Project Deliverance the Response of ‘Critical-Weight-Range’ Mammals to Effective Fox Control in Mesic Forest Habitats in Far East Gippsland, Victoria

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Project Deliverance The response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria

A Victorian Government Initiative Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Department of Sustainability and Environment

Project Deliverance The response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria

A Victorian Government Initiative Publisher/Further information - Department of Sustainability and Environment, PO Box 500, East Melbourne, Victoria, Australia, 3002. Web: http://www.dse.vic.gov.au

First published 2006.

© The State of Victoria, Department of Sustainability and Environment, 2006 All rights reserved. This document is subject to the Copyright Act 1968. 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 or otherwise without the prior permission of the publisher.

ISBN 1 74152 343 5

Disclaimer—This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purpose and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.

Citation— Murray, A.J., Poore, R.N. and Dexter, N. (2006). Project Deliverance—the response of ‘critical weight range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria. Department of Sustainability and Environment, Melbourne.

Front cover photographs—Long-nosed Potoroo, DSE/McCann; Forest at Cape Conran, Andrew Murray.

Other photographs—p1 Long-nosed Potoroo, DSE/McCann; p3 Aerial view Cape Conran, DSE Orbost; p5 Banksia Woodland, Andrew Murray; p12 Bait station, Andrew Murray; p18 Red Fox, Dave Watts; p25 Long-nosed Potoroo, DSE/McCann; p39 Bandicoot tracks at Cape Conran, Martin O’Brien; p43 Banksia Woodland at Cape Conran, Andrew Murray. www.dse.vic.gov.au

ii Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Acknowledgments

The authors wish to acknowledge that this study was carried out on land traditionally owned and managed by the Gunnai-Kurnai people and the Bidawal people of far East Gippsland.

The authors would like to thank the following people and organisations for their valuable contribution and support: Brendan Edgar, formerly of the Environment Forest Taskforce within Environment Australia, for securing the funds for the first three years of the project. Rod Gowans, Ian Mansergh, Gordon Friend and Tim Clancy (Biodiversity Research Steering Committee) are thanked for ensuring that funds were made available to ensure the project could be satisfactorily concluded.

Dr. Stephen Henry (Department of Sustainability & Environment, Orbost) for his unfailing support for this study, and his editorial corrections to the final draft of this report.

Stephen Platt and Lawrence Ferns made invaluable editorial comments to the report.

‘Honey’ (Bob) Andrews was involved in the early stages of the project and helped make most of the bait stations. The numerous DSE and DPI colleagues involved in fire management, pest management and timber harvesting who were asked to modify, cease or otherwise put on hold some of their activities are acknowledged and thanked. We wish to thank Animal Control Technologies for mixing the beads and glitter into the free-feed baits. The local residents, who adjoined some of the study sites, in particular Mick Camilleri and Peter Wermke, are thanked for their interest in the project. Dr David Choquenot (formerly of the Arthur Rylah Institute for Environmental Research) provided support and encouragement. Barbara Triggs analysed scat samples, and numerous people assisted from time to time with the trapping program. Josh Puglisi, Manager of the Cape Conran cabins, has given us assistance and constant encouragement. Parks Victoria staff are thanked for their support, occasional use of equipment, and access to certain tracks. The forbearance of Larissa Murray while Andrew was based in Mallacoota trapping in the Stony Peak study site (and many other trips away) is greatly appreciated.

Thanks to Dr Roger Pech, CSIRO Sustainable Ecosystems, Canberra ACT; Dr Glen Saunders, NSW Dept of Primary Industries, Vertebrate Pest Research Unit, Orange NSW; and Dr Graham Mitchell, Foursight Associates, and DSE Chief Scientist for reviewing the manuscript.

Funding for this publication was provided by the Weeds and Pests on Public Land Including National Parks Initiative.

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria iii Contents Acknowledgments iii

Table of Contents iv

Summary 1

Section 1: Introduction 3

Objectives 3

Report structure 4

Known benefits of fox baiting 4

Developing a fox baiting strategy suitable for Victoria 4

Section 2: The Study Sites 5

Selection of paired baiting areas 5

The West Coast study site 6

The East Coast study site 8

The Stony Peak study site 9

Previous CWR mammal and fox surveys 11

Section 3: Baiting Strategy Design 12

Methods 13

Establishing bait stations 13

Baiting with non-toxic baits impregnated with indicator beads/glitter 14

Scat analysis 15

Results 15

Discussion 16

Area of effect and distance between bait stations 16

Untested variables 16

Conclusions 17

Section 4: Implementation of Poison Baiting 18

Methods 18

Results 19

West Coast study site 19

East Coast study site 19

Stony Peak study site 19

iv Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Discussion 23

West Coast study site 23

East Coast study site 23

Stony Peak study site 23

Increase in bait-take over time 23

Bait-take as an indicator of success 24

Conclusions 24

Section 5: Monitoring the Response of Medium-sized Mammals 25

Critical Weight Range mammals 25

Species and their conservation status 26

Rate of increase in mammal populations 26

Methods 27

Design 27

Cage-trapping 27

Analysis of data 27

Rainfall 27

Results 28

Individual population response 28

Analysis of results 34

Rainfall data 37

Section 6: Discussion and Conclusions 39

Comparison to other studies 39

Responders – Long-nosed Potoroo & Southern Brown Bandicoot 39

Mixed response – Long-nosed Bandicoot 40

Mixed response – Common Brushtail Possum 41

Insignificant response – Common Ringtail Possum 41

Overall variability and habitat 41

Site variability 41

Conclusions 42

Appendix 1: Habitat complexity as a determinant of mammal populations 43

References 47

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria List of Figures Figure 1: Location of study sites 6

Figure 2: Layout of the West Coast study site, indicating the locations of the bait stations and the trapping transect in the treatment area and non-treatment area 7

Figure 3: Layout of the East Coast study site, indicating the locations of bait stations and the trapping transect in the treatment area and non-treatment area 8

Figure 4: Layout of the Stony Peak study site, indicating the locations of the bait stations and the trapping transect in the treatment area and non-treatment area 10

Figure 5: Diagrammatic cross-sectional view of a bait station as used in this study 14

Figure 6: The distance travelled from the bait station of presumed origin to the point of deposition 16

Figure 7: Bait-take in the West Coast non-treatment area 20

Figure 8: Bait-take in the West Coast treatment area 20

Figure 9: Bait-take in the East Coast non-treatment area 21

Figure 10: Bait-take in the East Coast treatment area 21

Figure 11: Bait-take in the Stony Peak non-treatment area 22

Figure 12: Bait-take in the Stony Peak treatment area 22

Figure 13: Trap success of all CWR species in the West Coast study site expressed as a percentage 30

Figure 14: Trap success of all CWR species in the East Coast study site expressed as a percentage 30

Figure 15: Trap success of all CWR species in the Stony Peak study site expressed as a percentage 31

Figure 16: Total captures per trap night (CPT-1) for Southern Brown Bandicoot 31

Figure 17: Total captures per trap night for Long-nosed Bandicoot 32

Figure 18: Total captures per trap night for Long-nosed Potoroo 32

Figure 19: Total captures per trap night for Common Brushtail Possum 33

Figure 20: Total captures per trap night for Common Ringtail Possum 33

Figure 21: Total captures per trap night for all mammals 33

Figure 22: Long-nosed Potoroos known-to-be-alive in the East Coast study site 34

Figure 23: Rainfall anomalies for Victoria from the 1st of April 1999 until the 31st of March 2002 37

Figure 24: Habitat Complexity Scores for trap sites located in the West Coast study site 45

Figure 25: Habitat Complexity Scores for trap sites located in the East Coast study site 45

Figure 26: Habitat Complexity Scores for trap sites located in the Stony Peak study site 46

vi Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria List of Tables Table 1: General characteristics of the three study sites used in this project 6

Table 2: Average distances between bait stations established in each of the study sites 13

Table 3: The number of bait stations established in each study site 14

Table 4: The number of fox scats collected and the number that contained beads and/or glitter at each treatment and non-treatment area 15

Table 5: West Coast study site - total captures of individuals during each trapping session 28

Table 6: East Coast study site - total captures of individuals during each trapping session 29

Table 7: Stony Peak study site - total captures of individuals during each trapping session 29

Table 8: General linear mixed model for mammal species 35

Table 9: Rainfall anomaly figures for far East Gippsland for consecutive 36-month periods. 38

Table 10: Visual method for scoring complexity of the habitat at trap sites 44

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria vii Summary

This report details the results of ‘Project Deliverance’ — a project designed to determine the response of native mammals living in forest ecosystems in south-eastern Australia to an ongoing effective baiting program undertaken to reduce the population of the introduced Red Fox (Vulpes vulpes). Project Deliverance was conducted between 1998 and 2003 and was the precursor to the development of a broader regional fox control program launched in 2004, known as ‘Southern Ark’.

Project Deliverance had two main ecological management objectives:

• To develop and implement a baiting strategy to effectively reduce the abundance of foxes in large areas of native forests.

• To assess changes in abundance (if any) of native mammals species at risk from fox predation.

Baiting strategy design From an operational perspective, the design of the baiting strategy needed to be cost-effective and logistically feasible to be applied to managing very large areas of land. The design involved the establishment of permanent bait stations at approximately 1km intervals alongside vehicle tracks within the area of management interest. In this way, deployment of the bait station could be readily conducted from a suitable vehicle, and easily located on subsequent visits. The baits used were designed specifically for foxes, and buried so that they would not be accessible to native animals, thereby minimising risks of non-target impacts.

The baiting trials were conducted in forest ecosystems along the coastal foothills of East Gippsland, Victoria. Three geographically distinct study sites varying in size were selected and named the ‘West Coast’, ‘East Coast’ and ‘Stony Peak’ study sites. Each of the three study sites supported a range of different native forest types, as defined by Victoria’s Ecological Vegetation Class (EVC) mapping protocol.

1 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria A pair of baiting areas (‘treatment’ and ‘non-treatment’), varying in size between 7-14000ha, were identified within each study site, which featured identical EVCs and had been subjected to similar historical land management practices. Toxic baits were only buried within treatment areas while non-toxic baits were buried in the non-treatment areas to provide an objective comparison. Both toxic and non-toxic baits were replaced every four weeks across all study sites over a period of four years.

Reduction of red foxes The rate at which baits were taken (‘bait-take’) from the permanent bait stations was compared before and after the addition of toxic baits at both the treatment and non-treatment areas. This was used as an indirect measure of fox abundance. A relatively high level of bait-take occurred at both the treatment and non-treatment areas prior to the addition of toxin. There was generally a rapid decline in the level of bait take following the addition of toxin at the treatment areas. Overall, the conclusion was that the fox toxin, the bait station design, and the intensity and frequency of baiting was successful at reducing the abundance of foxes.

Changes in small native mammal species abundance Native mammal species were chosen for measuring changes in abundance (if any) through time as a basis for assessing the ecological outcomes of reducing fox predation. Species known to be predated upon by foxes that inhabit the region were forest-dwelling marsupials such as the Southern Brown Bandicoot (Isoodon obesulus), Long-nosed Bandicoot (Perameles nasuta), Long-nosed Potoroo (Potorous tridactylus), Common Brushtail Possum (Trichosurus vulpecula), Common Ringtail Possum (Pseudocheirus peregrinus) and Mountain Brushtail Possum (Trichosurus caninus). A treadle-style cage trap was chosen as a pragmatic sampling unit as it is capable of capturing a broad range of small to medium-sized mammal species.

Sampling involved the deployment of 60 cage traps aligned in non-linear transects at 300m intervals through both ‘treatment’ and ‘non-treatment’ areas. The cages were monitored on 14 separate trapping sessions during the baiting trial, with the first two sessions conducted prior to the introduction of toxic baits.

Overall, the results for capture rates of most species could only be analysed at the East Coast and Stony Peak study sites as there was insufficient data obtained from the West Coast study site. Data for the Common Ringtail Possum did not indicate an appreciable change in abundance and there was insufficient data obtained from all study sites to analyse the response in populations of the Mountain Brushtail Possum. The results from the East Coast and Stony Peak study sites indicated an appreciable increase in the abundance of Long-nosed Potoroos and Southern Brown Bandicoots in the ‘treatment’ areas. The Long-nosed Potoroo and Southern Brown Bandicoot are two species that have historically suffered the greatest decline in range and abundance across East Gippsland. They are also the species considered to be at the greatest conservation risk from fox predation.

Data from all three study sites were grouped together to analyse abundance trends for Common Brushtail Possums and Long-nosed Bandicoots. Data for Common Brushtail Possums did not indicate an appreciable change in abundance, while that for Long-nosed Bandicoots indicated an appreciable decline in abundance. It is plausible that the decline may have been caused by a prolonged period of below-average rainfall prior to, and during, the course of the project.

