 135, 136 male reproductive characteristics 92 swamp rat (Rattus lutreolus) 9, 26, 36, 86 origin and evolution 62 community structure 122, 123 parasites and disease 140 conservation 163 phylogeny 63 dentition and diet 103, 105 social organisation and behaviour 136 distribution and habitat 37, 47, 48, 49, see water rats 52–3 water rats 5, 7, 9, 33–4 female reproductive characteristics 95, origin and evolution 56, 63, 66, 70 96 see water mouse fire, response to 121 see water rat fossils 58, 59 water rat (Hydromys chrysogaster) 5, 7, 9, 33, origin and evolution 64 70, 84 parasites and disease 141, 142, 143, 144 behaviour 99 seasonal dynamics 119 conservation 149, 163 social organisation 134 dentition and diet 102, 103, 104, 106, see native Rattus 109, 110, 112 distribution and habitat 39, 42, 44, 45, testis size 88, 89, 90 46, 47, 49, 50, 51, 53, 84 tree rats (Mesembriomys sp.) 5, 8, 20 evolution 61, 65 community structure 123 female reproductive characteristics 96, conservation 161 98 diet 102 fossils 56, 57, 58 distribution and habitat 42 gastrointestinal tract 112, 113, 114 female reproductive characteristics 99 male reproductive characteristics 88, 89, origin and evolution 68 90, 92 phylogeny 64, 66 movements and home range 116 seasonal dynamics 118 parasites and disease 140, 143 social organisation and behaviour 133 seasonal dynamics 119 see black-footed tree rat skull 106 see golden-backed tree rat see water rats tropical short-tailed mouse (Leggadina western chestnut mouse (Pseudomys nanus) lakedownensis) 8, 18 8, 26, 79 conservation 158 community structure 121, 122, 123 distribution and habitat 44, 46, 49, 50 conservation 152 home range 116 dentition and diet 4, 109 origin and evolution 69 distribution and habitat 46, 50, 51, 59 social organisation and behaviour 132 female reproductive characteristics 96, see short-tailed mice 99, 100 true rats see native Rattus male reproductive characteristics 92 movements and home range 116 ‘Uromys group’ 7, 9 phylogeny 62 Uromys sp. see mosaic-tailed rats seasonal dynamics 119 Uromys caudimaculatus see giant white- social organisation and behaviour 129 tailed rat western mouse (Pseudomys occidentalis) 9, Uromys hadrourus see masked white- 29, 81 tailed rat conservation 157 distribution and habitat 46, 51, 52 viruses 146–7 fossils 57, 58 western pebble-mound mouse (Pseudomys water mouse (Xeromys myoides) 7, 9, 34, 84 chapmani) 8, 27, 79 conservation 153, 157, 160, 161 distribution and habitat 50 dentition and diet 103, 104, 105, 107 social organisation and behaviour 135 distribution and habitat 44, 49 see pebble-mound mice

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white-footed rabbit rat (Conilurus albipes) Zyzomys sp. see rock-rats 8, 17 Zyzomys argurus see common rock-rat distribution and habitat 52, 53 Zyzomys maini see Arnhem Land rock-rat female reproductive characteristics 96 Zyzomys palatalis see Carpentarian fossils 58, 59 rock-rat Zyzomys pedunculatus see central rock-rat Xeromys myoides see water mouse Zyzomys woodwardi see Kimberley rock-rat

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