Arid Recovery Reserve Research Articles

Rapid change in anti‐predator behaviour of a threatened marsupial after thousands of years of isolation from predators

AbstractPrey naivety occurs when an animal does not recognize or is unable to respond effectively to the threat of a predator. Many animals lose their anti‐predator responses if they become isolated from predators, becoming vulnerable to increased predation rates if released into areas where native or introduced predators are present. In situ exposure to introduced predators is a technique that has been shown to improve anti‐predator traits in burrowing bettongs (Bettongia lesueur) and greater bilbies (Macrotis lagotis) and is associated with greater survival in bilbies. However, little is known about how in situ exposure to native predators can address the issue of prey naivety. This study investigated whether Shark Bay bandicoots (Perameles bougainville) from a remnant island population isolated from all mammalian predators for several thousand years could improve their anti‐predator behaviour after living with a native predator, the western quoll (Dasyurus geoffroii). We compared the vigilance and wariness behaviour, and nest site attributes of bandicoot populations living with and without native quolls at the Arid Recovery Reserve in South Australia. We found that after 6 years of quoll exposure, quoll‐exposed bandicoots had significantly larger flight initiation distances and spent more time engaged in vigilance behaviours at feed trays compared to control bandicoots. Quoll‐exposed bandicoots also selected nests with increased vegetation cover, preferring nests with both understory and overstory shrub cover present. The results of this study indicate that in situ exposure to native predators can improve vigilance and wariness behaviours in Shark Bay bandicoots over relatively short time frames. Exposing threatened species to native predators may assist with preparing them for life outside fenced safe havens.

Potential effects of arid shrubland degradation on habitat suitability for a declining arid zone bird, the Chestnut‐rumped Thornbill (Acanthiza uropygialis)

AbstractAustralia's arid shrublands have been impacted by a variety of threatening processes since European settlement, and changes to ecosystem structure and function have been observed at multiple levels. The lack of recruitment and regeneration of the perennial shrub and tree layer in these communities has implications for many shrubland birds, including species of conservation concern such as the Chestnut‐rumped Thornbill (Acanthiza uropygialis: Acanthizidae). We documented foraging behaviour and habitat selection of the Chestnut‐rumped Thornbill at the Arid Recovery Reserve in South Australia and surveyed vegetation characteristics within the Reserve and in an adjacent pastoral property. We found that Chestnut‐rumped Thornbills preferentially use certain plant species: Callitris glaucophylla, Acacia aneura, Acacia ligulata and Acacia tetragonophylla, and that these species were significantly less abundant at our study sites outside the Reserve than inside. Major differences in the structure and composition of the vegetation inside and outside the Reserve suggest that changes in habitat structure and composition occurring in the broader landscape (outside the fenced area) decrease the suitability of arid shrubland habitat for the Chestnut‐rumped Thornbill and may contribute to their absence in unprotected areas. Our study indicates that deterioration of the perennial shrub layer could have significant consequences for the persistence of the Chestnut‐rumped Thornbill in arid rangelands. Our findings highlight the importance of rangeland management and restoration of Australia's arid shrublands in preventing declines of the Chestnut‐rumped Thornbill and other insectivorous birds.

Seroprevalence of

Toxoplasma gondii is a ubiquitous protozoan transmitted by felids and infection, morbidity, and mortality occur in numerous marsupial species. This study explores the relationship between cat exposure and Toxoplasma in burrowing bettongs (Bettongia lesueur) in the Arid Recovery Reserve (ARR), South Australia. We estimated seroprevalence, using a modified agglutination test for T. gondii-specific immunoglobulins, in cat-free and cat-exposed bettong populations. Tissue samples collected opportunistically from bettong carcasses and from cats within and around the reserve were screened for T. gondii DNA using multiplex real-time polymerase chain reaction (M-qPCR). Two cats trapped inside the ARR tested positive (50.0%; 95% CI: 15.0–85.0%). All bettongs tested from the cat-free (n = 48) and cat-exposed (n = 19) exclosures were seronegative (95% CI: 0–7.41% and 0–16.82% respectively). We found no evidence of fatal toxoplasmosis, with all bettong carcasses negative on M-qPCR (n = 11). We propose that T. gondii was not detected in bettongs coexisting with cats primarily due to low exposure of bettongs at the time of sampling, possibly due to poor oocyst viability in arid conditions or low shedding by cats. Ongoing screening throughout high and low rainfall years should be conducted to better establish the risk of Toxoplasma to bettongs in the ARR.