The observed increase in abundance for Long-nosed Potoroo and Southern Brown Bandicoot was, however, very encouraging, and provided evidence that the baiting strategy could deliver successful ecological management outcomes for Victoria’s native mammals. The authors regard the implementation of ongoing fox control across large areas of forest as a major opportunity to improve the conservation outcomes of forest-dwelling mammalian fauna, and potentially other species preyed on by foxes, in south- eastern Australia.

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 2 Section 1

Introduction

The Red Fox is an introduced carnivore that has had a profound negative impact on the abundance and distribution of Australia’s native mammals (Burbidge and McKenzie 1989, Saunders et al 1995, Kinnear et al. 2002).

Objectives The project had two main ecological management objectives:

• To develop and assess if an ongoing, low-intensity baiting strategy could reduce the abundance of Red Foxes in large areas of native forests.

• To assess changes in abundance (if any) of native mammals species.

From an operational perspective, the design needed to be cost-effective and logistically feasible to be applied to managing very large areas of land.

3 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Report structure This report contains six main sections:

Section 1 provides the introduction to the study by outlining the objectives and an overview of the fox baiting strategy design.

Section 2 provides an ecological description of the study sites chosen in East Gippsland and other natural resource management characteristics.

Section 3 describes the design of the baiting strategy and assesses the suitability of using buried bait stations.

Section 4 describes the implementation of the baiting strategy and results that show appreciable decline of foxes following introduction of poison baits.

Section 5 describes the deployment of cage traps to sample the abundance of six target species following the implementation of baiting.

Section 6 includes a discussion of the results and conclusions.

Nomenclature in this report follows Strahan (1995).

Known benefits of fox baiting Research undertaken in Western Australia has demonstrated that reducing fox numbers has a beneficial effect on a wide range of native mammals, including rock-wallabies, numbats, bettongs and quolls (Kinnear et al. 1988; Friend 1990; Morris 1992; Morris et al. 1995; Kinnear et al. 2002).

Collectively, these species form part of a suite of mammals known as ‘Critical Weight Range’ (CWR) mammals (Burbidge and McKenzie 1989). This group of mammals are those species that weigh between 35g to 5500g, which have been shown to be at particular risk of extinction as a result of predation by introduced predators such as foxes. Victorian CWR ground-dwelling mammal species include potoroos and bandicoots. Semi-arboreal species include the Common and Mountain Brushtail Possum and Common Ringtail Possum.

Developing a fox baiting strategy suitable for Victoria In Western Australia, broad-scale fox control is achieved in areas exceeding 20000ha by aerial baiting with dried meat baits poisoned with sodium fluoroacetate (compound 1080 ‘ten eighty’; de Tores 1994). This method of baiting can be undertaken in Western Australia with minimal impact on the native mammal fauna because the assemblages of mammals have evolved in the presence of a number of plant genera (most notably shrubs of the genus Gastrolobium) that naturally contain high concentrations of 1080.

In eastern Australia, high concentrations of 1080 do not naturally occur in the environment and thus native animals have a low tolerance to it (King 1990). The use of specifically constructed and precisely located bait stations, within which baits are buried, enabled the baiting effort to target Red Foxes while at the same time minimising non-target consumption of baits (e.g. by Spotted-tailed Quolls Dasyurus maculatus). The approach of using bait stations that consist of tilled and aerated sandy substrate also ensures that footprints of the species visiting the bait stations and extracting baits can be identified during regular checks. This ensures that the removal of poison baits by animals is effectively monitored, and steps taken to ensure that non-target visits to bait stations are minimised.

The first component of this project was to develop a bait delivery method suitable for Victorian ecosystems, based on the techniques available. The report details how commercially available Foxoff® Econobaits containing 1080 were used. These baits could be buried in the soil of constructed bait stations and readily located by foxes for consumption. However, importantly, because the baits are buried at depth within the bait station, they are not readily located and consumed by native carnivores so they pose minimal risk to non-target species. The report also investigates the cost-effectiveness of deploying baits at 1km intervals to assess if adequate consumption rates could be achieved by using minimal baiting resources.

The second component of the project concerned trialing the implementation of the baiting strategy within three representative forest ecosystems of far East Gippsland. The report provides a bio-geographic overview of each forest ecosystem chosen as the study sites for implementing the trial. For each study site, a pair of 'treatment' and 'non-treatment' baiting areas were assigned. Poison baits were only deployed within 'treatment' baiting areas. This provided an objective comparison of the effect of poison baits on the abundance of foxes and provided a basis for assessing the ecological outcomes of reducing fox numbers by concurrently tracking changes in the abundance (if any) of medium-sized native animals.

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 4 Section 2

The Study Sites

Three study sites (Figure 1) representing forest ecosystems of coastal and foothill landscapes of far East Gippsland were selected for the project. The study sites chosen were named the ‘West Coast’ (comprising the Tildesley and Hartland Forest Management Blocks), the ‘East Coast’ (comprising the Yeerung Forest Management Block) and the ‘Stony Peak’ (comprising East Wingan and Stony Peak Forest Management Blocks). The major Ecological Vegetation Classes (EVC) found in each set of study sites are listed in Table 1.

Selection of paired baiting areas A pair of baiting areas was identified within each study site that featured similar EVCs and similar historical land management practices (e.g. logging, road construction, past predator control measures) and/or wildfire disturbance.

For each pair, a ‘treatment’ and ‘non-treatment’ area was identified. Toxic baits were buried within treatment areas, while non-toxic baits were buried in non-treatment areas. This provided an objective comparison of the effect of poison baiting on fox populations while concurrently tracking changes in the abundance (if any) of medium-sized native animals.

Habitat complexity of each pair of treatment and non-treatment baiting area, for each study site, was scored visually using the method developed by Newsome and Catling (1979). This was conducted to quantify the habitat similarity between pairs of treatment and non-treatment baiting areas. It was found that for all study sites, habitat complexity scores were similar for each pair of baiting areas, and that all pairs were suitable for supporting CWR mammals (details of methods and results for habitat complexity are presented in Appendix 1).

5 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Figure 1: Location of study sites

Cann River Mallacoota

Orbost

Marlo Stony Peak Site East Coast Site West Coast Site Treatment Non-Treatment

Table 1: General characteristics of the three study sites used in this project

Study site Ecological Vegetation Treatment area Non-treatment area Classes (EVCs)

West Coast Lowland Forest, 7,000 ha 7,000 ha Limestone Box Forest

East Coast Banksia Woodland, Wet 14,000 ha 12,070 ha Heath, Lowland Forest

Stony Peak Lowland Forest, Riparian Scrub 12,000 ha This was a linear non-treatment area that ran for approximately 35km of vehicle track – see explanation in text

The West Coast study site The West Coast study site was located in the Tildesley (treatment area) and Hartland (non-treatment area) Forest Management Blocks. These areas of forest are located between Orbost and Nowa Nowa, south of the Princes Highway (see Figures 1 and 2). The Princes Highway bordered the treatment area to the north, Bass Strait to the south, the Nowa Nowa arm of Lake Tyers to the west, and Hospital Creek to the east. The non-treatment area was located five kilometres to the east. Both treatment and non-treatment areas were approximately 7000ha in size.

Figure 2 illustrates the locations of the cage-trap transects in both the treatment area (shaded in pink) and the non-treatment area (shaded in blue). Bait stations in the West Coast treatment area (foxes poisoned) are shown in red triangle, while those in the non- treatment area (fox presence monitored) are in dark blue circle.

The topography in both treatment and non-treatment areas consists of flat to undulating terrain, with gentle slopes rising from sea level to around 80m above sea level. The slopes were steeper on the gullies within the treatment area that drain into Lake Tyers, and on the major streams that drain the study area (i.e. Hospital Creek [treatment area] and Simpson Creek and Dinner Creek [non-treatment area]). These waterways drain south into Ewing Marsh, which drains into the Snowy River estuary at its eastern end.

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 6 North of Ewing Marsh, the West Coast study site consists of Upper Pliocene terrestrial gravels and clay that is overlying Lower Pliocene and Miocene calcareous marine deposits (Newell and Woodruff 1962). The soils in the study area tend to be reddish brown or yellowish brown duplex soils in the north, becoming sandy loams and sands in the south, while Ewing Marsh consists of black peaty sands or sandy loams over impermeable clays (Newell and Woodruff 1962).

Figure 2: Layout of the West Coast study site, indicating the locations of the bait stations and the trapping transect in the treatment area and non-treatment area

I EE L HR A T P

A W W S .S E O .M V N H . E A L M E F L A A I R H R W O E A R G D T RD. W H A . A E H R A N R Y Y TL G A R N A D BO L O N G D . R P RD A . Project Deliverance A G T E BE T R R IV A ER C West Coast Site

K M O A N I N G . S D M

R . . I D

H . R HI G H W AY RD TK . RD . S R E K T E E G S R R L IN TK C

D S . O

. S O R W C A Y G A R A S N O S LI S AR T E L P P I M

R S

D Non-Treatment Site

IR . I S D H R

W Treatment Site O

. C C

K K. M

L I E R T B

T E OW W R A A C

A E W T T L

S R . T O E E

O D E M T R R B . E B L H A K T E O O T H A TO L C . S E D TA H K S R L T E . E S C O LIN K K L I

I R T V C S E L R L I D D . E A WO M B A T K B TK . T E A LE Y HU K R A L M B B V UG . RO A D SI MP S O N P P Y HA S R L D E LIN K . . S TK K R S . T D . U CA M E R O NS R AR M NO . 1 T R S D O N .

B C R R O O R O E E NN R G DI E A CA M K ER . L ON S W C K I R M NO .2 R T A R C B D O L E L A E D A O . C K M K IN H O BR T L N E A O. 1 T RM N A K Y A E S R ED D R RE S O . U A O T D BA RE H E D Y O M A R M W NO R .2 K D C . IR O A N R B T A R K S AS R TK O . M N P B R O E S T E T TK . M A W A K A N D N S A G R O M

B C H

EA K R AS S B R D EN T T K . MO R TR I D .

Legend N S

R E .

Y K

T T

B Road

G Treatment Bait station

Non-Treatment Bait station

Treatment Trapping Transect

Non-Treatment Trapping Transect

0 1 2 3 Kilometres

The climate of the West Coast study site is typical of the coastal lowlands of East Gippsland, with mild winters and warm to hot summers. Rainfall is fairly evenly distributed throughout the year. The average annual rainfall for the West Coast study site is in the range of 750-850mm.

As a result of the coastal location of the West Coast study site, the temperatures are relatively moderate. January is the warmest month (mean maximum 25.1°C, mean minimum 12.6°C), and June the coolest (mean maximum 14.5°C, mean minimum 3.8°C).

The West Coast study site has a long history of timber harvesting, particularly of species with durable timber for sleepers. Harvesting commenced in the late 1880’s and continued until the 1990’s (Featherstone 1985). Both Featherstone (1985) and McKinty (1969) considered that the overall condition of the forest in the study area to be poor, from a silvicultural perspective, though structural diversity remains high.

A large wildfire burnt the entire non-treatment area in the summer of 1971-1972 (Kemp et al. 1994), and another burnt part of the non-treatment area in 1981 (Lugg and Bartlett 1993). Most of the treatment area has been burnt at least once since 1964, which is when accurate fire records were first collected (Kemp et al. 1994). Fuel reduction burning takes place across the majority of the study

7 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria site. The frequency at which this takes places varies, with some areas burnt every three to five years in order to reduce the hazard to adjoining landholders, whereas other areas may not be burnt for several decades, with the frequency being dependent on the rate of fuel accumulation.

The major vegetation types (EVCs) that occur in the West Coast study site are Lowland Forest on the gentle slopes and flats and Limestone Box Forest in the gullies and major drainage lines. The Lowland Forest consists of an overstorey of Eucalyptus globoidea, along with E. botryoides, E. seiberi, E. cypellocarpa, and E. tricarpa. The shrub layer is variable in density and ranges from open grassy areas to areas of quite dense vegetation. Common species in the shrub layer include Epacris impressa, Pimelea humile, Persoonia linearis, Acacia terminalis, A. longifolia, and Banksia serrata. The ground layer in many parts of the study site is dominated by sedges and sedge-like plants, which are common in poorly drained plant communities (Kemp et al. 1994). In the Limestone Box Forest, the overstorey is dominated by Eucalyptus baueriana, E. globoidea and E. botryoides. In some areas E. bosistoana sometimes occurs in pure stands. The shrub layer tends to be dominated by tall to medium soft-wooded shrubs, such as Olearia lirata, Coprosma quadrifida, Indigofera australis, Cassinia longifolia and Banksia serrata. The ground layer is rich in creeping ground herbs, grasses, ferns, and sedges.

A detailed analysis of the flora of the West Coast study site can be found in Kemp et al. (1994).

The East Coast study site The East Coast study site was located in the Yeerung Forest Management Block (see Figures 1 and 3). The area is characterised by gently rolling hills and flat, poorly draining low-lying plains (Bramwell et al. 1992). The treatment area was approximately 14000ha in size, and was situated in the southern central part of this block, in the Cape Conran and Yeerung River area. The non-treatment area was located approximately 3km to the east, in the forested area to the west of Sydenham Inlet, and was approximately 12000ha in size.

