Dorian Moro

MURINE VIRUSES IN AN ISLAND POPULATION OF INTRODUCED HOUSE MICE AND ENDEMIC SHORT-TAILED MICE IN WESTERN AUSTRALIA

House mice (Mus domesticus) were recently introduced to Thevenard Island, off the northwest coast of Western Australia. This island is also habitat for an endangered native rodent, the short-tailed mouse (Leggadina lakedownensis). Concerns have been raised that house mice may pose a threat to L. lakedownensis both through competition and as a source of infection. To assess the threat to L. lakedownensis posed by viral pathogens from M. domesticus, a serological survey was conducted from 1994 to 1996 of both species for evidence of infection with 14 common murine viruses (mouse hepatitis virus, murine cytomegalovirus, lymphocytic choriomeningitis virus, ectromelia virus, mouse adenovirus strains FL and K87, minute virus of mice, mouse parvovirus, reovirus type 3, Sendai virus, Theilers mouse encephalomyelitis virus, polyoma virus, pneumonia virus of mice, and encephalomyocarditis virus) and Mycoplasma pulmonis. Despite previous evidence that populations of free-living M. domesticus from various locations on the Australian mainland were infected with up to eight viruses, M. domesticus on Thevenard Island were seropositive only to murine cytomegalovirus (MCMV). Antibodies to MCMV were detected in this species at all times of sampling, although seroprevalence varied. Infectious MCMV could be isolated in culture of salivary gland homogenates from seropositive mice. In contrast, L. lakedownensis on Thevenard Island showed no serological evidence of infection with MCMV, any of the other murine viruses, or M. pulmonis, and no virus could be isolated in culture from salivary gland homogenates. Although MCMV replicated to high titers in experimentally infected inbred BALB/c laboratory mice as expected, it did not replicate in the target organs of experimentally inoculated L. lakedownensis, indicating that the strict host specificity of MCMV may prevent its infection of L. lakedownensis. These results suggest that native mice on Thevenard Island are not at risk of MCMV infection from introduced house mice, and raise interesting questions about the possible selective survival of MCMV in small isolated populations of M. domesticus.

Conservation significance of island versus mainland populations: a case study of dibblers (Parantechinus apicalis) in Western Australia

Island populations are an interesting dichotomy in conservation biology. On the one hand, they can be a refuge for species where mainland populations have been decimated by loss of habitat and predation by exotic predators. On the other hand, island populations usually have reduced genetic diversity and are more susceptible to extinction through genetic and demographic processes. Genetic variation and morphological characters were measured for island and mainland populations of Parantechinus apicalis, small dasyurid marsupials, restricted to southwest Australia. Genetic variation at seven microsatellite loci revealed low levels of heterozygosity (He = 0.20 - 0.44) and high levels of inbreeding (Fe = 0.40 - 0.72) in island populations compared with the mainland population (He = 0.73). A nested clade analysis revealed that allopatric fragmentation was probably responsible for the association between geographical location and control region haplotypes, which is consistent with the isolation of populations on islands and indicative of two main populations of P. apicalis representing separate conservation units for management. While these results are typical of many island populations, they have important implications in terms of the conservation of threatened species in Australia and around the world, where island populations are a common source of founders for captive breeding and translocation to mainland sites.

Translocation of captive-bred dibblers Parantechinus apicalis (Marsupialia: Dasyuridae) to Escape Island, Western Australia

Abstract The introduction of threatened marsupials to islands affords a high degree of translocation success due to the lack of exotic species on islands, or the feasibility of eradicating them. The dibbler Parantechinus apicalis is a small marsupial endemic to the southwest of Australia. It is listed under international and national legislation as Endangered, and has been the focus of a successful conservation strategy to introduce captive-bred individuals to an island as a security measure, and as part of a formal Interim Recovery Plan. A total of 88 individuals were released in four groups on Escape Island from 1998 to 2000. The population was monitored using radiotelemetry and trapping techniques from 1998 to 2001. Breeding and dispersal of young occurred within the first year of release. Three years after the initial release, the third generation of wild-born dibblers had entered into the population. The total cost of this translocation exercise approximated

Movements and refugia of Lakeland Downs short-tailed mice, Leggadina lakedownensis, and house mice, Mus domesticus, on Thevenard Island, Western Australia

AUS 0.6 million. The conservation effort to give additional security to dibblers has been successful, at least in the short term, due to the collaboration between four organisations and a commitment to support a monitoring program of the released population over time.

Evaluation and cost-benefits of controlling house mice (Mus domesticus) on islands: an example from Thevenard Island, Western Australia

Radio-telemetry was used to identify the home range and refuge sites of two species of mouse inhabiting a semi-arid island off the Western Australian coast, in an effort to understand differences in their water metabolism. The native short-tailed mouse, Leggadina lakedownensis, had a median home range of 4.8 ha. This area increased during the non-breeding season (5.3 ha) compared with the breeding season (3.0 ha), but this difference was not significant. In contrast, the median home range for the house mouse, Mus domesticus, was smaller (2.8 ha), although this was variable. Core areas were best represented by the 75% and 60% isopleths for M. domesticus and L. lakedownensis, respectively. Core areas were greater in L. lakedownensis (1.0 ha) than in M. domesticus (0.8 ha). Furthermore, the degree of overlap in core areas was low for L. lakedownensis, but absent for M. domesticus. There was no evidence that M. domesticus used burrows as refuges. Instead, they sheltered in dense bushes above ground during the day where air temperatures were ameliorated by the cover. L. lakedownensis rested in burrows during the day where high air temperatures were mainatined at a constant 28°C, and a relative humidity of between 72–97%. Burrow morphology was simple and comprised two types: burrows with a single chamber, and those without a chamber, indicative of a solitary habit. These results suggest that a fossorial behaviour in L. lakedownensis may lower its water economy compared with M. domesticus, which shelters above ground.