Understanding dispersal patterns can inform future translocation strategies: A case study of the threatened greater stick‐nest rat (Leporillus conditor)

AbstractDispersal behaviour and sociality are significant factors influencing survival at both the individual and population levels. In translocation and breeding programmes, social structure and sex‐biased philopatry and dispersal should be considered in order to maximise population viability and conservation outcomes. Here, we use the greater stick‐nest rat (Leporillus conditor), a native Australian rodent, as a case study to understand how knowledge of social structure and dispersal can inform conservation and translocation programmes. We combine high‐throughput DNA sequencing with field trapping data from a translocated population of greater stick‐nest rats at Arid Recovery Reserve, South Australia, to provide the first empirical evidence of female philopatry and male‐biased dispersal in this species. Males were found to disperse, on average, 1.5 km from the natal nest, while females typically did not disperse beyond 500 m. Further, recapture data showed that females demonstrated a higher degree of nest fidelity than males over time. Based on these findings, we make two key recommendations for future translocations of the species. Firstly, founders should be harvested in small groups at adjacent nest sites with groups separated by a minimum of 1.5 km allowing family group structure to be retained during translocation while simultaneously maximising genetic diversity. Secondly, translocated individuals should be released in family cohorts into patches of optimal habitat that contain adequate shelter substrates interspersed over short distances (~300–500 m, the maximum dispersal distance of females found in this study), thereby facilitating nest establishment and maintenance of family groups. The results of this study have implications for conservation and reintroduction biology as a whole; we highlight the importance of considering spatial genetic structure during all stages of translocations to improve outcomes, and the value of combining genetic and field data to better understand species’ social and spatial preferences.

Female reproductive suppression in an Australian arid zone rodent, the spinifex hopping mouse

AbstractThe spinifex hopping mouse (Notomys alexis) is an Australian arid zone rodent that undergoes boom and bust population cycles in its natural environment. Most populations studied to date have been sympatric with exotic predators and introduced herbivores, likely affecting their population dynamics. Therefore, it is unclear whether high‐density populations of hopping mice are regulated by purely extrinsic factors or whether intrinsic factors are also at play. We hypothesized that reproductive suppression of female N. alexis may occur in high‐density populations as has been observed in some other rodent species. Reproductive condition of adult female N. alexis was compared between a high‐density population within the Arid Recovery reserve, where exotic predators and introduced herbivores are excluded, and a low‐density population on adjacent pastoral properties (no exclusions). Trap success was 10 times higher inside the reserve than at pastoral sites, and no adult females were observed breeding in the reserve population, despite 26 % of females at pastoral sites recorded breeding. Our results indicate that adult female N. alexis in the high‐density reserve population were reproductively suppressed, but the similar sex ratios in both populations and the high female body mass and body condition in the reserve indicated that this was not due to demographic differences between the two populations or food scarcity. Our study indicates that the ‘busts’ observed in arid zone rodent populations may be amplified due to the presence of exotic predators and/or grazing by introduced herbivores. We contend that prior to the introduction of exotic predators and introduced herbivores in Australia, the arid zone rodent N. alexis would likely have been more abundant and intrinsic population regulation through female reproductive suppression may have played a larger role in population regulation.