Figure 3: Layout of the East Coast study site, indicating the locations of bait stations and the trapping transect in the treatment area and non-treatment area

Project Deliverance East Coast Site

Treatment Site

Non-Treatment Site

Legend N

Road

Treatment Bait station

Cape Conran Non-Treatment Bait station

Treatment Trapping Transect

Non-Treatment Trapping Transect

0 1 2 3 Kilometres

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 8 Figure 3 illustrates the locations of the cage-trap transects in both the East Coast treatment area (shaded in pink) and the non- treatment area (shaded in blue). Bait stations in the East Coast treatment area (foxes poisoned) are shown in red triangle, and those in the non-treatment area (fox presence monitored) are in dark blue circle.

The majority of soils in the study site are formed on Quaternary and Recent sands, and are of low fertility, with little structure and very low water-holding capacity. The soils present in the areas where heaths are found have a peaty sand upper horizon with peat at the water table level. In the northern part of the study site the soils formed on Tertiary deposits are mainly friable yellow or reddish duplex, having a generally low level of organic content (Bramwell et al. 1992). The A-horizon consists of yellowish-brown sand, which lies over a moderately structured yellowish-reddish brown clay layer (Bramwell et al. 1992).

The climate of the East Coast study site is similar to that of the West Coast study site, with an annual rainfall average of between 800mm and 1000mm, which is distributed evenly throughout the year. The East Coast study site is similar to the West Coast in that January is the warmest month, June is the coolest and average temperatures are similar.

While parts of the study site are burnt on a regular rotation (every few years) in order to protect private property, there are large areas of Banksia Woodland and Wet Heath that are long unburnt.

Although timber harvesting has taken place in the northern parts of Yeerung Forest Management Block, timber harvesting has not been prevalent in either the treatment or non-treatment areas.

The predominant vegetation types (EVCs) in the East Coast study site are Banksia Woodland, Wet Heath and Lowland Forest. The Banksia Woodland consists of an overstorey of Eucalyptus consideniana, E. sieberi, E. botryoides, E globoidea, and E. sp. aff. globoidea, with a small tree layer of Banksia serrata or Leptospermum trinervium. The understorey is usually shrub-rich however, on frequently burnt sites, Pteridium esculentum may predominate (Woodgate et al. 1994). Common shrubs include Ricinocarpus pinifolius, Epacris impressa, Ampera xiphoclada, Acacia terminalis, Acacia suaveolens, and Correa reflexa (Woodgate et al. 1994). The ground layer is dominated by Lepidosperma concavum (Woodgate et al. 1994). Wet Heathland tends to occur in the swales between the coastal dunes. In this vegetation type drainage is poor with the water table at or near the surface for most of the year (Woodgate et al. 1994). Xanthorrhoea resinosa, Melaleuca squarrosa, Allocasuarina paludosa and Leptospermum continentale dominate this vegetation type, which tends to be very dense. Lowland Forest is a very widespread EVC in far East Gippsland, occurring on the lowland plains and coastal hills (Woodgate et al. 1994). The overstorey is dominated by a variety of eucalypts, with Eucalyptus seiberi, E. globoidea and E. consideniana being the most widespread and common overstorey species. The shrub and ground layers tend to be dense and relatively diverse in most areas. Common shrubs include Platylobium formosum, Pultenaea scabra, Tetratheca pilosa, Epacris impressa, Dampiera stricta, Acacia myrtifolia, Hibbertia empetrifolia and Persoonia linearis (Bramwell et al. 1992).

A detailed analysis of the flora of the East Coast study site can be found in Bramwell et al. (1992).

The Stony Peak study site The ‘Stony Peak’ study site was located in the East Wingan and Stony Peak Forest Management Blocks. The Stony Peak treatment area was situated across the East Wingan and Stony Peak Forest Management Blocks (see Figures 1 and 4), and was approximately 12000ha in size.

The non-treatment area was located 3km to the south of the treatment area, and lay beside vehicle tracks that divide the Benedore and Betka Forest Management Blocks to the south from the Stony Peak, Genoa and Surprise Forest Management Blocks to the north.

Figure 4 illustrates the locations of the cage-trap transects in both the Stony Peak treatment area (shaded in pink) and the non- treatment area (shaded in blue). Bait stations in the Stony Peak treatment area (foxes poisoned) are shown in red triangle, and those in the non-treatment area (fox presence monitored) are in dark blue circle.

The topography of the Stony Peak study site is undulating to hilly, with a complex pattern of ridges and valleys (Gillespie et al. 1992). The majority of the study area is less than 150m above sea level, however parts of the study site rise to above 300m.

A range of soil types is present in the study site. Along some of the valleys running through the site Quaternary alluvial deposits occur (Land Conservation Council 1985), while extensive areas of the block are composed of Devonian granitic rocks. The key topographical features of the study site are Stony Peak, which lies at 300m elevation within the treatment area, and Genoa Peak, at over 400m, which lies just to the east of the treatment area.

The climate of the Stony Peak study site is similar to that of the other two study sites, with an annual average rainfall of just over 900mm, which is distributed evenly throughout the year with a slight peak in June (Gillespie et al. 1992). February is the warmest month and July the coolest.

9 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Figure 4: Layout of the Stony Peak study site, indicating the locations of the bait stations and the trapping transect in the treatment area and non-treatment area

Project Deliverance Stony Peak Site

Mallacoota

Treatment Site

Legend N

Non-Treatment Site Road

Treatment Bait station

Non-Treatment Bait station

Treatment Trapping Transect

Non-Treatment Trapping Transect

0 1 2 3 Kilometres

The study area has been subject to regular wildfires in the past, with large fires occurring in 1967/68 and 1982/83, both of which burnt a large part of the treatment area. Logging takes place within the treatment area, and in the forests north of the non-treatment area transect. The major commercial species in the area are Eucalyptus seiberi and E. globoidea.

The dominant vegetation type (EVC) in the Stony Peak study site is Lowland Forest, where the dominant tree species in the overstorey are Eucalyptus seiberi, E. gummifera, E. globoidea and E. consideniana. The shrub and understorey tends to be dense to very dense, and is floristically rich (Gillespie et al. 1992), with an abundance of Acacia and Proteaceous species. Common species in the shrub layer include Acacia myrtifolia, A. terminalis, A. verticillata, Epacris impressa, Hakea sericea, Banksia serrata, Persoonia linearis, P. levis and Lomatia ilicifolia. Along the tributaries, gullies and drainage lines Riparian Scrub occurs, which has an overstorey mainly of Eucalyptus ovata and E. obliqua over a dense shrub layer, where common species include Acacia longifolia, Melaleuca squarrosa, Gahnia clarkei and Leptospermum lanigerum.

A detailed analysis of the flora of the Stony Peak Forest Management Block (which constitutes the Stony Peak treatment area) can be found in Gillespie et al. (1992).

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 10 Previous CWR mammal and fox surveys Published surveys detecting CWR mammals and foxes within the vicinity of each study site occurred in the early 1990’s. Sampling methods employed have involved cage traps, Elliott traps, hairtube samples, spotlight surveys and analysis of predator scats.

In the West Coast study site, Kemp et al. (1994) recorded a range of CWR mammals, with semi-arboreal species more commonly encountered than terrestrial species. Species recorded included the Long-nosed Potoroo, Common Brushtail Possum, Mountain Brushtail Possum and Common Ringtail Possum. The Southern Brown Bandicoot was not recorded by Kemp et al. (1994), although the species has been recorded on the Atlas of Victoria Wildlife (Department of Sustainability and Environment). Kemp et al. (1994) made no direct mention of foxes in surveys of the West Coast study site, other than recording the collection of ten fox scats.

For the East Coast study site, Bramwell et al. (1992) recorded a range of terrestrial and semi-arboreal CWR species, with Common Ringtail Possum appearing to be encountered most commonly. Other species detected include the Southern Brown Bandicoot, Common Brushtail Possum, Long-nosed Potoroo and Long-nosed Bandicoot. Bramwell et al. (1992) stated that foxes were “infrequently recorded” in the East Coast study site.

In the Stony Peak study site, Gillespie et al. (1992) similarly recorded a range of terrestrial and semi-arboreal CWR species, with Common Ringtail Possum encountered most commonly. Other species detected included Southern Brown Bandicoot, Long-nosed Bandicoot, Long-nosed Potoroo, Common Brushtail Possum and Mountain Brushtail Possum. Gillespie et al. (1992) believed foxes in the Stony Peak study site to be “probably common” and “widespread”.

11 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Section 3

Baiting Strategy Design

It is generally accepted that an effective way to reduce fox numbers involves the deployment of meat or meat-based baits injected or impregnated with poisons such as sodium fluoroacetate (compound 1080) (Saunders et al. 1995). A number of studies have investigated the level of uptake of baits by foxes (Fleming 1996; Fleming 1997; Thomson and Algar 2000; Thomson et al. 2000), and these have generally reported a very high uptake. A few studies (e.g. Thomson et al. 2000, Priddel and Wheeler 1997) have investigated and reported on the impact of medium to longer-term baiting programs on the fox population. A smaller number of these studies (Priddel and Wheeler 1997; Dexter and Meek 1998) report on baiting programs in which baits are buried at bait stations rather than being deployed from aircraft.

In Victoria, the only permissible form of fox and dog control using poison baits is to bury them within bait stations that are constructed on site. This is a well-established technique for predator control to protect domestic stock, especially sheep. Typically, this technique is carried out during a short period of time (several weeks), usually prior to lambing or calving. The aim is to reduce the number of foxes and dogs in the immediate vicinity until the calves or lambs are large enough to fend for themselves. Bait stations tend to be established relatively close together, with spacing varying from between 50m to 500m, and are normally placed along fence lines or alongside vehicle tracks. Bait stations have traditionally consisted of a mound of raked up soil, formed above the surface of the ground, into which the bait is placed. While this spatially intensive baiting strategy may be effective in reducing canid numbers during short periods over relatively small areas, such a design would not be economically or logistically feasible for application across large forest ecosystems. In addition to this, the standard method of bait station construction (i.e. a mound raked up above the surface of the ground) may be inappropriate in forests given the large number of potential non-target species that may consume baits if not buried deeply enough. These non-target species include Spotted-tailed Quoll, Lace Monitor, Dingo, bandicoots, potoroos, ravens and currawongs.

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 12 Previous research carried out in the Alpine National Park by Murray (1998a) had demonstrated that both dogs and foxes will readily locate and consume a commercially available bait called Foxoff® Econobait. These (unpoisoned) baits were placed in stations just below the surface of the ground and lightly covered by sand. The bait stations were checked on a weekly basis over three months. Overall, the results of Murray (1998a) suggested that establishing bait stations at distances of 400 – 500m apart resulted in considerable overlap in the ‘area of effect’ of the bait stations, and thus significant resources were found to be wasted.

Based on this earlier work in the Alpine National Park, the first component of this project was to establish if an adequate ‘area of effect’ could be established for controlling foxes by placing bait stations at larger intervals of approximately one-kilometre. If successful, resources to develop and implement the program on a wider scale (i.e. time, labour costs, number of baits) could be significantly reduced compared to established practices. Reducing the intensity in the number of baits used would also significantly minimise the risk of impact to non-target species.

Methods

Establishing bait stations A baiting program using unpoisoned baits was trialed with bait stations established at intervals of approximately 900-1000m across the three study sites. The average distance between bait stations in each study site is given in Table 2. Bait stations were established alongside the network of vehicle tracks running throughout each site. In this way, bait stations could be efficiently serviced and maintained.

Table 2: Average distances between bait stations established in each of the study sites

Average distance (m) between bait stations via track network

West Coast treatment area 874

West Coast non-treatment area 960

East Coast treatment area 945

East Coast non-treatment area 958

Stony Peak treatment area 982

Stony Peak non-treatment area 985

Each bait station consisted of an area of earth approximately one metre in diameter adjacent to the vehicle track. A hole of depth approximately 10 - 15cm was excavated. The soil was then sieved back into the hole in order to remove rocky material and vegetative matter. When required, more soil was collected from nearby to add to the bait station. This was also sieved until a mound elevated approximately 10cm above the surrounding land had been formed. This provided enough soil to bury the baits at a depth greater than 15cm, which is the recommended depth for baits to be placed to avoid non-target species such as the Spotted-tailed Quoll (Murray 1998b). Figure 5 gives a diagrammatic cross-sectional view of such a bait station. A total of 311 bait stations were established and maintained for this part of the study. The number of bait stations used in each study site is listed in Table 3.

