Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

P. W. Menkhorst and P. V. Macak

January 2013

Arthur Rylah Institute for Environmental Research Unpublished Internal Report for Fire Branch, Department of Sustainability and Environment

Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

Peter Menkhorst and Phoebe Macak

Arthur Rylah Institute for Environmental Research 123 Brown Street, Heidelberg, Victoria 3084

January 2013

Arthur Rylah Institute for Environmental Research Department of Sustainability and Environment Heidelberg, Victoria

Report produced by: Arthur Rylah Institute for Environmental Research Department of Sustainability and Environment PO Box 137 Heidelberg, Victoria 3084 Phone (03) 9450 8600 Website: www.dse.vic.gov.au/ari

© State of Victoria, Department of Sustainability and Environment 2013 This publication is copyright. Apart from fair dealing for the purposes of private study, research, criticism or review as permitted under the Copyright Act 1968, no part may be reproduced, copied, transmitted in any form or by any means (electronic, mechanical or graphic) without the prior written permission of the State of Victoria, Department of Sustainability and Environment. All requests and enquiries should be directed to the Customer Service Centre, 136 186 or email [email protected]

Citation: Menkhorst, P.W. and Macak, P,V. (2013) Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria. Arthur Rylah Institute for Environmental Research Unpublished Internal Report for Fire Branch, Department of Sustainability and Environment, Heidelberg, Victoria

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 purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.

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Front cover photo: The strategic fuelbreak on the northern ridge of Mt Terrible, October 2010 (Peter Menkhorst). Printed by: NMIT Printroom, 77 St Georges Rd, Preston 3072

Contents List of tables and figures ...... vi Acknowledgements ...... vii Summary ...... 1 1 Introduction ...... 2 1.1 The Issue ...... 2 1.2 The Smoky Mouse ...... 2 1.3 Project Aims ...... 3 2 Methods ...... 4 2.1 Locating a study population ...... 4 2.2 Study area description ...... 5 2.3 Capture and Marking ...... 7 2.4 Radio-tracking ...... 8 3 Results ...... 11 3.1 Trapping ...... 11 3.2 Radio-tracking ...... 13 4 Discussion ...... 16 4.1 Movements revealed by trapping and radio-tracking...... 16 4.2 Likely impacts of the fuelbreak on population processes ...... 16 4.3 Trapping rates ...... 17 4.4 Other natural history information gleaned from the study ...... 17 References ...... 18

List of tables and figures List of tables Table 1. Field trips conducted during the investigation of the impacts of strategic fuelbreaks on the Smoky Mouse at Mt Terrible...... 9 Table 2. Details of each Smoky Mouse captured and marked at Mt Terrible, 2010-2011 ...... 12 Table 3. Numbers of detected fuelbreak crossings by radio-collared Smoky Mice...... 14 Table 4. Locations of radio-tagged Smoky Mice during night-time tracking sessions in relation to the daytime nest site used the day before ...... 14

List of figures Figure 1. Smoky Mouse Pseudomys fumeus trapped at Mt Terrible, May 2010 ...... 3 Figure 2. Study location ...... 4 Figure 3. Map of study area showing all trapping grids used, and Smoky Mouse nesting sites ...... 5 Figure 4. Strategic fuelbreak passing through Eucalyptus rubida Montane Dry Woodland at the Mt Terrible study site, May 2010, two years after construction of the fuelbreak ...... 6 Figure 5. Typical Eucalyptus dives Montane Dry Woodland in the north-western part of the study area, with the Mt Terrible Track visible on the right ...... 6 Figure 6. Smoky Mouse 0-1 showing indentifying ear tattoos ...... 7 Figure 7. Radio collar package used in this study ...... 10 Figure 8. Smoky Mouse with radio-collar attached ...... 10 Figure 9. Radio-tracking to locate daytime nesting sites...... 11 Figure 10. Entrance to Smoky Mouse nest hole, Mt Terrible, October 2011 ...... 15

vi

Acknowledgements This project was commissioned and funded by the Land and Fire Management Branch of DSE. It was overseen by a Project Control Group comprising Aaron van Winden (Chair), Al Beaver, Gordon Friend, Richard Loyn, Stephen Platt, Mario Malovic (Melbourne Water) and John Wright (Parks Victoria). Colleagues Ryan Chick and Jenny Nelson assisted in the identification of Mt Terrible as a suitable study site. Technical assistance in the field and workshop was kindly provided by Ryan Chick, who was instrumental in giving radio-tracking instruction and assistance, and Mike Lindeman (ARI), Rena Gaborov (Wildlife Unlimited), Fiona Freestone and Joe Henderson (volunteers). Nigel Brennan (DSE Woori Yallock) assisted with our understanding of the strategic fuelbreaks project and Emily Borton (DSE Alexandra) provided advice on track conditions. Maps were produced using the DSE Biodiversity Interactive Mapping system. Richard Loyn, Dan Harley, Rodney van der Ree, Lee Harrison and Joanne Ainley provided helpful input into project design and methods. Field work was carried out under Wildlife Research Permit number 10005394 and approval number 10/04 from the Arthur Rylah Institute Animal Ethics Committee. Helpful comments on a draft of this report were provided by Stephen Platt, Richard Loyn, Jenny Nelson and Alan Robley.