Long-term genetic consequences of mammal reintroductions into an Australian conservation reserve

Reintroduction programs aim to restore self-sustaining populations of threatened species to their historic range. However, demographic restoration may not reflect genetic restoration, which is necessary for the long-term persistence of populations. Four threatened Australian mammals, the greater stick-nest rat (Leporillus conditor), greater bilby (Macrotis lagotis), burrowing bettong (Bettongia lesueur) and western barred bandicoot (Perameles bougainville), were reintroduced at Arid Recovery Reserve in northern South Australia over the last 18years. These reintroductions have been deemed successful based on population growth and persistence, however the genetic consequences of the reintroductions are not known. We generated large single nucleotide polymorphism (SNP) datasets for each species currently at Arid Recovery and compared them to samples collected from founders. We found that average genetic diversity in all populations at the Arid Recovery Reserve are close to, or exceeding, the levels measured in the founders. Increased genetic diversity in two species was achieved by admixing slightly diverged and inbred source populations. Our results suggest that genetic diversity in translocated populations can be improved or maintained over relatively long time frames, even in small conservation reserves, and highlight the power of admixture as a tool for conservation management.

Rewilded mammal assemblages reveal the missing ecological functions of granivores

Abstract Rewilding is a strategy for ecological restoration that uses reintroductions of animals to re‐establish the ecological functions of keystone species. Globally, rewilding efforts have focused primarily on reinstating the ecological functions of charismatic megafauna. In Australia, rewilding efforts have focused on restoring the ecological functions of herbivorous and omnivorous rodents and marsupials weighing between 30 and 5,000 g inside of predator‐proof exclosures. In many arid ecosystems, mammals are considered the dominant seed predators. In Australian deserts, ants are considered to be the primary removers and predators of seeds and mammals unimportant removers and predators of seeds. However, most research on granivory in Australian deserts has occurred in areas where native mammals were functionally extinct. Here, we compare rates of seed removal by mammals and ants on shrub seeds and abundance of shrub seedlings in two rewilded desert ecosystems (Arid Recovery Reserve and Scotia Wildlife Sanctuary) with adjacent areas possessing depauperate mammal faunas. We used foraging trays containing seeds of common native shrubs (Acacia ligulata and Dodonaea viscosa) to examine rates of seed removal by ants and mammals. We quantified the abundance of A. ligulata and D. viscosa seedlings inside and outside of rewilded areas along belt transects. By excluding ants and mammals from foraging trays, we show that ants removed more seeds than mammals where mammal assemblages were depauperate, but mammals removed far more seeds than ants in rewilded areas. Shrub seedlings were more abundant in areas with depauperate mammal faunas than in rewilded areas. Our study provides evidence that rewilding of desert mammal assemblages has restored the hitherto unappreciated ecological function of omnivorous rodents and bettongs as seed predators. We hypothesize that the loss of omnivorous mammals may be a factor that has facilitated shrub encroachment in arid Australia. We contend that rewilding programs aimed at restoring ecological processes should not ignore consumers with relatively lower per capita consumptive effects. This is because consumers with low per capita consumptive effects often occur at high population densities or perform critical ecological functions and thus may have significant population level impacts that can be harnessed for ecological restoration. A plain language summary is available for this article.

Predator exposure improves anti‐predator responses in a threatened mammal

Abstract Incorporating an understanding of animal behaviour into conservation programmes can influence conservation outcomes. Exotic predators can have devastating impacts on native prey species and thwart reintroduction efforts, in part due to prey naïveté caused by an absence of co‐evolution between predators and prey. Attempts have been made to improve the anti‐predator behaviours of reintroduced native prey by conducting laboratory‐based predator recognition training but results have been varied and have rarely led to improved survival in reintroduction programmes. We investigated whether in situ predator exposure could improve anti‐predator responses of a predator‐naïve mammal by exposing prey populations to low densities of introduced predators under controlled conditions. We reintroduced 352 burrowing bettongs to a 26‐km2 fenced exclosure at the Arid Recovery Reserve in South Australia and exposed them to feral cats (density 0.03–0.15 cats/km2) over an 18‐month period. At the same time, we translocated a different group of bettongs into an exclosure free of introduced predators, as a control. We compared three behaviours (flight initiation distances, trap docility and behaviour at feeding trays) of cat‐exposed and control bettongs before the translocations, then at 6, 12 and 18 months post‐translocation. Cat‐exposed bettongs displayed changes in behaviour that suggested increased wariness, relative to control bettongs. At 18 months post‐reintroduction, cat‐exposed bettongs had greater flight initiation distances and approached feed trays more slowly than control bettongs. Cat‐exposed bettongs also increased their trap docility over time. Synthesis and applications. Translocation is recommended as a conservation tool for many threatened species yet success rates are generally low. We demonstrate that controlled levels of in situ predator exposure can increase wariness in the behaviour of naïve prey. Our findings provide support for the hypothesis that in situ predator exposure could be used as a method to improve the anti‐predator responses of predator‐naïve threatened species populations.