13 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Figure 5: Diagrammatic cross-sectional view of a bait station as used in this study

12 -15 cm

100cm

Table 3: The number of bait stations established in each study site

Treatment area Non-treatment area

West Coast 62 31

East Coast 63 50

Stony Peak 71 34

Baiting with non-toxic baits impregnated with indicator beads/glitter In the centre of each bait station, one non-toxic 35g Foxoff® bait was placed at a depth of 15cm below ground level. Each bait contained one of seven different colours of plastic bead or one of five different colours of glitter, which had been added to the bait matrix during the manufacturing process. When consumed by an animal, these ‘indicator’ beads and glitter pass benignly through the digestive system and appear in the scats (faeces). Bait stations were assigned a single colour of bead or glitter, which remained for the duration of the study. In order to reduce potential confusion about the point of origin, baits containing beads of the same colour were placed in bait stations as far apart as possible.

Bait stations were checked at weekly intervals. The study was interrupted by the floods and associated severe wind storms which occurred in East Gippsland during the 23rd and 24th of June 1998. This restricted access to the study sites until the vehicle tracks were cleared of debris.

During each check, every bait station was dug over, the old bait removed (if present) and replaced with a fresh bait. A small amount of tuna oil was added as an additional lure to each bait station before the bait was buried. During each check, details concerning bait-take and any evidence of species that may have visited the bait station were recorded.

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 14 Scat analysis During each check, all canid scats found on the bait stations were collected, labelled and oven dried for a period of 52 hours at 80°C. A combination of hair analysis, odour, size and evidence at the point of collection (e.g. tracks or the smell of urine) was used to determine whether a fox had deposited the scat.

Once oven-dried, each scat was broken open and thoroughly searched for beads and glitter. When a scat was found that contained beads or glitter, it was assumed that the canid that had deposited the scat had consumed the bait from the nearest bait station that contained the relevant beads or glitter. This distance was used in calculations. The straight-line distance between the ‘bait station of presumed origin’ and the ‘bait station of deposition’ was measured on a 1:50000 scale topographic map.

Scats containing multiple colours of indicator beads or glitter were treated in the same manner as scats containing one colour of bead, in that a single straight-line measurement was calculated from the nearest relevant bait station for each colour within the scat. In this way the area of effect of bait stations was estimated, based on the distances travelled by foxes from one point (where they consumed a bait containing indicator beads/glitter) to a bait station (where they happened to defecate a scat containing indicator beads/glitter).

Scats containing beads or glitter were first collected in April 1997, and the last scat containing beads was collected in December 1999.

Results A total of 630 fox scats were collected from the West Coast, East Coast and Stony Peak study sites. Eighty-six fox scats (13.6% of all fox scats collected from bait stations) were found to contain beads and/or glitter. A further six scats that contained beads/glitter were incidentally collected from roads and included in the data set. Thirty one scats (33.7% of the scats collected that contained beads/ glitter) were found to contain more than one colour of bead/glitter, indicating that baits from multiple bait stations had been consumed over a fairly short period of time. One scat from the Stony Peak treatment area contained five different colours of indicator bead or glitter. Nineteen scats containing beads/glitter were found on the bait stations from which the baits had presumably originated. These scats are regarded as having travelled ‘zero’ distance. The number of scats collected in each study site and the number of scats that contained beads and glitter are presented in Table 4.

Table 4: The number of fox scats collected and the number that contained beads and/or glitter at each treatment and non-treatment area

Number of scats collected Number of scats containing beads and/or glitter

West Coast treatment area 173 45

West Coast non-treatment area 95 10

East Coast treatment area 81 2

East Coast non-treatment area 22 1

Stony Peak treatment area 190 22

Stony Peak non-treatment area 69 12

Total 630 92

It was possible to calculate the straight-line distances travelled for 118 collections of beads or glitter found in 92 scats. The maximum distance estimated was 3250m. The average distance travelled between point of origin and point of deposition was 1318m.

The distance travelled by foxes between bait stations, as indicated by the straight-line distance travelled by beads and glitter from one bait station (‘point of presumed origin’), to another bait station (‘point of deposition’), as a scat, is graphed in Figure 6. The total number of scats travelling a particular distance continues to accumulate steadily until approximately the 1800m point. At this point, the line of the cumulative number of scats collected begins to asymptote in shape.

15 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Figure 6: The distance travelled from the bait station of presumed origin to the point of deposition

20 140

18 Approximate Bait Station Radius Catchment 120 16

100

14 s egate egate Scat ggr 12 A 80 ch

Ea 10 In In

60 egation of 8 Aggr

. of Scats Scats of . 6 40 No

20 Cumulative 2

0 0 0 1-199 200- 400- 600- 800- 1000- 1200 1400- 1600- 1800- 2000 2200- 2400- 2600- 2800- 3000- 3200 399 599 799 999 1199 1399 1599 1799 1999 2199 2399 2599 2799 2999 3199 3399 Aggregate Distances from Bait Station of Origin to Bait Station of Deposition

Discussion

Area of effect and distance between bait stations When broad-scale fox control is contemplated as a conservation or wildlife management tool, it is imperative that the majority of foxes residing within the control area are presented with an opportunity to locate and consume poison baits. This is best achieved by ensuring that bait stations are established within the home range of the majority of individuals. An objective of effective and efficient fox control should be to kill the maximum number of foxes with the expenditure of the least amount of resources (labour, baits and time). In this study we attempted to determine if establishing and maintaining bait stations at approximately one-kilometre intervals on a network of vehicle tracks would provide a sufficient intensity of baiting to ensure that the majority of the resident foxes had the opportunity to encounter bait stations.

Figure 6 illustrates that scats with indicator beads/glitter were consistently deposited up to 1600 - 1800m from their point of presumed origin. After this distance, the number of scats containing beads/glitter begins to decline. While a small number of scats were deposited on bait stations that contained beads/glitter from baits buried as far as 3km away, it is likely that 1600m represents a reasonable area of effect for bait stations.

Establishing bait stations at one-kilometre intervals therefore provides a significant overlap in the area of effect between bait stations with a high probability of foxes encountering at least one bait station. A one-kilometre spacing represents a significant reduction in the number of baits typically used in fox control practices to protect agricultural areas. It provides a potentially effective and cost-efficient methodology for use in forest areas.

Untested variables One of the variables the study did not directly address is whether the number and orientation of available vehicle tracks within an area has an appreciable influence on the success of the control program. In forest ecosystems, foxes occupy home ranges in the order of between two and five km2 (Saunders et al. 1995). An extensive network of tracks existed across all study sites and bait stations were established at such an intensity along those vehicle tracks that it is unlikely that many fox home ranges did not overlap at least one bait station.

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 16 A second variable that this study did not address directly was the influence of forest block size on the success of the control program. Very large forest blocks without vehicle tracks running through them may have fox home ranges within them that do not encounter vehicle tracks. As baiting is conducted adjacent to vehicle tracks that are located around the perimeter of the forest block those foxes may not ever encounter bait stations. Complicating the issue is the known fact that home ranges are not fixed in time and space, and there can be considerable home range drift when populations of foxes are subject to high levels of mortality (Doncaster and Macdonald 1991).

It is not known how foxes that occupy these core territories within large forest blocks will behave once baiting commences at the perimeter. As baiting proceeds and resident foxes on the margins of the block experience a high degree of mortality, it is plausible that there would be a general drift in the fox home ranges away from the core of the block towards the perimeter. This would occur as those foxes resident at the core of the forest block seek to incorporate unoccupied forest (and therefore resources) into their home range. As these foxes shift their home range and eventually incorporate forest occupied by a bait station, it is likely that they too will eventually become poisoned. If baiting is maintained over a long enough timeframe and the trend of home range drift away from the core of the block is maintained, even very large blocks could eventually become largely depopulated of their resident foxes.

Conclusions This study has determined that placing bait stations at one-kilometre intervals creates a sufficient ‘area of effect’ to ensure that most foxes inhabiting forests in the study sites have the opportunity to encounter a bait station and be poisoned. The quantity of bait stations used in this study is approximately half the density used in current practices elsewhere. This study demonstrates how a reduction in bait stations can still be effective, thereby saving valuable resources.

Other critical prerequisites thought to be required for successful fox control programs include having a network of vehicle tracks along which bait stations can be established, baiting in an on-going fashion, and baiting a relatively large area (i.e. in the tens of thousands of hectares). Programs must be undertaken for a time period that is long enough to allow the resident foxes to locate the bait stations and must cover a large enough area to ensure that reinvasion from surrounding fox populations is minimised.

17 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Section 4

Implementation of Poison Baiting

Due to the successful results of the baiting strategy design trial described in Section 3, the poisoning component of the program commenced. The aim of this component was to reduce the fox population to a level that may allow appreciable increases in the abundance of native CWR mammals (Section 5).

Methods Using the network of bait stations described in Sections 2 and 3, unpoisoned Foxoff® baits were used initially to provide a baseline of bait consumption by foxes across the study areas. Baits were regularly replaced and free-feeding with unpoisoned baits continued until bait-take was considered to have peaked and remained relatively constant (Figures 7 - 12).

Poisoning commenced in the West Coast treatment area on 8 February 1999, in the Stony Peak treatment area on 20 April 1999 and in the East Coast treatment area on 24 May 1999. Non-poisoned baits continued to be replaced in the non-treatment areas throughout the study to provide an objective comparison.

The bait stations in each treatment area were checked every day or two during the first week of poisoning. When checking each bait station, the presence or absence of the bait was recorded as were details of the species that had removed the bait. Evidence-based techniques used to elucidate which species had taken baits included tracks, scat analysis, the odour of urine (fox urine being very distinctive) and the way the bait was excavated. All baits that were taken in the treatment areas were replaced with fresh poison baits. Once the initial poisoning program had been undertaken, and it appeared that the resident fox population had been controlled (based on the rapid decline in bait-take following the commencement of poison baiting), baiting was then undertaken mainly on a four-weekly interval. All baits were removed and replaced with fresh baits during these visits.

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 18 Results

West Coast study site Initial bait-take in the West Coast study site (Figures 7 and 8) was very high in both the treatment area and non-treatment area, with over 85% of the baits being taken at both sites during some periods. Following the commencement of the poisoning program on 8 February 1999, bait take in the treatment area dropped dramatically, until a nil bait-take was observed on 15 February 1999. About a month following this sharp decline in bait-take, bait-take began to rise, with a bait-take of up to 40% occurring for a period of about two months. From that point on until the conclusion of the project, bait-take remained low (<10%).

East Coast study site Initial bait-take in the East Coast study site was not as high as that experienced in the other study sites. In the non-treatment area, bait-take averaged around 50%, whereas the treatment area had a slightly higher bait-take at around 60% prior to poisoning (Figures 9 and 10). Following initiation of the poisoning program in the East Coast treatment area there was a sharp decline in bait-take. As in the West Coast treatment area, there was a sharp increase in bait-take in the East Coast treatment area to over 40% about a month following the initial decline, however bait-take then declined again and tended to remain below 10 - 20% compared to 40-50% in the non-treatment area. The bait-take in the treatment area ultimately declined to less than 10%.

Stony Peak study site Initial bait-take in both the Stony Peak non-treatment area (Figure 11) and treatment area (Figure 12) continued to increase until the poisoning program commenced in the treatment area in late April 1999. The pattern in the Stony Peak treatment area followed that of the West Coast treatment area, with increasing bait-take seen some time after an initial sharp decrease. Bait-take subsequently continued to rise and fall, although it tended to remain under 20%. In the non-treatment area, despite some fluctuation, the bait-take tended to remain in excess of 60%.