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viii Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

Summary Following a series of large bushfires in central Victoria, the Victorian Government initiated the construction of strategic fuelbreaks around Melbourne’s water catchments in 2007. Approval for construction under the Environment Protection and Biodiversity Conservation Act (1999) (EPBC Act) was obtained with the proviso that the completed fuelbreaks be subject to formal assessment of potential impacts on threatened fauna. The Smoky Mouse was selected as one of the species to be investigated, as fuelbreaks were likely to pass through its habitat and it is listed as endangered under the EPBC Act. The Smoky Mouse is a small native rodent that has a fragmented distribution, with evidence of declines and disappearance from some areas (Menkhorst and Broome 2008). The main concern was that strategic fuelbreaks may act as a barrier to movement for the species if it was reluctant to cross the cleared break. This could lead to populations effectively being split into smaller units. A population of Smoky Mice, located on both sides of a strategic fuelbreak at Mt Terrible, in the upper Goulburn River catchement, was studied from May 2010-December 2011 to determine whether animals were crossing the break. Trap-mark-recapture techniques and radio-telemetry were employed to determine the movements of individual animals. The fuelbreak had been constructed 17 months before this study began. Of 33 individual Smoky Mice marked during the study, seven were recorded as having crossed the fuelbreak. Three males were trapped on both sides of the fuelbreak (4.4% of a total of 68 captures), indicating that they had crossed between captures. Radio-tracking of five radio-collared animals revealed that they frequently crossed the fuelbreak, some on every night they were tracked, and some on multiple occasions through a single night. One animal was also discovered to have made several crossings over a nearby vehicle track, which was in existence long before the fuelbreak. Animals of both sexes were shown by radio-tracking to cross the break. Radio-tracking also enabled the location of nest burrows in which the Smoky Mice sheltered during daylight to be determined. These burrows were shared by multiple adults of both sexes, supporting previous studies that suggest that the Smoky Mouse is a communal, plural breeder. Our results indicate that on Mt Terrible there is no detectable barrier effect on Smoky Mouse movements due to the fuelbreak. We surmise that the result at this location can be applied along the strategic fuelbreak network. Accordingly, it seems unlikely that fuelbreaks are acting as a barrier that could lead to a change in population status resulting from reduced gene flow or dispersal. However, we did not investigate changes to predation rates that may result from construction of the fuelbreaks, for example, by allowing ingress of introduced predators and forcing Smoky Mice to venture onto cleared areas.

1 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

1 Introduction 1.1 The Issue In January 2007, in the wake of serious bushfires in preceding years, the Victorian Government announced a program to construct strategic fuelbreaks in and around Melbourne’s water catchment areas and other critical infrastructure. Construction of the fuelbreaks involved the permanent removal of understorey, logs and some, but not all, trees from linear transects 20-40 m wide and totalling several hundred kilometres in length. The Commonwealth Minister for Environment determined that construction of fuelbreaks warranted formal assessment under the Environment Protection and Biodiversity Conservation Act (1999) because fuelbreaks were likely to pass through habitat of nationally-listed threatened flora and fauna. Conditions placed on the EPBC Act approval for the fuelbreaks project required investigations of the potential impacts on two nationally-threatened mammal species thought most likely to be adversely affected – the Smoky Mouse Pseudomys fumeus and Leadbeater’s Possum Gymnobelideus leadbeateri. This project investigated potential impacts on the Smoky Mouse. The primary concern was that populations of the Smoky Mouse could be effectively split into smaller units if the fuelbreak formed a barrier to movement for that species. Such smaller populations separated by a barrier may be more susceptible to chance events and loss of genetic diversity than the original larger and more expansive population would have been.

1.2 The Smoky Mouse The Smoky Mouse is a small native rodent about 2–3 times the size of the introduced House Mouse Mus musculus (Figure 1). Total length ranges from 180 mm to 250 mm, with the tail accounting for more than half of this. The ears are 18–22 mm long and the hind feet 25–29 mm long. Adult weight varies widely, from 35 g to 86 g (but in this study ranged from 40–60 g). The fur is pale smoky grey above and whitish below. The tail is long, thin, flexible, and covered with short, fine hairs which are white to pale pinkish grey underneath and brown-grey in a narrow stripe along the upper surface. The ears and feet are pinkish, with sparse white hair (Menkhorst and Knight 2011). The Smoky Mouse is endemic to mainland south-eastern Australia where it occurs in Victoria, south-eastern New South Wales and the Australian Capital Territory. Capture sites range from near sea level to at least 1800 m altitude (Menkhorst and Broome 2008b). The Smoky Mouse is an enigmatic species about which little is known (Menkhorst and Seebeck 1981, Ford et al. 2003, Menkhorst and Broome 2008a). There are no data on which to base population estimates or to estimate population trends, but some studied populations have clearly declined. Prior to 1985, the species was considered to be endemic to Victoria (Menkhorst and Seebeck 1981) but, since then, records from south-eastern NSW and the ACT have substantially expanded the known range. Within this range, populations are fragmented and generally low in number, but can fluctuate in size. There is also evidence of apparent local extinctions (Menkhorst and Broome 2008a).