Vegetation damage caused by high densities of burrowing bettongs (Bettongia lesueur) at Arid Recovery

Burrowing bettongs (Bettongia lesueur) reached high densities within the fenced Arid Recovery reserve. Grazing pressure was assessed by comparing the vegetation inside and outside the reserve during April in 2012, 2013 and 2014. Mean numbers of bettong tracks crossing small 10 m × 1 m plots overnight in the main exclosure were 20 in 2012, decreasing to 4 in 2013 and 3 in 2014. Similar declines were present in the second expansion, where tracks decreased from 7 in 2012 to 3 in 2013 and 2 in 2014. Perennial plant species richness decreased significantly over the study period. Acacia aneura, Acacia ligulata, Atriplex vesicaria, Crotalaria eremaea, Dodonaea viscosa, Enchylaena tomentosa, Maireana astrotricha and Sida ammophila were the most heavily grazed species within the reserve. Overall, more than 25% of plants showed some form of conspicuous grazing. C. eremaea and E. tomentosa showed little damage outside the reserve. Inside the reserve many C. eremaea were dead and heavily browsed and few E. tomentosa remained. Recent recruitment of A. ligulata and D. viscosa was also much higher outside the reserve. High densities of burrowing bettongs were associated with declines in vegetation condition potentially impacting other species and the ecosystem as a whole.

Improved technique for capturing the greater bilby (Macrotis lagotis) using burrow cage traps

The greater bilby (Macrotis lagotis) is generally trap shy and uninterested in baits, therefore difficult to capture. In order to capture an entire population of bilbies in the Arid Recovery Reserve of central South Australia, we developed an improved method of using burrow cage traps. Traps were set to engulf the entrance of the burrow and the base was camouflaged with sand. We obtained a very high capture rate (6% overall, and 73% for confirmed burrows). Assuming that occupied burrows can be detected, this method should improve capture rates for this endangered and cryptic species.

Predation determines the outcome of 10 reintroduction attempts in arid South Australia

Ten reintroduction attempts were conducted in and around the Arid Recovery Reserve in northern South Australia between 1998 and 2008. Five locally-extinct mammal species and one reptile species were reintroduced into a fenced Reserve where cats, foxes and rabbits were excluded. Reintroductions of the nationally threatened greater stick-nest rat, burrowing bettong, greater bilby and western barred bandicoot were all considered successful based on short and medium-term success criteria. These criteria included continued survival after 8years, increased distribution across the large Reserve and, most importantly, recovery after a drought event. The trial reintroductions of the numbat and woma python into the Reserve were unsuccessful due to predation by native avian and reptilian predators respectively. Outside the Reserve, where cats and foxes were present but controlled through poison baiting, reintroduction attempts of the greater bilby and burrowing bettong were unsuccessful. High mortality was attributed to cat and fox predation with dingoes also contributing to post-release mortality in bettongs. However, a reintroduction of burrowing bettongs into a fenced area with low rabbit and cat abundance has, to-date, met short-term and medium-term success criteria. Results suggest that the absence or severe restriction of exotic mammalian predators was the critical factor responsible for the success of the mammal reintroductions. Determining thresholds of predator activity below which successful reintroduction of threatened species can occur, are needed to improve the science of reintroduction biology in Australia.