19 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Figure 7: Bait-take in the West Coast non-treatment area

100

Bait-take 50 ge ta en rc 40 Pe

0 8 8 8 9 9 9 9 9 9 0 0 0 0 0 0 1 1 1 1 1 1 2 2 2 2 2 2 3 6/08/9 6/10/9 6/12/9 6/02/9 6/04/9 6/06/9 6/08/9 6/10/9 6/12/9 6/02/0 6/04/0 6/06/0 6/08/0 6/10/0 6/12/0 6/02/0 6/04/0 6/06/0 6/08/0 6/10/0 6/12/0 6/02/0 6/04/0 6/06/0 6/08/0 6/10/0 6/12/0 6/02/0

Date

Figure 8: Bait-take in the West Coast treatment area

100 Poison baiting commenced (8/2/99) Area of Treatment = 7,000ha 90 Number of Bait Stations = 62

Bait-take 50 ge ta en rc 40 Pe

0 8 8 8 9 9 9 9 9 9 0 0 0 0 0 0 1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 3 8/07/9 8/09/9 8/11/9 8/01/9 8/03/9 8/05/9 8/07/9 8/09/9 8/11/9 8/01/0 8/03/0 8/05/0 8/07/0 8/09/0 8/11/0 8/01/0 8/03/0 8/05/0 8/07/0 8/09/0 8/11/0 8/01/0 8/03/0 8/05/0 8/07/0 8/09/0 8/11/0 8/01/0 8/03/0 8/05/0 8/07/0 8/09/0 8/11/0

Date

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 20 Figure 9: Bait-take in the East Coast non-treatment area

100

Area of Treatment = 12,000ha 90 Number of Bait Stations = 37- 50 80

70 e 60

Bait-atk 50 ge ta en

rc 40 Pe

0 20/08/98 20/10/98 20/12/98 20/02/99 20/04/99 20/06/99 20/08/99 20/10/99 20/12/99 20/02/00 20/04/00 20/06/00 20/08/00 20/10/00 20/12/00 20/02/01 20/04/01 20/06/01 20/08/01 20/10/01 20/12/01 20/02/02 20/04/02 20/06/02 20/08/02 20/10/02 Date

Figure 10: Bait-take in the East Coast treatment area

100

Area of Treatment = 14,000ha 90 Number of Bait Stations = 63

80 Poison baiting commenced (24/5/99)

70 e 60 -tak

rcentage Bait 40 Pe

0 14/08/98 14/10/98 14/12/98 14/02/99 14/04/99 14/06/99 14/08/99 14/10/99 14/12/99 14/02/00 14/04/00 14/06/00 14/08/00 14/10/00 14/12/00 14/02/01 14/04/01 14/06/01 14/08/01 14/10/01 14/12/01 14/02/02 14/04/02 14/06/02 14/08/02 14/10/02 14/12/02 14/02/03 14/04/03 14/06/03 14/08/03 14/10/03 Date

21 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Figure 11: Bait-take in the Stony Peak non-treatment area

100

Area of Treatment = N/A 90 Number of Bait Stations = 34

70 e 60 t-tak bai 50 ge ta en

rc 40 Pe

0 2/02/99 2/04/99 2/06/99 2/08/99 2/10/99 2/12/99 2/02/00 2/04/00 2/06/00 2/08/00 2/10/00 2/12/00 2/02/01 2/04/01 2/06/01 2/08/01 2/10/01 2/12/01 2/02/02 2/04/02 2/06/02 2/08/02 2/10/02 2/12/02

Date

Figure 12: Bait-take in the Stony Peak treatment area

100 Poison baiting commenced (24/5/99) Area of Treatment = 12,000ha 90 Number of Bait Stations = 71

Bait-take 50 ge ta en rc 40 Pe

0 9 9 9 9 9 9 0 0 0 0 0 0 1 1 1 1 1 1 2 2 2 2 2 2 3 3 3 3 3 2/02/9 2/04/9 2/06/9 2/08/9 2/10/9 2/12/9 2/02/0 2/04/0 2/06/0 2/08/0 2/10/0 2/12/0 2/02/0 2/04/0 2/06/0 2/08/0 2/10/0 2/12/0 2/02/0 2/04/0 2/06/0 2/08/0 2/10/0 2/12/0 2/02/0 2/04/0 2/06/0 2/08/0 2/10/0

Date

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 22 Discussion In each of the treatment areas, bait-take declined rapidly following the implementation of the poison baiting component of the program. This is interpreted as representing a decline in the resident fox population as those foxes that were visiting bait stations consumed baits and died. Generally, in all treatment areas the bait-take declined quickly and remained markedly lower once the poison baiting component commenced, while in the non-treatment areas the bait-take remained relatively stable and at a higher level.

West Coast study site The most significant, protracted decline in bait-take took place in the West Coast treatment area. It is postulated that this may be due to the geographic features of the site that restrict reinvasion by foxes. The site is coastal, with Bass Strait lying to the south. Another relatively broad water body, the Nowa Nowa Arm of Lake Tyers, lies to the west, which is likely to restrict fox immigration to some degree. Hospital Creek forms the eastern boundary and the Princes Highway forms the northern boundary of the site. These features may have some effect on fox dispersal.

East Coast study site Bait-take in the East Coast treatment area never reached the high levels achieved in the West Coast study site. The prevalence of the paralysis tick (Ixodes holocyclus) in heathlands and woodlands may account for a lower fox population. Short (1998) suggested the presence of I. holocyclus might have resulted in reduced fox numbers in coastal areas in New South Wales. He argued that this was one reason why rat-kangaroos (in the Family Potoroidae) persisted for far longer on the central coast of New South Wales than those on the Central Tablelands or Central-western Slopes of New South Wales. Apart from Bass Strait to the south, there are no natural features in the East Coast treatment area that would prevent or reduce reinvasion by foxes. The relatively high level of bait-take in the treatment area is probably because nearly half of the stations (28 of 63) were located adjacent to mosaics of cleared pastoral land and stands of native vegetation. Saunders et al. (1995) state that foxes are probably most abundant in fragmented environments, such as those found in agricultural landscapes, as these areas offer a wide variety of cover, food and den sites. The pattern of bait-take in the East Coast treatment area would appear to support this conclusion.

Stony Peak study site Bait-take in the Stony Peak treatment area declined dramatically following the commencement of the poisoning program and remained comparatively low. The fact that there are no obvious natural features that would prevent or reduce fox immigration into the treatment area could account for bait-take not remaining at the very low level experienced at the West Coast treatment area.

Increase in bait-take over time The extended period of free-feeding (i.e. using unpoisoned baits) in each treatment area is likely to have established a feeding pattern amongst resident foxes. With such a feeding pattern established, the rapid decline in bait-take in each of the treatment areas following the commencement of poisoning is not surprising. The slight increase in the bait-take in each treatment area following the rapid decline is noteworthy. Three possible explanations for this are proposed. Firstly, it may be due to subordinate foxes residing within the treatment areas securing access to bait stations in the absence of more dominant animals. Secondly, it may be due to young foxes immigrating into the area, encountering the bait stations and consuming baits. Finally, it may be as a result of some degree of home range drift by foxes that subsequently incorporate poisoned bait stations into their area of occupancy. Few studies have examined this aspect of fox behaviour. Doncaster and Macdonald (1991) studied a population of foxes in the city of Oxford (England), and compared it to a population in the nearby suburbs. They found that foxes in both areas occupied exclusive territories but while those in the suburbs remained spatially stable those in the city drifted in location continually. They found that city home ranges drifted at a rate equivalent to the complete displacement of an average city fox home range (38.8 ha) every 13 months. The authors attributed the drifting territories experienced in the city fox population to the higher turnover of the population (due to road mortality, construction and demolition activities) and the lower proportion of barren vixens. A similar behavioural response to that observed by Doncaster and Macdonald (1991) may be expected in this study in the areas of forest surrounding each treatment area following the implementation of fox control.

23 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria The bait-take graphs suggest that resident foxes in each of the treatment areas were poisoned, creating large vacant areas into which foxes living immediately adjacent could either shift or expand their ranges. Presumably these foxes would also eventually encounter a bait station, consume a bait and die, and the process continue. It is interesting to consider how profound this effect might be outside the area within which baits are laid, especially when one considers the prolonged period during which fox control has been carried out (nearly three years). Given a scenario of continuous home range drift in fox populations under high levels of mortality, it is possible that the fox population in areas of land adjacent to the area of land under fox control is below the fox carrying capacity for the area. Whether this ‘halo effect’ is a reality, how far away it is experienced from the area under control, and what impact it has on reducing the predation pressure on native wildlife, is worthy of investigation.

Bait-take as an indicator of success In this project the level of bait-take, or more specifically the decline in the level of bait-take following the commencement of poisoning, was used as an indicator of the success of the poisoning program. The relatively high level of bait-take experienced across the majority of the treatment areas indicated that foxes were present on all sites and abundant on the West Coast and Stony Peak treatment areas. The rapid decline in the level of bait-take across all treatment areas following the commencement of poisoning suggests that the program successfully reduced the fox population. This conclusion is based on the assumption that the majority of foxes are prepared to visit bait stations and excavate and consume baits.

There is some debate as to the appropriateness of using the level of bait-take as an index of fox presence, and the decline of bait-take as an index of the success of a baiting program. As the project was relying on an ‘active’ index, in which a lure (food) was used to attract foxes to bait stations, we are unable to determine what proportion of the fox population does not visit bait stations or consume baits. ‘Passive’ indices used to determine relative fox abundance include the use of footprints on sand pads laid across vehicle tracks, or the collection of scats from transects which are usually established along linear features such as roads. Macdonald (1976) considered that the behaviour of caching food was “an important part of their everyday life”, and so presumably is the retrieval of cached food, which is what buried baits effectively represent. It is reasonable to assume then, that if the caching and retrieval of food is such a fundamental part of the foraging ecology of the Red Fox, only a relatively small percentage of the fox population would not visit bait stations and consume baits. This is especially the case given the relatively long free-feeding period that was carried out prior to the poisoning program being initiated, during which time any neophobia displayed towards the bait stations by foxes is likely to have waned.

Conclusions The implementation of the poisoning component of the program was successful at reducing resident fox populations based on the decline of bait-take once poisoning commenced. The relatively low level of bait-take that was maintained as the project continued is interpreted as evidence that foxes that attempted to reoccupy the treatment areas also encountered bait stations and were poisoned. Thus, resupplying poison baits to bait stations throughout the year appears to be important if the program is to be successful in preventing foxes from re-establishing home ranges within treatment areas.

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 24 Section 5

Monitoring the Response of Medium-sized Mammals

This component of the project examined the impact of fox predation on medium-sized forest marsupials by measuring changes in abundance (if any) between three treatment areas where foxes were regularly controlled by poison baiting and three corresponding non-treatment areas, where foxes were not controlled by poison baiting (Section 4).

Critical Weight Range mammals In Australia, native terrestrial and semi-arboreal mammal species that weigh between 35g and 5500g are thought to be at most risk from fox predation (Burbidge and McKenzie 1989). These mammals have been termed ‘Critical Weight Range’ (CWR) species. Numerous authors make mention of the impact that foxes have had on these mammals (e.g. Kinnear et al. 1988, Burbidge and McKenzie 1989, Dickman 1996, Short 1998, Kinnear et al. 2002). A number of studies have been published to support the argument that a reduction in fox numbers is beneficial for CWR mammals (e.g. Friend, J.A. 1990; Kinnear et al. 2002; Morris et al. 2003).

The extensive eucalyptus forests of East Gippsland in far eastern Victoria are one of the last strongholds of a number of CWR mammals that have declined in abundance and distribution throughout the rest of their former range in south-eastern Australia. These species are the Long-nosed Bandicoot (Perameles nasuta), the Southern Brown Bandicoot (Isoodon obesulus), the Long-footed Potoroo (Potorous longipes) and the Long-nosed Potoroo (Potorous tridactylus). However, even in East Gippsland these species occur in chronically low abundance and are rarely captured (Henry and Murray 1993). There are also two species of largely arboreal mammal, the Common Ringtail Possum (Pseudocheirus peregrinus) and the Common Brushtail Possum (Trichosurus vulpecula), that are believed to have declined because of fox predation in other parts of their range (Saunders et al. 1995). The Mountain Brushtail Possum (Trichosurus caninus) inhabits wetter forest types, and does not often occur sympatrically with Common Brushtail Possums. Besides foxes, other species prey upon CWR mammal species in East Gippsland. These include Wild Dog and Dingo (Canis familiaris and Canis lupus dingo), Feral Cat (Felis catus), Spotted-tailed Quoll (Dasyurus maculatus), Powerful Owl (Ninox strenua), Masked Owl (Tyto novaehollandiae), Sooty Owl (Tyto tenebricosa), Lace Monitor (Varanus varius) and Diamond Python (Morelia spilota).

25 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Species and their conservation status The conservation status of CWR mammals that inhabit forest ecosystems of the three study sites varies considerably. The Southern Brown Bandicoot has declined throughout most of its range in south-eastern and south-western Australia and the relevant subspecies Isoodon obesulus obesulus is listed as Endangered under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC 1999). The Long-nosed Potoroo has also declined throughout its range in south-eastern Australia and the relevant subspecies Potorous tridactylus tridactylus is listed as Vulnerable (EPBC 1999). The Long-footed Potoroo (Potorous longipes) is listed as Endangered (EPBC 1999), and although there has been some evidence of the species’ existence in south-eastern New South Wales, live specimens and intact remains have only ever been recorded in Victoria. The Long-nosed Bandicoot (Perameles nasuta) is regarded as relatively common throughout much of its range although a number of populations have become extinct (Scott et al. 1999). It is rarely captured or recorded during surveys targeting mammals in Victoria. However, in other areas where fox control has been implemented for a number of years, such as Booderee National Park in New South Wales, they are frequently captured and recaptured (Dexter unpubl. data). The Common Brushtail Possum and Common Ringtail Possum are also regarded as common species in the forested areas of eastern Australia. The Common Brushtail Possum has, however, declined throughout most of the arid inland of Australia (Kerle et al. 1992). In Western Australia, the Western Ringtail Possum (Pseudocheirus occidentalis) has similarly declined to a fraction of its former range in forests and woodlands (Jones et al. 1994). The Mountain Brushtail Possum is not regarded as being currently at risk as a result of predation by foxes, but foxes are known to prey on the species.