2 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

Figure 1. Smoky Mouse Pseudomys fumeus trapped at Mt Terrible, May 2010 (P. Menkhorst).

The Smoky Mouse occurs in a variety of vegetation communities, ranging from coastal heath to dry ridgeline forest, sub-alpine heath and, occasionally, wetter gullies (Menkhorst and Seebeck 1981). Except for the wetter sites, a consistent feature of the vegetation at Smoky Mouse capture sites is the diversity of low, heathy shrubs, combined with potential shelter sites in the form of woody debris or rocks (Menkhorst and Seebeck 1981, Ford et al. 2003). The vegetation at capture sites varies widely in age post-fire (Menkhorst and Broome 2008b, Macak and Menkhorst unpublished data). A study of a small captive colony housed at Melbourne Zoo indicated that the Smoky Mouse is entirely nocturnal and that its activity levels vary little throughout the night (Woods and Ford 2000). Little is known about whether individual Smoky Mice would be willing to cross a large area cleared of vegetation as presented by a fuelbreak. Ford et al. (2003) used radio- telemetry to investigate habitat preferences and nest locations in Nullica State Forest, in south- east NSW, but provided no data on movement patterns or home ranges.

1.3 Project Aims This project originally had two broad aims: 1. To investigate the degree to which the strategic fuelbreak at Mt Terrible acts as a barrier to movement of the Smoky Mouse. 2. To investigate habitat manipulations that would alleviate any barrier effects detected.

During the course of the study we were also able to investigate other aspects of Smoky Mouse natural history including daytime nest locations and usage patterns.

3 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

2 Methods 2.1 Locating a study population Data on Smoky Mouse locality records from the general area targeted for the Strategic Fuelbreaks Programme were extracted from the Victorian Biodiversity Atlas database. These records indicated that fauna surveys conducted in the 1980s located the Smoky Mouse at several sites in the upper catchments of the Yarra and Goulburn Rivers (Lumsden et al. 1991, Menkhorst 1996). During 2009, whilst trialling survey techniques for cryptic small mammals, Nelson et al. (2010) established that a population of Smoky Mice persisted at a site originally located during the 1980s surveys. Fortuitously, this site was adjacent to a newly-constructed fuelbreak on the northern ridge of Mt Terrible, 135 km east-north-east of Melbourne (Figure 2).

Figure 2. Study location

This site was further investigated during May 2010 when exploratory trapping suggested that it would be feasible to capture multiple animals there on both sides of the fuelbreak. To gain further understanding of the extent of the Smoky Mouse population along this fuelbreak, we deployed heat-in-motion triggered survey cameras during June 2010. Smoky Mice were detected by 9 of 11 cameras set in a range of forest types on both sides of the fuelbreak. Based on these results, this ~ 800 m stretch of fuelbreak, which had been constructed between February and May 2008, was selected as a suitable study site.

4 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

2.2 Study area description The study site was centred on a section of the northern ridge of Mt Terrible (37°23’S, 146°7’ E) (Figure 3), and varied in altitude from 1192 m to 938 m. Vegetation varied from Sub-alpine Woodland of Eucalyptus pauciflora and E. dalrympleana at the highest elevations on the southern boundary (see cover photo) to Montane Dry Woodland of E. rubida in the central section (Figure 4) and Montane Dry Woodland of E. dives and E. rubida/E. dalrympleana on the western fall at lower altitudes (Figure 5). Smoky Mice were detected in each of these vegetation communities. Within the general area the strategic fuelbreak mostly follows the existing Mt Terrible Track, however, at the northern end of our study site the track diverges to the west of the ridge to avoid a steep ridge section while the fuelbreak continued straight along the ridge. The fuelbreak meets the track further along, at the southern end of the study site (Figure 3).

Figure 3. Map of study area showing all trapping grids used, and Smoky Mouse nesting sites. Red grids show areas trapped during radio-tracking component.

5 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

Figure 4. Strategic fuelbreak passing through Eucalyptus rubida Montane Dry Woodland at the Mt Terrible study site, May 2010, two years after construction of the fuelbreak (P. Menkhorst).

Figure 5. Typical Eucalyptus dives Montane Dry Woodland in the north-western part of the study area, with the Mt Terrible Track visible on the right (P. Menkhorst).