Predation by snakes thwarts trial reintroduction of the Endangered woma pythonAspidites ramsayi

AbstractCase studies of well-documented snake reintroductions are limited, despite their potential value for conservation and ecosystem recovery. The Endangered womaAspidites ramsayiis a large boid snake that has declined considerably and is now threatened throughout much of central Australia. We describe a trial release of captive-bred womas into the feral predator-free Arid Recovery Reserve in northern South Australia. All of the reintroduced womas were killed within 4 months, with predation by the mulga snakePseudechis australisconfirmed or implied in all cases. Lessons learned for the conditioning of captive-bred snakes for wild release and the role of the mulga snake in structuring Australian arid-zone snake assemblages are discussed.

Eradication of rabbits from landscape scale exclosures: pipedream or possibility?

Summary High densities of the European Rabbit (Oryctolagus cuniculus) were eradicated from 60 km2 of the Arid Recovery Reserve between 1996 and 2001. Eradication was possible due to an initial knockdown caused by rabbit haemorrhagic disease, followed by effective exclusion fencing, broadscale poison baiting, targeted shooting, warren destruction and trapping on rabbit burrows and buckheaps. The efficacy of different broadscale control and intensive rabbit eradication techniques was subsequently estimated in a 26 km2 expansion to the Reserve from 2002 to 2006. Non-target implications of these control techniques were also assessed where possible. An estimated 8000 rabbits were removed in total from both areas and results suggest that rabbit eradication is possible at a landscape scale. Strategies for eliminating rabbits from confined areas are suggested.

Relative impacts of cattle grazing and feral animals on an Australian arid zone reptile and small mammal assemblage

AbstractThe effect of different levels of cattle grazing on an arid Australian small terrestrial mammal and lizard assemblage was assessed in a long‐tem series of cross‐fence comparisons. Cross‐fenced sites were closely matched for edaphic and vegetation characteristics and experienced near identical weather patterns, to ensure that cattle grazing pressure was the principal determinant of any differences in fauna assemblages. In addition, the effects of removal of cattle, cats, foxes and rabbits from three of these long‐term monitoring sites were assessed to determine the relative impacts of cattle grazing and feral animals. Small mammal captures, with the exception of Mus musculus, revealed a significant negative response to cattle grazing pressure but this response was of a considerably lower magnitude than the dramatic increase in rodent captures and species richness within the feral animal‐proof Arid Recovery Reserve. Higher kangaroo numbers in ungrazed controls, compared with treatments grazed by cattle, possibly negated the benefits to small mammals of removing cattle grazing. No reptile species responded significantly to the grazing treatments although reptile richness and captures of geckos and skinks were the lowest and agamid captures were the highest at heavily grazed sites. Nephrurus levis was the only reptile species to increase significantly, while captures of some smaller geckoes declined, within the feral‐proof treatment. Feral predation exerted a more significant effect on most small mammal species than the levels of cattle grazing assessed in this study, yet reptile responses to grazing or feral animals were less apparent and were likely primarily driven by changes in vegetation cover or secondary trophic impacts.

Arid Recovery – A comparison of reptile and small mammal populations inside and outside a large rabbit, cat and fox‐proof exclosure in arid South Australia