Rate of increase in mammal populations If predation by foxes alone is limiting a population below the carrying capacity of the environment, then release from predation pressure should see an increase in the number of individuals in a population. If the predation pressure is reduced dramatically, then the increase should be close to the maximum rate of increase (rm) (Caughley 1977). An alternative possibility is that the species’ observed rate of increase (r) would be positive but less than rm, indicating that fox predation is negatively affecting abundance but other factors are constraining population growth. In this study the r for each species in individual study sites was calculated and compared with a theoretical rm calculated from life history parameters. A species’ rm will be made up of a number of life history parameters including diet, body mass, duration of gestation and lactation, age of first reproduction, litter size, litters per year and age of last reproduction (Thompson 1987).

The species examined in this study represent a diverse range of life history strategies and are comparable only in that they have a roughly similar body size and spend part of their time foraging on the ground. The potoroo and bandicoots are ground foragers consuming varying proportions of the sporocarps of hypogeal fungi in their diet (Claridge et al. 1993). The Long-nosed Potoroo has a long gestation period for a marsupial, produces single young and provides extended parental care (Seebeck and Rose 1988). Conversely, both species of bandicoots produce litters of one to seven and have an extremely short gestation period, reduced parental care and are relatively short-lived (Gordon and Hulbert 1989). The possums are primarily arboreal, feeding in the canopy on eucalypt foliage but also foraging in lower vegetation strata and on the ground, with the Common Brushtail Possum being more omnivorous than the Common Ringtail Possum (Pahl 1987). Both Common and Mountain Brushtail Possums are long-lived, produce a single offspring per year and provide extended parental care, while the Common Ringtail Possum can produce two litters of up to three young per year (Green 1984; How et al. 1984). Thus, if predation by foxes alone is limiting population size, then the two species of bandicoot should increase most rapidly followed by the Common Ringtail Possum with the Brushtail Possums and Long-nosed Potoroo increasing most slowly.

Thompson (1987) used the parameters — potential mean age of females producing first young, potential annual birth rate of female young, and potential mean age of females producing their final young — to calculate a theoretical rm for a range of mammal species including those species examined in this study. In Thompson’s study, an estimated rm of 4.183 for the Long-nosed Bandicoot, 3.45 for the Northern Brown Bandicoot (Isoodon macrourus) (an ecological homologue of the Southern Brown Bandicoot), 0.878 for the Common Ringtail Possum and 0.667 for the Common Brushtail Possum was calculated. A rm of 0.254 was calculated for the Mountain Brushtail Possum, and a rm of 1.058 was calculated for Long-nosed Potoroos (Thompson 1987). Thus, based on Thompson’s results, if predation by foxes alone is limiting population size then the two species of bandicoot should increase most rapidly followed by the Long-nosed Potoroo and Common Ringtail Possum, with the Common Brushtail Possum and Mountain Brushtail Possum populations increasing most slowly.

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 26 Methods

Design The location and design of cage trapping transects for this component of the project is described in Section 2. Diagrammatic representation of cage trapping transects is presented in Figures 2 to 4.

Cage-trapping In each of the three study sites, an 18km transect of 60 wire treadle-type cage traps (60cm long x 30cm high x 30cm wide) was established in each treatment and non-treatment area. Roads within the core of each site were used for the transect, with traps being placed at 300m intervals along the road at a distance of between 20 and 50m perpendicular to the road in to the forest. In total, 360 cage traps were placed in the field for the duration of the study.

Two trapping sessions were undertaken at each study site prior to any fox control being carried out. These sessions were carried out during the summer of late 1997 and autumn of 1998. Following the commencement of poison baiting, 12 trapping sessions were carried out in each of the study sites between July 1999 and May 2003.

Cage traps were baited with a mixture of rolled oats, peanut butter and golden syrup, placed within a double-spoon tea infuser to protect the bait from being consumed by non-target species such as rats. Each cage trap was covered with black polythene plastic to protect any captured animals from inclement weather. Trapping sessions were generally carried out over six or seven nights depending on weather conditions.

During a trapping session traps were checked each morning and captured animals were identified to species level, weighed, sexed, and micro-chipped. Each animal was released at the point of capture as soon as it had been processed.

Analysis of data The number of individuals of each species captured in each trapping session was used to analyse the response of the species to reduced fox numbers as a result of poison baiting. Before analysis, the data were converted to a capture rate per trap night to account for minor variations in the duration of trapping sessions. The capture rates for all species combined were analysed in a general linear mixed model. The SPSS1 program was used and mixed models option with a covariance structure selected for the repeated measure on the basis of the highest information criteria. Study sites (East Coast, West Coast, Stony Peak) and treatment (baiting/no-baiting) were entered as fixed factors with trapping session (1 to 14) entered as a repeated measure, and trapping session by treatment entered as an interactive term. This approach had the benefit of allowing analysis of samples collected at uneven time intervals that is invalid in traditional repeated measure ANOVAs and allows the selection of a covariance structure that better fits the data (von Ende 2001). The analysis was repeated for each of the five species for which their were sufficient data to analyse — Long-nosed Potoroo, Southern Brown Bandicoot, Long-nosed Bandicoot, Common Brushtail Possum and Common Ringtail Possum. Only two study sites (East Coast and Stony Peak) were analysed for the Southern Brown Bandicoot and Long-nosed Potoroo because of nil captures in the West Coast study site of the Southern Brown Bandicoot, and no captures in the West Coast non-treatment area of Long-nosed Potoroo.

A reduction in predation is likely to result in increased survivorship amongst CWR mammals in the treatment areas. To create an index of survivorship the maximum length of time between recaptures was calculated for all animals caught over more than one trapping session. For those species for which their was sufficient data, maximum recapture intervals for non-treatment and treatment areas were pooled between study sites and compared by one-tailed t-test, which excludes the hypothesis that fox control could lead to increased maximum recapture time (Rice and Gaines 1994).

Rainfall To examine whether rainfall had any additive effect on the population dynamics of the mammal species surveyed, rainfall anomaly data for consecutive 36-month periods were reviewed from the commencement of poison baiting (February 1999) until the conclusion of the project in June 2003 (Table 9, page 38).

1 Statistical Package for the Social Sciences http://www.spss.com/

27 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Results The total captures made of each species in each treatment and non-treatment area during the 14 trapping sessions are listed in Tables 5 to 7. The total trap success (expressed as a percentage) of all CWR species in each treatment area and corresponding non-treatment area over the 14 trapping sessions is graphed in Figures 13 to 15. The captures per trapnight for Southern Brown Bandicoot, Long- nosed Bandicoot, Long-nosed Potoroo, Common Brushtail Possum and Common Ringtail Possum are presented in Figures 16 to 20 respectively. Figure 21 illustrates the total captures per trapnight for all mammals combined.

The Long-nosed Potoroo (at the East Coast study site) was the only species where individuals were recaptured with enough frequency to generate a known-to-be-alive table. Figure 22 illustrates the potoroos that were known-to-be-alive in both East Coast treatment and non-treatment areas. No potoroos were captured in the non-treatment area until Trapping Session 9. Very few potoroos were known- to-be-alive in the treatment area until Trapping Session 6, after which their numbers increased until Session 12. An ecological burn was carried out during May 2002 in an area thought to be inhabited by some of the potoroos regularly trapped in the East Coast treatment area, which may account for the slight fall in numbers in Trapping Sessions 13 and 14.

Individual population response In order to examine the response of individual mammal populations in individual study sites and compare observed rate of increase with the hypothetical rm at which these species could respond, the observed rate of increase for each species at each site was calculated as the slope of a linear regression of loge abundance transformed by adding one (to account for capture rates of zero) over time (Caughley and Sinclair 1994). If the slope of a regression of animal abundance over time is significantly different from zero, as determined by a t-test, and positive, it indicates a significant increase in abundance over time. If the slope is not significantly different from zero, there is no significant change over time, while if the slope is significantly different from zero and negative then the population has decreased significantly in abundance.

Table 5: West Coast study site – Total captures of individuals during each trapping session T = treatment area, NT = Non-treatment area t

es o o oo on on m m m m m - - d d ur ro mm mm ndic ssu ssu to ssu tal ng ng ushtail ushtail nose Br Br Po Po To Capt nose Ba Lo Po Co Lo Po Co Ringtail

T NT T NT T NT T NT T NT T NT Session 1 Jan-98 0 1 0 0 0 0 0 0 0 0 0 1 Session 2 Apr-98 1 4 0 0 1 0 0 0 0 0 2 4 Session 3 Jul-99 0 2 0 0 0 0 0 0 0 0 0 2 Session 4 Jan-00 1 3 0 0 5 2 0 0 0 0 6 5 Session 5 Jun-00 0 0 0 0 3 3 0 0 0 0 3 3 Session 6 Oct-00 0 0 0 0 1 1 0 0 0 0 1 1 Session 7 Feb-01 0 1 0 0 8 2 0 0 0 0 8 3 Session 8 Jul-01 1 0 0 0 6 3 0 0 0 1 7 4 Session 9 Oct-01 0 0 0 0 3 1 0 0 0 0 3 1 Session 10 Jan-02 2 0 1 0 3 7 0 1 0 0 6 8 Session 11 Apr-02 0 1 1 0 8 6 0 0 0 0 9 7 Session 12 Jun-02 0 1 1 0 8 4 0 1 1 0 10 6 Session 13 Oct-02 1 2 0 0 6 5 0 0 0 1 7 8 Session 14 May-03 2 1 1 0 7 6 0 2 0 0 10 9 Totals 8 16 4 0 59 40 0 4 1 2 72 62

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 28 Table 6: East Coast study site – Total captures of individuals during each trapping session T = treatment area, NT = Non-treatment area Note addition of Southern Brown Bandicoot

t t

rn es oo oo on on m m m m oo oo n n - - d d ur he r mm mm ndic ndic ssu ssu ssu to ut tal ng ng ushtail ushtail ow Po Po Po To Capt Co Br So Po Br Co Ringtail Br Ba Ba Lo nose Lo nose

T NT T NT T NT T NT T NT T NT T NT Session 1 Dec-97 0 0 1 0 0 0 2 0 0 0 0 0 3 0 Session 2 Mar-98 1 0 1 2 2 0 0 1 0 0 1 1 5 4 Session 3 Jun-99 0 0 1 3 0 0 1 0 0 0 0 1 2 4 Session 4 Feb-00 0 0 1 0 0 0 2 0 0 0 2 1 5 1 Session 5 Jul-00 1 0 0 2 1 0 1 0 0 0 1 0 4 2 Session 6 Dec-00 0 0 1 1 5 0 0 0 0 0 0 0 6 1 Session 7 Mar-01 3 1 1 3 2 0 1 0 0 0 3 1 10 5 Session 8 Aug-01 1 0 1 1 3 0 0 0 0 0 2 1 7 2 Session 9 Nov-01 1 0 0 3 5 1 0 0 0 0 0 0 6 4 Session 10 Jan-02 0 0 1 0 7 0 4 0 0 0 3 1 15 1 Session 11 Apr-02 2 1 1 1 9 2 3 0 0 0 2 1 17 5 Session 12 Jul-02 4 2 4 4 11 6 0 1 0 0 1 4 20 17 Session 13 Oct-02 2 0 0 1 16 6 0 0 0 4 0 0 18 11 Session 14 May-03 1 1 2 0 10 8 1 0 0 0 6 4 20 13 Totals 16 5 15 21 71 23 15 2 0 4 21 15 138 70

Table 7: Stony Peak study site – Total captures of individuals during each trapping session T = treatment area, NT = Non-treatment area Note addition of Southern Brown Bandicoot

t t

rn es oo oo on on tain m m m m m oo oo n n - - d d ur he r un mm mm ndic ndic ssu ssu ssu to ut tal ng ng ushtail ushtail ow Co Br Po Po To Capt Mo Po Br Co Ringtail So Br Ba Po Ba nose Lo nose Lo

T NT T NT T NT T NT T NT T NT T NT Session 1 Jan-98 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Session 2 May-98 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Session 3 Aug-99 0 0 4 3 2 0 0 0 0 0 2 1 8 4 Session 4 Mar-00 4 3 4 2 0 0 0 1 0 0 2 0 10 6 Session 5 Aug-00 3 1 2 3 0 0 1 0 0 0 2 0 8 4 Session 6 Oct-00 2 0 2 4 2 0 2 2 0 0 1 1 9 7 Session 7 Apr-01 3 2 5 1 0 0 0 0 0 0 1 3 9 6 Session 8 Sep-01 4 0 1 0 0 0 1 0 0 0 1 0 7 0 Session 9 Nov-01 4 2 2 2 0 0 2 0 1 0 0 0 9 4 Session 10 Feb-02 6 2 2 1 4 1 1 2 2 2 2 0 17 8 Session 11 May-02 2 4 0 0 0 0 0 1 2 1 2 0 6 6 Session 12 Jul-02 2 1 1 1 3 0 0 0 0 1 2 0 8 3 Session 13 Oct-02 2 0 0 1 3 0 0 0 3 2 1 0 9 3 Session 14 Jun-03 5 1 1 0 0 0 0 0 1 0 0 1 7 2 Totals 37 16 24 18 14 1 7 6 9 6 16 6 107 53

29 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Figure 13 Trap success of all CWR species in the West Coast study site expressed as a percentage