6 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

2.3 Capture and Marking To establish that an animal has moved from point A to point B requires the ability to recognise individual animals. Therefore, it was necessary to capture Smoky Mice and give each a unique and permanently recognisable mark. We tattooed a numeral into both the left and right ear pinna of each captured Smoky Mouse to form a unique combination (Figure 6). Tattoos were applied with tattooing pliers (Hauptner) using 5 mm digits, and black tattooing ink.

Figure 6. Smoky Mouse 0-1 showing indentifying ear tattoos – 0 in the left ear and 1 in the right (P. Menkhorst). Beginning in May 2010 (Table 1), Smoky Mice were captured and marked on a total of eight trapping grids (Figure 3), with their locations based on those survey cameras which had returned Smoky Mice records. Grids were made up of variable numbers of parallel trap lines approximately 10 or 20 m apart, depending on the particular grid. Grids were placed in the landscape such that they included the fuelbreak verge and extended into the forest away from the break. Trapping lines ran either parallel or perpendicular to the fuelbreak. The furthest a trap line extended from the fuelbreak into the forest was about 80 m. Seven of the grids were approximately square in shape, made up of five lines of ten traps or four lines of fifteen traps. One grid between the fuelbreak and Mt Terrible Track consisted of three lines that extended along its length for a total of 120 m. Trap lines comprised aluminium box traps (330 x 100 x 90 mm, Elliott Scientific) placed on the ground 10-15 m apart. Each trap was baited with a mixture of rolled oats, golden syrup and peanut butter. Cotton wadding and a small rubber mat were placed in traps to provide protection for trapped animals. Plastic bags with drainage holes were used to shield traps from rain. Each trapping session involved 2-3 of the grids such that trapping occurred in areas on both sides of the fuelbreak that were opposite each other. Not all of the trapping grids were successful in capturing animals and most of the trapping effort was concentrated on three that returned the most individuals. These were at the northern end of the study side and comprised the long, narrow grid between Mt Terrible Track and the fuelbreak, and two on the other side of the fuelbreak. It was

7 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

from these grids that animals were selected for radio-tracking (Figure 3). Trapping sessions had multiple purposes – locating the extent of the population along that section of fuelbreak, establishing where animals were most likely to be captured, recapturing individuals to compare which side they were on, and capturing animals for radio-tracking purposes (Table 1). Thus the number of traps deployed during each session varied and trap lines were sometimes extended or shortened according to the purpose. Later in the project, traps were also set around known nesting burrows in order to re-trap particular individuals that had been radio-tagged. Trapping during the preliminary capture and marking phase of the study extended over three or four nights per field trip and totalled 1808 trap nights over four field trips (trips 4-7 in Table 1). Over the entire study, trapping effort totalled 2423 trap nights. All captured animals were weighed, sexed and examined for signs of breeding, then released at the site of capture. Other species of small mammal that have ears large enough to receive a tattoo were also marked in the hope of detecting crossings of the fuelbreak by those species – Bush Rat, Rattus fuscipes, House Mouse and Agile Antechinus Antechinus agilis. The ears of the Eastern Pygmy Possum Cercartetus nanus, and Agile Antechinus (after March 2011) were considered too small to be marked by this method.

2.4 Radio-tracking Radio-transmitters were first attached to Smoky Mice in early October 2011. BD-2C transmitters (Holohil Systems Ltd.) fitted to a collar of plastic tubing (tygon) (Figure 7) were placed around the neck of eight Smoky Mice (Figure 8), three females, four males and one unsexed. An aerial of plastic-coated 25 lb fishing trace passed from the tube at the animal’s hindneck and extended rearwards along its dorsal surface. The entire transmitter package weighed 2.5 g. The location of radio-tagged animals was determined using a hand-held Yagi antenna connected to a 148-174 mhz telemetry receiver (Communication Specialists model R1000). The positions of radio-collared animals were determined as accurately as possible during night- time sessions lasting from shortly after dark to early morning and, once, from midnight until dawn. A study of activity patterns of captive Smoky Mice indicated that activity levels are relatively constant throughout the night (Woods and Ford 2000) so the timing of radio-tracking within the hours of darkness was not considered to be crucial.

8 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

Table 1. Field trips conducted during the investigation of the impacts of strategic fuelbreaks on the Smoky Mouse at Mt Terrible. Trip # Dates Primary activity Effort

1 10-13/5/2010 Exploratory trapping, marking of 60 trap nights, 5 survey cameras animals and deployment of survey cameras

2-3 1-29/6/2010 Deployment of survey cameras to 12 survey cameras further refine study sites

4 18-22/10/2010 Capture and marking of small 320 trap nights mammals adjacent to fuelbreak