Importance of diurnal refugia to a hare-wallaby reintroduction in Western Australia

Abstract Feral mammals occur on many offshore islands around Australia, but their eradication by poison-baiting requires a careful assessment of the associated costs and long-term benefits. This paper describes a replicated trial program to poison house mice Mus domesticus selectively on Thevenard Island, Western Australia, in the presence of a native species of mouse, and to evaluate whether the eradication of house mice from the island is an achievable and cost-effective goal. It was found the densities and survivorship of house mice declined more on grids with bait stations spaced every 10 m than on grids baited every 20 m when compared to unbaited (control) grids. On one grid baited every 10 m, the abundance of house mice declined by 83% 22 days after baiting commenced. This decline was correlated with an increase in the abundance of short-tailed mice Leggadina lakedownensis on the grid. A total of 55 person days was required to conduct the present poison-baiting trials, and expenses incurred were over

Food availability for the dibbler (Parantechinus apicalis) on Boullanger and Whitlock Islands, Western Australia

AUS1000 ha−1. Baiting islands for house mice can prove a costly excercise, and management organisations need to assess whether ground-based baiting is an efficacious and cost-effective management option if complete eradication fails.

Bait Uptake and Caching by Red Foxes and Nontarget Species in Urban Reserves

In an effort to learn more about the potential for reintroduction of hare-wallabies to sites in Australia, 34 captive-bred hare-wallabies were released onto Peron Peninsula within the Shark Bay World Heritage Property in 2001 as part of an experimental reintroduction program. One objective of this experiment was to characterise their behaviour and daytime refugia to identify suitable habitat for future releases. The mala (Lagorchestes hirsutus) and merrnine (Lagostrophus fasciatus) were fitted with radio-transmitters and tracked daily. Merrnine were more faithful to a previously occupied shelter than mala. Mala maintained a solitary daytime habit at all times. Within the study area, mala preferentially sought low-lying vegetation primarily comprising the species Lamarchea hakeifolia, which provided dense cover up to 1 m in height, under which they constructed scrapes. L. hakeifolia was preferred as shelter vegetation instead of Triodia (spinifex) hummocks, despite Triodia hummock habitat being preferred by mala in central Australia. Merrnine occupied taller vegetation with an open understorey to 1.5 m, although the extremity of the understorey remained dense at this height. Individual merrnine sometimes sheltered with conspecifics of the opposite sex. Since both species utilised floristically and structurally variable vegetation, we suggest that they have the ability to cope with vegetation that has been altered by changes in fire regimes and introduced herbivores. This is particularly important for future reintroduction exercises as the results suggest that vegetation characteristics required to support these species, particularly mala, may be variable rather than limited to perceived necessary habitat types in central Australia or on islands. These results should allow future reintroduction projects to consider a wider range of release-site options during their planning phase.

Population structure and dynamics of sympatric house mice, Mus domesticus, and Lakeland Downs short-tailed mice, Leggadina lakedownensis, on Thevenard Island, Western Australia

The aim of this study was to assess food availability for the dibbler (Parantechinus apicalis) on Boullanger and Whitlock Islands in different habitats and seasons. This was assessed by capturing ground-dwelling invertebrates in pitfall traps in winter, spring and autumn. A quantitative faecal-pellet analysis was conducted to determine the composition of the diet. There were no significant differences in the number of invertebrates captured in the different seasons, or in the different habitat types on the islands. The proportion of plant versus animal matter in the faecal pellets did not change significantly between the seasons. The diet consisted of ~20% plant material. The scat analysis showed that dibblers consumed at least 10 orders of invertebrates ranging in length from 0.1 mm to 25 mm with an average size of 4.5 ± 0.4 mm. The dibblers did not select for a particular size or taxon of prey, but fed on any invertebrates that were readily available to them. This suggests that dibblers are essentially insectivorous dietary generalists and opportunists. The information gathered in this study could be applied when considering available food resources at future translocation sites for dibblers.

Optimising reintroduction success by delayed dispersal: Is the release protocol important for hare-wallabies

Abstract The management of biodiversity in urban areas provides a challenge for conservation managers who are interested in the recovery of native species by controlling exotic species. Exotic-animal control programs using poisons can be contentious in terms of the health and safety of nontarget species, including people. Managing exotic predators in urban areas must be effective at 2 levels: controlling the target species and minimizing impacts to nontarget species. We investigated the feasibility of instigating a poison-baiting program to control nonindigenous European red foxes (Vulpes vulpes) in city conservation reserves (Perth, Australia). We selected 3 reserves to assess the safety and efficacy of baiting for foxes by maximizing bait uptake by the target species, and minimizing uptake by nontarget species. We tested 2 types of meat bait using 4 bait presentation methods (untethered, uncovered; untethered, covered; tethered, uncovered; tethered, covered). Bait uptake by foxes was highest in urban reserves compared to that in a peri-urban reserve. Bait type and presentation method equally explained bait uptake by foxes. Untethered and uncovered baits were removed 10% more often by foxes, and untethered baits had been cached more often than tethered baits. Baits cached by foxes for up to 1 week were not removed by species other than foxes. Domestic dogs and native birds were common nontarget species to remove baits. Dogs showed no aversion to removing any bait type, nor did bait presentation method influence bait removal. Birds removed fewer baits that had been tethered and covered. We provide an evidence base to demonstrate that bait uptake by nontarget species can be minimized, although we suggest that a fox control program is likely to be more of an organizational challenge to change public attitudes toward responsible dog ownership rather than a technical challenge to poison foxes.