0.03

Total - Treatment 0.025

Total - Non-treatment

0.02 cess

0.015

0.01 Percentage Trap Suc

0.005

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Trapping Session

Figure 14: Trap success of all CWR species in the East Coast study site expressed as a percentage

0.05

0.045 Total - Treatment

Total - Non-treatment 0.04

0.035

0.03

0.025 Trap Success ge

0.02 Percenta

0.015

0.01

0.005

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Trapping Session

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 30 Figure 15: Trap success of all CWR species in the Stony Peak study site expressed as a percentage

0.045

Total - Treatment 0.04

Total - Non-treatment

0.035 s

es 0.03 ap Succ ap

Tr 0.025

0.02 Percentage Percentage

0.015

0.01

0.005

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Trapping Session

Figure 16: Total captures per trap night (CPT-1) for Southern Brown Bandicoot Solid line represents captures in treatment areas, broken line represents captures in non-treatment areas

0.016 Southern Brown Bandicoot

0.014 -1 0.012

0.01

0.008 Baiting 0.006 Commenced

Captures trap night 0.004

0.002

Mar-97 Jul-98 Dec-99 Apr-01 Sep-02 Jan-04

Bars on figures 16-21 indicate standard error

31 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Figure 17: Total captures per trap night for Long-nosed Bandicoot Solid line represents captures in treatment areas, broken line represents captures in non-treatment areas

0.012 Baiting Long-nosed Bandicoot Commenced

0.01 -1

0.008

0.006

ptures trap night 0.004 Ca

0.002

Mar-97 Jul-98 Dec-99 Apr-01 Sep-02 Jan-04

Figure 18: Total captures per trap night for Long-nosed Potoroo Solid line represents captures in treatment areas, broken line represents captures in non-treatment areas

0.045 Long-nosed Potoroo 0.04

0.035 -1 t 0.03

0.025

0.02 Baiting Commenced Captures trap nigh 0.015

0.01

0.005

Mar-97 Jul-98 Dec-99 Apr-01 Sep-02 Jan-04

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 32 Figure 19: Total captures per trap night for Common Brushtail Possum Solid line represents captures in treatment areas, broken line represents captures in non-treatment areas

Common Brushtail Possum 0.016

0.014 -1

t 0.012 gh ni

0.01 ap tr 0.008 es

ur 0.006 pt

Ca 0.004

0.002

Mar-97 Jul-98 Dec-99 Apr-01 Sep-02 Jan-04

Figure 20: Total captures per trap night for Common Ringtail Possum Solid line represents captures in treatment areas, broken line represents captures in non-treatment areas2

0.016 Common Ringtail Possum 0.014 -1 0.012 ght 0.01 ap ni ap

tr 0.008 es es

ur 0.006 pt

Ca 0.004

0.002

Mar-97 Jul-98 Dec-99 Apr-01 Sep-02 Jan-04

Figure 21: Total captures per trap night for all mammals Solid line represents captures in treatment areas, broken line represents captures in non-treatment areas

0.05 Total Mammals Combined

-1 0.04 ght

0.03 ap ni ap tr es es

ur 0.02 pt Ca 0.01

Mar-97 Jul-98 Dec-99 Apr-01 Sep-02 Jan-04

33 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Figure 22: Long-nosed Potoroos known-to-be-alive in the East Coast study site

30 December August July 1997 2001 2003

Treatment e Non-treatment

Poison baiting commenced May 1999 Individuals Known-To-Be-Aliv

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Trapping Session

Analysis of results For all the species combined there were significantly more animals caught in treatment areas than non-treatment areas (an average of 0.018 captures per trap night CT-1 in treatment versus 0.010 CT-1 in non-treatment areas), and there was also a significant effect of session (Table 10). The pattern is of an overall increase in individuals captured in both non-treatment and treatment areas but with a greater increase in treatment areas following the initiation of fox baiting, which can be seen in Figure 21. When examining the species separately, there were significant differences in individuals captured between treatments for Long-nosed Potoroo (an average of 0.005 CT-1 in treatment versus 0.003 CT-1 in non-treatment areas) and Southern Brown Bandicoot (an average of 0.012 CT-1 in treatment areas versus 0.003 CT-1 in non-treatment areas). There was a near significant effect for Common Brushtail Possum (P<0.051) [an average of 0.012 CT-1 in treatment areas versus 0.003 CT-1 in non-treatment areas (Table 8e)]. There was no significant effect of treatment for Common Ringtail Possum and Long-nosed Bandicoot; indeed the significant effect of session shows that Long-nosed Bandicoot declined in both treatment and non-treatment areas over the course of the study (Figure 17 ).

For all species there were significant effects of block indicating major differences in species abundance between blocks. The major differences in abundance between blocks also accounted for the high standard errors for mean treatment capture rates.

On average, the maximum interval between captures was higher in treatment areas for Common Brushtail Possums, Mountain Brushtail Possums and Long-nosed Potoroos and higher in non-treatment areas for both species of bandicoots. Four species had sufficient recapture data to analyse differences in survivorship. There was no significant difference in maximum time between recaptures for Common Brushtail Possum (t = 1.31, P = 0.10), Long-nosed Bandicoot (t = 1.94, P = 0.32), or Southern Brown Bandicoot (t = 1.89, P = 0.40) but there was a significant difference for Long-nosed Potoroo (t = 1.7, P = 0.03).

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 34 For the site-specific analysis of rates of increase there was a significant change for three species in three separate study sites. These significant results were for Long-nosed Potoroo in both treatment (r = 0.77, F = 66.34, P = 0.00001) and non-treatment areas (r = 0.64, F = 18.88, P = 0.0014) in the East Coast study site. There was also a significant increase in abundance in Common Brushtail Possum in treatment (r = 0.37, F = 6.87, P = 0.026) and non-treatment areas (r = 0.40, F = 14.28, P = 0.0036) in the West Coast study site. There was a significant decrease in Long-nosed Bandicoot in treatment (r = -0.36, F = 11.53, P = 0.0068) and non-treatment areas (r = -0.37, F = 11.06, P = 0.0077) in the Stony Peak study site.

Table 8: General Linear Mixed Model for Mammal Species

8a (All Species Combined)

Source Numerator df Denominator df F Significance

Block 2 54.000 2.921 .062

treatment 1 54.000 17.362 .000

treatment * Session 13 54.000 .734 .722

Session 13 54.000 3.546 .001

Covariance Structure: First Order Factor Analytic

8b (Southern Brown Bandicoot)

Source Numerator df Denominator df F Significance

Block 1 27.000 10.353 .003

treatment 1 27.000 10.353 .003

treatment * Session 13 27.000 .400 .957

Session 13 27.000 1.189 .338

Covariance Structure: First Order Factor Analytic

8c (Long-nosed Bandicoot)

Source Numerator df Denominator df F Significance

Block 2 3.171 11.926 .033

treatment 1 4.977 0.540 .496

treatment * Session 13 7.036 2.928 .079

Session 13 7.036 3.917 .039

Covariance Structure: First Order Ante-Dependence

35 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 8d (Long-nosed Potoroo)

Source Numerator df Denominator df F Significance

Block 1 27.000 11.798 .002

treatment 1 27.000 10.745 .003

treatment * Session 13 27.000 .542 .877

Session 13 27.000 1.744 .108

Covariance Structure: First Order Factor Analytic (Constant Diagonal Offset)

8e (Common Brushtail Possum)

Source Numerator df Denominator df F Significance

Block 2 190.234 52.147 .000

treatment 1 37.997 4.075 .051

treatment * Session 13 7.678 .339 .959

Session 13 7.678 1.282 .376

Covariance Structure: First Order Factor Analytic (Heterogeneous Diagonal Offset)

8f (Common Ringtail Possum)

Source Numerator df Denominator df F Significance

Block 2 54.000 8.346 .001

treatment 1 54.000 3.803 .056

treatment * Session 13 54.000 1.000 .465

Session 13 54.000 .750 .707

Covariance Structure: First Order Factor Analytic (Constant Diagonal Offset)

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 36 Rainfall data Table 9 tabulates the anomaly in the rainfall from the average rainfall figures in far East Gippsland for consecutive 36-month periods. The data covers periods from the start of February 1999 (when poison baiting commenced) until the end of June 2003 (when the last trapping session took place). An example of the rainfall anomaly over a 36-month period is given in Figure 23, which illustrates the rainfall anomaly between April 1999 and March 2002. Clearly, the area in which the research was undertaken experienced a rainfall deficit of between 250 and 500 mm.

While there were individual months throughout the study when rainfall exceeded the monthly average, there was never a prolonged period during the study (once poisoning of foxes started) that the rainfall in East Gippsland was not in overall deficit (Table 9). As rainfall is fairly evenly distributed throughout the year in East Gippsland, it can be seen that for half of the periods, rainfall was between approximately 25% and 60% below average.

Figure 23: Rainfall anomalies for Victoria from the 1st of April 1999 until the 31st of March 2002

Rainfall anomaly (mm)

5000mm

2500mm

1500mm

1000mm

500mm

250mm

0mm

-250mm

-500mm

-1000mm

-1500mm

-2500mm

-5000mm

www.bom.gov.au

(Source: Bureau of Meteorology website)

37 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Table 9: Rainfall anomaly figures for Far East Gippsland for consecutive 36-month periods Note that every period is in rainfall deficit of between 0 and 500mm (i.e. none of the periods experienced rainfall in excess of the average).

36-month time period Rainfall anomaly for far East Gippsland (rainfall deficit) (mm)

February 1999 – January 2002 250 – 500

March 1999 – February 2002 0 – 250

April 1999 – March 2002 250 – 500

May 1999 – April 2002 0 – 500

June 1999 – May 2002 0 – 500

July 1999 – June 2002 0 – 250

August 1999 – July 2002 0 – 250

September 1999 – August 2002 0 – 250

October 1999 – September 2002 0 – 250

November 1999 – October 2002 0 – 250

December 1999 – November 2002 0 – 250

January 2000 - December 2002 250 – 500

February 2000 – January 2003 250 – 500

March 2000 – February 2003 250 – 500

April 2000 – March 2003 250 – 500

May 2000 – April 2003 250 – 500

June 2000 – May 2003 250 – 500

July 2000 – June 2003 250 – 500

Source: Bureau of Meteorology

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 38 Section 6

Discussion and Conclusions

Comparison to other studies

A range of other studies have demonstrated population responses by Australian mammals to fox control (Kinnear et al. 1988; Friend, J.A. 1990; Kinnear et al. 1998; Banks et al. 2000), although not all species have responded positively (Banks 1998). Studies in the native range of the Red Fox in the Northern Hemisphere have also shown that fox predation can have a profound effect on the abundance of co-adapted prey species (Lindstrom et al. 1994). The current study demonstrates the diversity of responses by a range of mammal species to reduced fox abundance with an overall greater abundance of mammals in treatment areas but no consistent inter-specific patterns in response to fox baiting.

In other mammalian predator-prey systems, long-term changes in prey abundance are an interaction between the top-down forces of predation and the bottom-up forces of stochastically varying food supply (Meserve et al. 2003). Despite the below-average rainfall experienced across the study sites for over 40 months of the study, overall mammal captures increased, indicating that resources were still sufficiently abundant for most mammals to increase in population size in response to decreased predation.

Responders – Long-nosed Potoroo & Southern Brown Bandicoot Two species in particular, Long-nosed Potoroo and Southern Brown Bandicoot, had significantly higher abundance in treatment areas following fox control. Notably, Long-nosed Potoroo and Southern Brown Bandicoot are the species that have suffered the greatest decline in distribution and abundance since the arrival of the fox in East Gippsland. There were relatively high capture rates of Long- nosed Potoroos in the treatment areas, particularly in the East Coast study site (see Figure 22), where significant positive rates of increase were observed. It is possible that these high rates of capture were facilitated by the potoroo being a relatively social animal with many individuals sharing home ranges (Long 2001) compared with the Southern Brown Bandicoot, which shows a degree of

39 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria territoriality and intra-specific aggression (Thomas 1990). Presumably, the Long-nosed Potoroo is more tolerant of higher population densities than either bandicoot species, despite similar body sizes and energetic requirements. Mean maximum capture interval was significantly greater for potoroos in the treatment areas, so it seems that reduced predation pressure may have increased adult survival.

Meserve et al. (2003) suggested that a long lifespan and sociability might contribute to the persistence of some Chilean rodent species in the face of environmental stress. Perhaps the social nature and natural longevity of potoroos may contribute to their ability to persist in small isolated pockets of suitable habitat of East Gippsland forest in the presence of foxes, as has been observed.

During the course of this study, the long period of below average rainfall would appear to have not disadvantaged the Long-nosed Potoroo. This is a species that exhibits a K-selected reproductive strategy (few offspring that tend to be large and receive intensive parental care), and which consumes a food resource that is relatively more secure in the face of environmental perturbations. Claridge et al. (1993), in a study of sporocarp production in East Gippsland, found that while the number of sporocarps produced varied, and that production varied across the catchment, overall production by weight did not alter significantly over time. Potoroos may have been able to benefit from this relatively reliable food source during prolonged periods of below-average rainfall.