5 22-26/11/2010 As above 549 trap nights

6 21-25/3/2011 As above 624 trap nights

7 11-15/4/2011 As above 315 trap nights

8 3-7/10/2011 Attachment of radio-collars 280 trap nights

9 17-21/10/2011 Radio-tracking and checking of radio- 20 trap nights collars

10 14-17/11/2011 As above 60 trap nights

11 21-25/11/2011 Radio-tracking and retrieval of radio- 111 trap nights collars

12 5-7/12/2011 Retrieval of radio-collars 84 trap nights

Night-time radio-tracking sessions were conducted by pairs of observers operating from a number of pre-arranged positions that were placed at intervals of approximately 50 m along the fuelbreak, over a total distance of about 300 m. Every 10-15 minutes each observer determined the direction of each radio-tagged animal as accurately as possible, using signal strength and a compass bearing. Particular care was taken to be certain about which side of the break each individual animal was on each time it was located. Often this involved walking along the break until the signal was coming from roughly perpendicular to the fuelbreak, so there could be no doubt. Observers then compared individual mouse locations to more accurately determine mice positions. The underground nesting locations of collared animals were also determined using radio-telemetry during the day (Figure 9) to confirm that animals were still in the area and to compare their position to radio-tracking data. Radio-signals were followed until it was apparent from the signal strength that stationary animals were within the vicinity of a few meters. The area was then briefly searched while avoiding undue disturbance, to locate a burrow entrance. This allowed targeted trapping to recapture collared animals. To check that the radio-collars were not causing injury, traps were set close to the daytime nests on nights when radio-tracking was not scheduled. Any captured, collared animals could then be examined in the hand for signs of abrasion or other possible damage caused by the collar. The condition of the collar was also checked at this time, and replaced if necessary.

9 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

Figure 7. Radio collar package used in this study (P. Macak).

Figure 8. Smoky Mouse with radio-collar attached (P. Menkhorst).

10 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

Figure 9. Radio-tracking to locate daytime nesting sites (P. Menkhorst). 3 Results 3.1 Trapping During the ten trapping sessions conducted throughout the study, a total of 33 Smoky Mice were captured and ear-tattooed (Table 2). These comprised 13 females, 17 males and 3 individuals whose sex could not be determined with confidence. A further two mice were captured but not marked at the time, though it is possible that they were marked later. Overall there were 102 Smoky Mouse captures. Of the 30 animals marked before the final trapping session, 10 were never recaptured and the remaining 20 were recaptured a total of 67 times (range 1-9). Three individuals were recaptured on the opposite side of the fuelbreak from where they were first trapped. This represents 10% of marked individuals and 4.4% of recaptures. Smoky Mice were captured on all traplines except the two placed at the highest elevations where the fuelbreak rejoins the Mt Terrible track (Figure 3, cover photograph) and the two lowest elevation traplines. This is despite Smoky Mice being detected at both the high elevation sites and at one of the two low elevation sites in the early stages of the study using survey cameras. Smoky Mouse trapping rates varied from 0 from some grids, to 16.7% when trap placement included targeting known nests. Exploratory and marking trapping (trips 1, 4-7) yielded a trap rate of 2.1%. Four other species were also trapped during the study: Agile Antechinus (25 individuals marked before March 2011 when this species was no longer tattooed), Eastern Pygmy Possum (not marked), Bush Rat (11 individuals), House Mouse (14 individuals). The Agile Antechinus was

11 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

captured on all trapping grids, the House Mouse only along the edge of the fuelbreak and only during spring, while the other two species were uncommon and localised. Table 2. Details of each Smoky Mouse captured and marked at Mt Terrible, 2010-2011 Animal # Date Sex Age at Times Trapped Date last Radio- Detected marked marking* recaptured on both captured collared on both sides? sides?

0-1 12/5/2010 ♀ Sub-ad 3 No 26/11/2010 0-2 12/5/2010 ♂ Sub-ad 9 Yes 15/4/2011 Yes 0-3 12/5/2010 ♀ Ad 0 - - 0-4 24/11/2010 ♂ Ad 1 No 26/11/2010 0-5 25/11/2010 ♂ Ad 0 - - 0-6 26/11/2010 ♀ Ad 0 - - 0-7 25/11/2010 ♂ Ad 0 - - 0-8 26/11/2010 ♀ Ad 8 No 21/10/2011 Yes # 1 No 0-9 26/11/2010 ♂ Ad 0 - - 1-0 24/3/2011 ♂ Sub-ad 1 No 25/3/2011 1-1 25/3/2011 ? Sub-ad 2 No 14/4/2011 1-2 25/3/2010 ? Sub-ad 3 No 21/10/2011 Yes # 3 Yes

1-3 13/4/2011 ♂ Ad 7 Yes 21/10/2011 Yes # 2 Yes 1-4 13/4/2011 ♂ Ad 4 No 21/10/2011 Yes # 4 Yes 1-5 13/4/2011 ? Ad 0 - -