AbstractAustralian arid zone mammal species within the Critical Weight Range (CWR) of 35 g–5.5 kg have suffered disproportionately in the global epidemic of contemporary faunal extinctions. CWR extinctions have been attributed largely to the effects of introduced or invasive mammals; however, the impact of these threatening processes on smaller mammals and reptiles is less clear. The change in small mammal and reptile assemblages after the removal of rabbits, cats and foxes was studied over a 6‐year period in a landscape‐scale exclosure in the Australian arid zone. Rodents, particularly Notomys alexis and Pseudomys bolami, increased to 15 times higher inside the feral‐proof Arid Recovery Reserve compared with outside sites, where rabbits, cats and foxes were still present. Predation by cats was thought to exert the greatest influence on rodent numbers owing to the maintenance of the disparity in rodent responses through dry years and the differences in dietary preferences between rabbits and P. bolami. The presence of introduced Mus domesticus or medium‐sized re‐introduced mammal species did not significantly affect resident small mammal or reptile abundance. Abundance of most dasyurids and small lizards did not change significantly after the removal of feral animals although reductions in gecko populations inside the reserve may be attributable to second order trophic interactions or subtle changes in vegetation structure and cover. This study suggests that populations of rodent species in northern South Australia below the CWR may also be significantly affected by introduced cats, foxes and/or rabbits and that a taxa specific model of Australian mammal decline may be more accurate than one based on body weight.

Trial translocation of the numbat (Myrmecobius fasciatus) into arid Australia

Five numbats (Myrmecobius fasciatus) were transferred into the Arid Recovery Reserve in November 2005 as part of a trial to investigate the suitability of the reserve for a full-scale reintroduction of M. fasciatus. Mean home ranges in this study were 67 ha in summer and 25 ha in autumn/winter. This is similar to home ranges of M. fasciatus at other locations. M. fasciatus used burrows despite available log habitat and were active in air temperatures of 21−30°C and soil temperatures of 21−42°C during the autumn/winter period. M. fasciatus used ‘mulga’, ‘sanddune vegetation’, ‘bullock bush’ and ‘cypress pine’ more often than ‘saltbush/bluebush’ and other available habitats. They were also found more extensively on ‘dunes’ or ‘sand plain’ landforms than on ‘swales’. Two males were still alive 18 months after release; the other three were taken by an unknown bird of prey. We suggest that another trial be undertaken with a larger sample size to determine whether females are able to wean young and whether Arid Recovery is able to sustain a viable population of M. fasciatus.

The effects of browsing by feral and re-introduced native herbivores on seedling survivorship in the Australian rangelands

Browsing by introduced cattle (Bos taurus) and rabbits (Oryctolagus cuniculus) can limit the recruitment of some arid zone tree and shrub species. In a study conducted at the Arid Recovery Reserve, Roxby Downs, SA, we aimed to quantify initial recruitment changes in shrubs after the removal of cattle and rabbits and the re-introduction of locally extinct fauna. The presence and abundance of seedlings was measured at groves of seven native perennial shrubs over 6 years under four browsing treatments: (1) ‘reserve-reintroductions’ [re-introduced greater stick-nest rats (Leporillus conditor), burrowing bettongs (Bettongia lesueur) and greater bilbies (Macrotis lagotis)], (2) ‘reserve-no browsers’, (3) ‘pastoral-stocked’ (rabbits and cattle), and (4) ‘pastoral-destocked’ (rabbits). Recruitment of mulga (Acacia aneura F.Muell. ex Benth.), silver cassia (Senna artemisioides subsp. petiolaris Randell) and sandhill wattle (Acacia ligulata A.Cunn. ex Benth.) was significantly greater in the two browsing regimes inside the Reserve than in the two pastoral regimes. The number of recruits of these three species declined at ‘pastoral-destocked’ and ‘pastoral-stocked’ sites but increased at ‘reserve-reintroductions’ and ‘reserve-no browsers’ sites from 2001 to 2006. Narrow-leaf hopbush (Dodonaea viscose (L.) Jacq.) showed a trend towards increased recruitment at sites in both browsing regimes inside the Reserve, but decreased recruitment at sites in both pastoral regimes. Native plum (Santalum lanceolatum R.Br.), native apricot (Pittosporum phylliraeoides orth. var. DC.) and bullock bush (Alectryon oleifolius (Desf.) S.T.Reynolds) exhibited no significant difference in recruitment between the four browsing regimes within the study timeframe. These results suggest that excluding rabbits and stock may benefit the germination and survival of mulga, silver cassia and sandhill wattle. To date, re-introduced native herbivores at low numbers have not been found to negatively affect the recruitment or growth rate of the seven perennial plant species studied.