Mixed response – Long-nosed Bandicoots The lack of response from Long-nosed Bandicoots in the West Coast and East Coast study sites and the decline in the Stony Peak study site is curious given that other members of the genus Perameles have been shown to respond well to fox control (Short et al. 1998). There are several possible reasons why this species may not have shown the anticipated positive response. One is that in eastern Victoria the Long-nosed Bandicoot is at the southern edge of its range, and hence abundance may be inherently low irrespective of predation pressure (Caughly et al. 1988). Alternatively, competitive interactions with the more dietary specialised Southern Brown Bandicoot and Long-nosed Potoroo, or even Dusky Antechinus (Antechinus swainsonii), may have inhibited its population response.

The most likely explanation, however, is that the abundance of Long-nosed Bandicoots may be more strongly tied to the prevailing environmental conditions. Population dynamics of other species of Perameles in both arid and humid environments have been shown to be sensitive to variations in rainfall (Short et al. 1998; Mallick et al. 2000). Mallick et al. (1998) monitored two populations of I. obesulus in Tasmania, and attributed the decline they observed in the population to the unusually dry conditions experienced during the course of their study. Dry conditions result in a reduced abundance of leaf litter and soil dwelling invertebrates, a key food resource for bandicoots (Lobert and Lee 1990). Lobert and Lee (1990) suggested that female I. obesulus are capable of altering their reproductive output in response to changes in rainfall and subsequent food availability, noting both a decline in litter size and number of litters when food abundance is low. Similar trends in breeding related to rainfall patterns and ultimately food supply were observed in the Northern Brown Bandicoot (Isoodon macrourus) in Kakadu National Park (Friend, G.R. 1990).

Claridge et al. (1991) and Claridge (1993) found that Perameles nasuta consumed considerably less hypogeal fungal material than either I. obesulus or Potorous tridactylus respectively. Claridge and Cork (1994) noted that bandicoots have relatively simple alimentary systems compared to those possessed by potoroos, with no marked enlargement of the forestomach. Lacking the capacity to delay and ferment foods in the forestomach, bandicoots probably derive little energy from digestion of the complex carbohydrates of the fungal cell walls that make up hypogeal sporocarps (Claridge and Cork 1994). Claridge and Cork (1994) postulated that bandicoots were physiologically constrained to eating digestible foods to support reproduction, and utilise fungus only as a supplementary food. It may be that the population responses observed in this study amongst the three species of truly terrestrial CWR mammals are related to a ‘dietary continuum’ along which the three species exist. Long-nosed Potoroos appear to be the most mycophagous, Long-nosed Bandicoots appear to be the most insectivorous, and Southern Brown Bandicoots lie somewhere in between. As can be seen in the rainfall data provided above, East Gippsland experienced a prolonged period of below-average rainfall during the time that this study was undertaken. The implication of this is that overall productivity is reduced, which has a flow-on effect on invertebrate numbers and those species that consume invertebrates, such as bandicoot species.

It is difficult to account for the decline in captures in the Stony Peak study site subsequent to trapping session ten. Possibly being slightly more inland, and in an area consisting of granitic soils that drain particularly quickly, the effects of a prolonged drier period may be more keenly felt. Alternatively, foxes may have reinvaded the site and been responsible for the decline. Given the density of the understorey in the site this does not seem to be a likely explanation.

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 40 Mixed response – Common Brushtail Possum Overall, Common Brushtail Possum did not show a significant response to fox baiting. However, the West Coast study site was an exception with the observed rate of increase being significant and positive for Common Brushtail Possum. While the estimated r was below the theoretically derived estimate of rm, it was well above an empirically derived estimate of rm = 0.22 for a population recovering from a control operation in a New Zealand forest, where the species is introduced and regarded as a pest (Hickling & Pekelharing 1989).

Insignificant response - Common Ringtail Possum The Common Ringtail Possum did not show a significant response to fox baiting. Given that Common Ringtail Possums are the most arboreal of the mammal species examined it is possible that their population dynamics are more influenced by climbing and flying native predators like lace monitors and owls (Lavazanian et al. 1994; Russell et al. 2003), or by food availability than fox predation.

Overall variability and habitat The significant differences in capture rates and abundance between study sites for all species tested suggest a very heterogeneous mammal community throughout East Gippsland. Part of this heterogeneity may be due to the interaction between fox predation and refuge from predation provided by dense vegetation. Habitat structure has been shown to have a profound effect on predation rates with dense vegetation providing refuge by hindering access by predators (Arthur et al. 2004). The chief habitat difference between the East Coast and West Coast study sites was the presence of extremely dense heath in the East Coast study site. It is likely that populations of Long-nosed Potoroo and Southern Brown Bandicoot persisted in the East Coast study site because of the presence of this heath vegetation, a preferred habitat in studies where foxes have not been controlled (Stoddart and Braithwaite 1979; Bennett 1993). Long-nosed Potoroos were captured in low numbers in the West Coast treatment area, although these captures were made primarily in dense riparian vegetation.

Site variability When the response of individual populations in individual sites was examined, Long-nosed Potoroo and Common Brushtail Possum increased significantly, but Long-nosed Bandicoot declined significantly. In each of these cases the rate of increase was of a similar direction and magnitude, but for the two species that increased, overall abundance was higher in treatment areas. The similar responses in non-treatment and treatment areas for Common Brushtail Possum in the West Coast study site, Long-nosed Potoroo in the East Coast study site, and Long-nosed Bandicoot in the Stony Peak study site suggests that other unmeasured environmental factors may be driving population change. For both the Common Brushtail Possum and Long-nosed Potoroo, the measured rates of increase were below the predicted rm for these species (0.667 for Common Brushtail Possum and 1.058 for Long-nosed Potoroo respectively, Thompson 1987). However, it is difficult to imagine what variable could cause the sustained increase in abundance of potoroos and brushtail possums and at the same time could cause a decrease in the abundance of Long-nosed Bandicoots. Indeed, an examination of the figures shows that for almost all species, population abundance was very low prior to baiting and increased in both treatment and non-treatment areas following baiting, generally to a higher level in treatment areas.

A possible explanation for the increase in non-treatment areas as well as treatment areas is the immigration of mammals from the treatment to non-treatment areas. Alternatively, after several years of ongoing baiting, the treatment areas may have acted as relatively large ‘sinks’ for foxes, resulting in a reduced fox population in an area considerably larger than that within which baits were placed. The continual removal of foxes brought about by the poisoning program could result in the same phenomenon of home range drift amongst foxes outside of the area in which baits are laid, similar to that witnessed in a population of foxes by Doncaster and Macdonald (1991). The populations of mammals inhabiting the non-treatment areas may therefore have also experienced a reduction in predation pressure, brought about by the reduced fox population.

There is no direct evidence for either phenomenon, as no mammals were ever recorded moving from one site to another and no fox scats with coloured marker beads were found within a site that were likely to have emanated from the corresponding treatment or non-treatment area. Despite this, it is possible that either phenomenon—perhaps in combination—may be responsible for the observed patterns. If dispersal of mammals from treatment to non-treatment areas occurs shortly after juveniles leave the pouch then immigration would not have been detected since pouch young were not marked in this study. Alternatively, the continual removal of foxes from baited treatment areas is likely to draw foxes into the vacant territories within these sites where they are in turn poisoned.

41 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria The part of the study in which fox scats were examined for marker beads took place before the poisoning program commenced. Hence it took place before there was a disruption to the social stability of the fox population caused by baiting, and the treatments in each pair of sites appeared independent.

In eastern Australian forests, foxes are known to rapidly occupy vacant home ranges once the original occupant has died (Meek and Saunders 2000). These foxes are frequently part of a transient population of juveniles that can disperse substantial distances or are subordinate foxes with home ranges of inadequate quality. Creating an area with a high density of prey and no intra-specific competitors may drain the area of these foxes well beyond the periphery of the baited area. If any of these processes are operating then the independence of the samples is qualified but it does suggest that the dynamics of foxes and their prey are operating on a very broad landscape scale.

Conclusions An observed increase in abundance of Long-nosed Potoroo and Southern Brown Bandicoot was very encouraging and provided evidence that the fox baiting strategy could deliver successful ecological management outcomes for Victoria’s small native animals.

Data for Common Brushtail Possum did not indicate an appreciable change in the abundance. For this long-lived species, evidence of a response may require a longer observation timeframe. Data for Long-nosed Bandicoot indicated an appreciable decline in abundance. It is plausible that the decline in this species may have been caused by a prolonged period of below-average rainfall that coincided with the course of the project.

The authors regard the implementation of ongoing fox control across large areas of forest as a major opportunity to improve the conservation outcomes of forest-dwelling mammalian fauna, and potentially other species preyed on by foxes, in south-eastern Australia.

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 42 Appendix 1:

Habitat Complexity as a Determinant of Mammal Populations

Catling and Burt (1995) found that in areas where foxes are regarded as abundant, there appears to be a positive relationship between the level of habitat complexity and the density of populations of ground- dwelling mammals. That is, greater numbers of ground-dwelling mammals appear to inhabit areas with dense (‘complex’) habitat, especially in the understorey component. However, even in areas of relatively complex habitat such as the mesic forests in far East Gippsland, populations of CWR mammals appear to have declined, except perhaps in the densest of habitats. It was therefore important in this study to demonstrate that in the absence of foxes, sufficient habitat was available for populations of CWR mammals to increase in their distribution as well as their abundance. It was also important to demonstrate that each pair of sites was not only similar in terms of past land management and vegetation type, but that the levels of habitat complexity were also comparable.

Within each treatment area and each non-treatment area a transect of 60 cage-traps was established along an 18km transect (traps placed at 300m intervals), in order to monitor the population response of CWR mammals to fox control. The habitat complexity of each trap site was scored, based on a visual method of scoring complexity developed by Newsome and Catling (1979). This method scores the complexity (from 0 to 3) of five components of the habitat: (1) the percentage of canopy cover; (2) shrub cover; (3) ground cover; (4) the amount of leaf litter, fallen logs and rocks; and (5) a soil moisture rating. When rating each trap site, it was imagined that the trap was in the centre of a 50m2 patch of forest. Table 12 provides details concerning the scores available for each of these components.

43 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Table 10: Visual method for scoring complexity of the habitat at trap sites (Newsome and Catling 1979)

Complexity Rating

Habitat Component 0 1 2 3

Tree Canopy (%) 0 <30 30-70 >70

Shrub Canopy (%) 0 <30 30-70 >70

Ground herbage Sparse, <0.5m Sparse, >0.5m Dense, <0.5m Dense, >0.5m

Logs, rocks, woody debris, etc. 0 <30 30-70 >70 (ground cover %)

Moisture in the soil Dry Moist Permanent water adjacent Water-logged

The overall habitat complexity is determined by tallying the scores for each component. Those sites with an open canopy, light shrub and understorey layers, not much woody debris and low soil moisture are usually given a Habitat Complexity Score of 4 or 5, which is considered to be a ‘low’ score. At the other end of the scale, those sites with a well-developed canopy, dense shrub and understorey layers, large amounts of woody debris and leaf litter, and high soil moisture content, tend to be given a score of 9 or more. These sites are regarded as having a ‘high’ Habitat Complexity Score. Sites that recorded a score of 6, 7 or 8 were regarded as having a ‘moderate’ Habitat Complexity Score.

Figures 24-26 illustrate the Habitat Complexity Scores for each of the three study sites. It can be seen that each ‘treatment area’ and each associated ‘non-treatment area’ are comparable to each other. Both the East Coast and Stony Peak study sites have a high percentage of sites with high habitat complexity and only a very few sites with low habitat complexity. The majority of sites in the West Coast study site had moderate habitat complexity, with few sites having either low or high complexity. It is therefore concluded that within each pair of sites the level of habitat complexity is broadly similar. It can also be concluded that given the level of habitat complexity across all study sites, the opportunity is present for CWR species to increase in abundance and distribution following the decline in the fox population as poison baiting is implemented.

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 44 Figure 24: Habitat Complexity Scores for trap sites located in the West Coast study site

45 Treatment 40 Non-treatment

30 s te Si 25 ap Tr

er 20 mb Nu 15

0 Low Medium High

Habitat Rating

Figure 25: Habitat Complexity Scores for trap sites located in the East Coast study site

35 Treatment Non-treatment

30 s te Si

ap 25 Tr

er 20 mb

Nu 15

0 Low Medium High Habitat Rating

45 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria Figure 26: Habitat Complexity Scores for trap sites located in the Stony Peak study site

Treatment 35 Non-treatment

30 s

te 25 Si

ap tr 20 of

mb 15 Nu

0 Low Medium High

Habitat Rating

Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria 46 References

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49 Project Deliverance: the response of ‘critical-weight-range’ mammals to effective fox control in mesic forest habitats in far East Gippsland, Victoria www.dse.vic.gov.au