1-6 14/4/2011 ♀ Ad 4 No 7/12/2011 Yes # 7 No 1-7 4/10/2011 ♂ Ad 5 Yes 25/11/2011 Yes # 6 Yes 1-8 4/10/2011 ♀ Ad 3 No 16/12/2011 1-9 4/10/2011 ♀ Sub-ad 3 No 21/10/2011 Yes # 5 Yes 2-0 21/10/2011 ♂ Ad 2 No 7/12/2011 Yes # 8 Yes 2-1 16/11/2011 ♂ Ad 2 No 24/11/2011 2-2 16/11/2011 ♀ Ad 2 No 24/11/2011 2-3 24/11/2011 ♀ Ad 0 - - 2-4 24/11/2011 ♀ Ad 0 - - 2-5 24/11/2011 ♂ Ad 1 No 6/12/2011 2-6 24/11/2011 ♂ Ad 2 No 7/12/2011 2-7 24/11/2011 ♀ Ad 1 No 6/12/2011 2-8 24/11/2011 ♀ Ad 3 No 7/12/2011 2-9 25/11/2011 ♂ Ad 0 - - 3-0 25/11/2011 ♂ Ad 0 - - 3-1 6/12/2011 ♂ Ad 1 No 7/12/2011 3-2 6/12/2011 ♂ Ad 0 - - 3-3 7/12/2011 ♀ Ad - - - *Ad = adult, Sub-ad = sub-adult

12 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

3.2 Radio-tracking Use of radio-telemetry greatly increased the rate of detection of fuelbreak crossings by Smoky Mice, although movement data could only be collected during the night from five of the eight animals fitted with collars. This technique also allowed us to locate the daytime nest sites of radio- collared animals. Thirteen (72%) of the 18 animal-nights of tracking resulted in the detection of an animal crossing the fuelbreak (Table 3). Four animals were tracked for three consecutive nights, after which their collars came off, while one animal was tracked for a total of 6 nights. Two animals, which shared a daytime nest on the west side (animals 1-3 and 1-4), crossed to the east side of the break on every night they were tracked. The only female tracked (animal 1-9), that nested with the two animals above, is known to have crossed on only one night. The animal that was tracked over the most nights (animal 1-7) crossed over on four of the six nights it was tracked. Data collected during the radio-tracking sessions roughly indicated at what time of the night animals were crossing, which varied among individuals (Table 4). An additional collared animal (2-0) was also detected on both sides of the fuelbreak after being trapped on the west side, found at a nest location the next morning on the east side then subsequently trapped back on the west side. The information we were able to gain through radio-tracking was severely curtailed by problems with transmitters or their attachment. The transmitters attached to animals 0-8 and 2-0 failed sometime between the few days after their collars were fitted and when the next radio-tracking session began. Both of these animals were later recaptured and the collars, which showed evidence of damage to the transmitter itself, were removed. The collars of animals 1-2, 1-3, 1-4 and 1-9 were found on the ground; three on the fuelbreak, and one nearby, seemingly having become detached some time between 20 October and 15 November 2011. The collars were intact, showing no signs that explained why or how they may have come off. These four animals were not recaptured subsequent to their collars being found. The collar on animal 1-6 also became detached before crossing data could be collected and was found caught on a twig six days after it was originally fitted. This animal was later recaptured. Several collars needed to be replaced as the plastic tubing was damaged, seemingly by the Smoky Mice themselves, chewing on each others’ collars. Attached collars did not appear to cause any damage to the animals themselves. Radio signals detected during tracking varied in their quality, with precise signal direction able to be determined with confidence some of the time, but not always. For example, a strong signal was sometimes detected over a broad arc, making it difficult to determine a precise direction. Signals also changed from weak to strong in an erratic manner, as often occurs when animals are moving about, also making it difficult on those occasions to determine a precise direction. Despite these difficulties we were able to ascertain the locations of mice within a level of accuracy (estimated to be a 50-100 m wide area in front of a radio-tracking point) that was enough to determine the general whereabouts of individuals, including which side of the break they were on.

13 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

Table 3. Numbers of detected fuelbreak crossings by radio-collared Smoky Mice. Figures are a combination of location data from night-time tracking sessions and daytime positions when nesting. Shading shows groupings of animals according to nest site.

Session 1 Session 2 Session 3

Animal # 17/10 18/10 19/10 15/11 16/11 22/11

1-7 0 2 0 2 2 3 1-2 0 2 2 1-3 2 2 2 collars dropped 1-4 2 2 2 1-9 0 2 0

Table 4. Locations of radio-tagged Smoky Mice during night-time tracking sessions in relation to the daytime nest site used the day before. e = east, w = west

Date Time Animal and Crossed Notes sex fuelbreak?