Ecological roles of rabbit, bettong and bilby warrens in arid Australia

Burrows created by other organisms provide important refugia for many vertebrates and invertebrates. With severe range declines of most of Australia's burrowing mammals, the introduced European rabbit may have replaced the role of native burrowers. The vertebrate and invertebrate fauna using the warrens of the native burrowing bettong and greater bilby were compared with fauna using warrens of the introduced European rabbit and control sites without active warrens in arid South Australia. Echidnas, broad-banded sandswimmers, hemipterans and coleopterans, particularly Brises caraboides, revealed a preference for warrens over sites without warrens. Iridomryrmex sp. E ( rufoniger gp.) was recorded at significantly higher abundance at bettong rather than rabbit warrens and Melophorus ants apparently benefited from the bare ground around warrens of both native burrowers and rabbits. Identification of small mammal preferences for different warren types was confounded by low predation rates inside the Arid Recovery Reserve, where cats and foxes had been exterminated to allow reintroduction of native burrowers. Due to the widespread use of the below ground and surface features of warrens by commensal native vertebrates and invertebrates, consideration should be given to reintroducing native burrowers following the removal of rabbits in arid Australia.

Diets of the re-introduced greater bilby (Macrotis lagotis) and burrowing bettong (Bettongia lesueur) in the Arid Recovery Reserve, Northern South Australia.

The diets of re-introduced populations of the greater bilby (Macrotis lagotis) and burrowing bettong (Bettongia lesueur) were compared in arid South Australia. Scats were collected during five sampling periods over 15 months and dietary items were usually identified to species or genus level using macro and micro-histological techniques. Both species consumed a wide variety of food items but M. lagotis exhibited a greater use of invertebrate material and B. lesueur consumed more roots and perennial vegetation. Both species consumed a variety of seeds. There was high seasonal variation in the diets of both species and they appeared to be opportunistic dietary generalists, a condition beneficial for survival in the unpredictable arid zone climate. Although both species consumed items from the same broad dietary categories there was little dietary overlap of specific food items. Where overlap existed it was either temporally separated or comprised less than 19% of the total dietary volume suggesting a degree of resource partitioning between the two species. Whilst M. lagotis appears to have adapted to arid conditions by moving to follow ephemeral growth, B. lesueur is more sedentary and relies more on perennial vegetation. Within re-introduced confined populations where species movement is limited, M. lagotis may be more susceptible to population decline when conditions are dry, whereas B. lesueur may cause significant damage to perennial vegetation before experiencing population decline.

A trial re‐introduction of the Greater Stick‐nest Rat (Leporillus conditor) in arid South Australia

Summary Eight Greater Stick‐nest Rats (Leporillus conditor S.) were re‐introduced into a 8 ha release pen within the Arid Recovery Reserve, South Australia, in September 1998. Their weight, reproductive condition, activity, habitat use and grazing impacts were investigated during the 8 month experimental trial. Greater Stick‐nest Rats increased in weight and bred successfully after the end of summer (April 1999). They consumed native vegetation including Bladder Saltbush (Atriplex vesicaria), Ruby Saltbush (Enchylaena tomentosa) and Sturt's Pigface (Gunniopsis quadrifida) but Sturt's Pigface was most heavily browsed and no monitored plants died from over‐browsing during the trial. Rats preferred dune habitat and the two largest female rats maintained discrete activity areas and shelter sites. Nocturnal activity of adult male rats was centred around adult females with both sexes generally staying within 150 m of daytime shelter sites. Shelter sites were commonly within dead Umbrella Wattle (Acacia ligulata) or Narrow‐leafed Hopbush (Dodonaea viscosa) shrubs covered in low vegetation, and rats also adapted burrows of other species to use as below‐ground components. Although supplementary water was provided and may have ensured survival over the hot summer months, the trial release was considered a success and a full‐scale re‐introduction of the Greater Stick‐nest Rat was conducted in 1999.