17/10/2011 2105 1-2 (?); 1-7 (♂) no On e. side of break, same side as day nest

2313 1-3 (♂); 1-4 (♂) yes On e. side of break, had crossed from day nest

2315 1-9 (♀) no On w. side, same side as day nest

18/10/2011 2130- 1-2 (?); 1-7 (♂) no On e. side, same side as day nest 2215

2230 1-2 (?); 1-7 (♂) yes On w. side, had crossed from day nest

2300 1-3 (♂); 1-4 yes On e. side, had crossed from day nest (♂); 1-9 (♀)

0021 1-2 (?); 1-7 (♂) yes On e. side, had crossed back since 2230 hrs

19/10/2011 2155 1-4 (♂) yes On e. side, had crossed from day nest

1-3 (♂); 1-9 (♀) no On w. side, same side as day nest

2300 1-3 (♂) yes On e. side, had crossed since 2155 hrs

2345 1-2 (?); 1-7 (♂) no On e. side, same side as day nest

0100 1-2 (?) yes On w. side, had crossed since 2345 hrs

15/11/2011 0000- 1-2 (?); 1-7 (♂) yes Remained on w. side, had crossed from day 0400 nest but collar from 1-2 later found on edge of break

16/11/2011 2230- 1-7 (♂) yes On w. side, had crossed from day nest after 2340 moving around on e. side for 1.5 hrs

22/11/2011 1-7 (♂) yes Crossed from w. to e. to w. sides over a period of 2 hrs

14 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

We located a total of five nest burrows (Figure 3), two vertical burrows (Figure 10) on the relatively flat area between Mt Terrible Track and the fuelbreak, one sloping burrow beneath the root clump of a fallen tree on the east side of the fuelbreak, and two others on steep, shaly slopes, one on the east and the other to the west of both the fuelbreak and the Mt Terrible Track. The burrow entrances of the latter two nest sites were not actually located amongst the rocky surface, but it was clear that the animals were close by. Up to three collared animals, of either sex, shared the same nest hole on some days and trapping results suggest that other un-collared individuals were also sharing burrows with collared animals.

Figure 10. Entrance to Smoky Mouse nest hole, Mt Terrible, October 2011 (P. Menkhorst).

15 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

4 Discussion 4.1 Movements revealed by trapping and radio-tracking Our capture-mark-recapture study succeeded in establishing that Smoky Mice will cross the fuelbreak at this site. All three animals from the trapped sample that were found to have crossed the fuelbreak were males. The radio-tracking study, in comparison, showed that crossings of the fuelbreak by both sexes were regular, and seemingly routine, during the study period at this site. The radio-tracking component took place during the breeding season of the mice (Cockburn 1981, Ford et al. 2003, authors unpublished data) when males may be more inclined to wander, however, females were also shown to have crossed the fuelbreak. Rates of crossing for females were lower than for males, but our sample of locations for females was low because the loss of, and damage to, transmitters reduced the number of female animal-nights of tracking. The radio transmitters were effective for determining the general whereabouts (within 50-100 m) of radio-tagged individuals at night and allowed precise locations of daytime nests to be determined. As this level of accuracy was sufficient for the needs of the study we did not attempt to process the data further to plot night locations at a finer scale. We suspect that this may prove to be difficult because of the broad arc over which many of the radio signals could be detected. We are unsure whether this is a characteristic of the transmitters used, or resulted at least partly from signal bounce in the complex environment with hard surfaces such as large trees, log piles, sloping bare ground and rocks. The main problem with the radio-transmitter package was the rate at which they become detached from the host animal, reducing the number of individual animals that could be tracked and limiting the amount of information gained. Five of the eight radio-collars were found lying on the surface, including three on the fuelbreak itself. We do not know the cause of this premature detachment and the transmitter packages provided no clues – for example, there were no signs of damage that might have been attributed to a predator. The collars may have been too loose and able to slip forward over the animal’s head – caused by our reticence to adequately tighten the collar during attachment out of concern for the animal’s welfare. At least one of the collars appeared to have been caught on a twig. Alternatively, the animals may have been taken by a predator and the collars discarded. This seems particularly likely in the cases where the transmitter was found on the fuelbreak, an unlikely place for a Smoky Mouse to spend time working at removing a loose collar. Further, these three animals were not recaptured. Potential mammalian predators include the Spot-tailed Quoll Dasyurus maculatus, Red Fox Vulpes vulpes and House Cat Felis catus, However, we neither saw nor heard evidence of any of these species at the site, day or night, apart from finding a single fox scat on the fuelbreak, and they were not detected on any of our survey cameras. It is unclear whether the Powerful Owl Ninox strenua and Southern Boobook Ninox novaeseelandiae were present at the site. In addition, the discarded collars where not damaged, as might be expected if predators were involved. Despite these difficulties, we succeeded in obtaining clear evidence of tagged animals regularly crossing the fuelbreak.

4.2 Likely impacts of the fuelbreak on population processes Our results suggest that the fuelbreak is unlikely to cause long-term partitioning of populations of Smoky Mice that inhabited the area prior to its construction. We detected Smoky Mice moving across the fuelbreak and back again during a single night, and others that moved from one nest to another, remaining on the opposite side of the fuelbreak the following day. In addition, one individual was shown to have crossed the Mt Terrible Track which also involved negotiating a steep embankment where the Mt Terrible Track is incised into the hillside. These observations

16 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

indicate that there is no detectable barrier effect due to the fuelbreak. Accordingly, a change to population status resulting from reduced gene flow or reduced population number would seem unlikely. Consequently we have not investigated any habitat manipulations aimed at alleviating barrier effects. That is not to say that the fuelbreak has no negative effect on the Smoky Mouse population. Construction of the break removed habitat and therefore potentially reduced the local population size. It seems likely that any barrier effect would have been greatest in the year following construction, before low vegetation cover had developed on the verges of the fuelbreak (see Figure 4), thereby reducing its effective width for small animals such as the Smoky Mouse. This study was conducted between 17 and 30 months after construction and so would have missed any initial impact that occurred immediately after construction. It is also probable that animals are exposed to an increased risk of predation while crossing the fuelbreak which does not provide the same level of cover, in the form of dense, low vegetation and coarse woody debris, as does the surrounding forest. However, this study was not designed to investigate survivorship before and after construction, and the question of increased rates of predation following construction of the fuelbreak remains unresolved. It is possible that maintaining low vegetation cover (say, 0.5 m) within the verges of the fuelbreak would reduce predation rates, or even facilitate crossings.

4.3 Trapping rates Low rates of capture (< 5%) are the norm for the Smoky Mouse when standard box traps, such as Elliott type A traps, or wire mesh cage traps, are deployed for short periods, although they can be locally higher (e.g. 12% at Mt William, Grampians National Park) (Menkhorst and Seebeck 1981, Ford et al. 2003). Based on surveys using these techniques, populations of Smoky Mice have been considered to be sparse, localised and ephemeral (Menkhorst 1996, Menkhorst and Broome 2008b). However, the recent deployment of animal-triggered cameras as an alternative detection technique has resulted in a greatly increased rate of detecting Smoky Mice (Nelson et al. 2010, authors unpublished data), suggesting that the species is not as uncommon or restricted as previously thought. Further, Smoky Mice have been detected at the study site during three separate studies spanning 25 years (Lumsden et al. 1991, Nelson et al. 2010, this study), so the population at this site appears to be relatively stable.

4.4 Other natural history information gleaned from the study The information we gained on Smoky Mouse nest burrows broadly conforms to observations reported by Woods and Ford (2000) and Ford et al. (2003). The construction of burrow systems seems to be a characteristic of the genus Pseudomys (Breed and Ford 2007). Further, our observations of burrow occupation by multiple individuals of both sexes, and swapping of burrows between nights, suggest that the Smoky Mouse is a communal, plural breeder, as also suggested by Woods and Ford (2000).

17 Investigation of the barrier effects of a strategic fuelbreak on a population of the Smoky Mouse at Mt Terrible, Victoria

References Breed, B. and Ford, F. 2007. Native Mice and Rats. Australian Natural History Series, CSIRO Publishing, Melbourne. Cockburn, A. 1981. Population regulation and dispersion of the Smoky Mouse, Pseudomys fumeus II. Spring decline, breeding success and habitat heterogeneity. Australian Journal of Ecology 6: 255-266. Ford, F., Cockburn, A. and Broome, L. 2003. Habitat preference, diet and demography of the Smoky Mouse, Pseudomys fumeus (Rodentia: Muridae), in south-eastern New South Wales. Wildlife Research 30: 89-101. Lumsden, L.F., Alexander, J.S.A., Hill, F.A.R., Krasna, S.P. and Silveira, C.E. 1991. The vertebrate fauna of the Land Conservation Council Melbourne – 2 Study Area. Arthur Rylah Institute for Environmental Research Technical Report Series Number 115. Flora and Fauna Division, Department of Conservation and Environment, Heidelberg, Victoria. Menkhorst, P.W. (Ed). 1996. Mammals of Victoria: Distribution, ecology and conservation. Revised paperback edition. Oxford University Press, Melbourne. Menkhorst, P. and Broome, L. 2008a. National Recovery Plan for the Smoky Mouse, Pseudomys fumeus. Department of Sustainability and Environment, Melbourne. Menkhorst, P. and Broome, L. 2008b. Background and Implementation Information for the Smoky Mouse Pseudomys fumeus National Recovery Plan. Department of Sustainability and Environment, Melbourne. Menkhorst, P. and Knight, F. 2011. A Field Guide to the Mammals of Australia. Third edition. Oxford University Press, Melbourne. Menkhorst, P.W. and Seebeck, J.H. 1981. The status, habitat and distribution of Pseudomys fumeus Brazenor (Rodentia: Muridae). Australian Wildlife Research 8: 87-98. Nelson, J., Menkhorst, P., Howard, K., Chick, R. and Lumsden, L. 2010. The Status of Smoky Mouse populations at some historic Sites in Victoria, and survey methods for their detection. Arthur Rylah Institute for Environmental Research Unpublished Report number 2009/17. Department of Sustainability and Environment, Heidelberg, Victoria. Woods, R.E. and Ford, F.D. 2000. Observations of the behaviour of the Smoky Mouse Pseudomys fumeus (Rodentia: Muridae). Australian Mammalogy 22: 35-42.

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