Harriet R. Mills

Conservation translocations have become increasingly popular for ‘rewilding’ areas that have lost their native fauna. These multispecies translocations are complex and need to consider the requirements of each individual species as well as the influence of likely interactions among them. The Dirk Hartog Island National Park Ecological Restoration Project, Return to 1616, aspires to restore ecological function to Western Australia’s largest island. Since 2012, pest animals have been eradicated, and conservation translocations of seven fauna species have been undertaken, with a further six planned. Here, we present a synthesis of the innovative approaches undertaken in restoring the former faunal assemblage of Dirk Hartog Island and the key learnings gathered as the project has progressed.

The loss of genetic variation and genetic divergence from source populations are common problems for reintroductions that use captive animals or a small number of founders to establish a new population. This study evaluated the genetic changes occurring in a captive and a reintroduced population of the dibbler (Parantechinus apicalis) that were established from multiple source populations over a twelve-year period, using 21 microsatellite loci. While the levels of genetic variation within the captive and reintroduced populations were relatively stable, and did not differ significantly from the source populations, their effective population size reduced 10–16-fold over the duration of this study. Evidence of some loss of genetic variation in the reintroduced population coincided with genetic bottlenecks that occurred after the population had become established. Detectable changes in the genetic composition of both captive and reintroduced populations were associated with the origins of the individuals introduced to the population. We show that interbreeding between individuals from different source populations lowered the genetic relatedness among the offspring, but this was short-lived. Our study highlights the importance of sourcing founders from multiple locations in conservation breeding programs to avoid inbreeding and maximize allelic diversity. The manipulation of genetic composition in a captive or reintroduced population is possible with careful management of the origins and timings of founder releases.

Aim: Identifying the variables that influence animal home range size is important for understanding the biological requirements of individuals and their social interactions. Given their often broad distributions, carnivores are model organisms for studying range‐wide determinants of home range size. Here, we test predictions about environmental determinants of home range size for one of the world's most widely distributed carnivores, the red fox (Vulpes vulpes).Location: Global.Methods: We compiled a database of 70 mean home range estimates from 62 studies and four continents, which we analysed according to site‐based temperature, precipitation, environmental productivity and human influence variables.Results: We found a very strong negative effect of the Human Footprint Index (HFI), with fox home range size decreasing as the level of human impact increased. When analysing the constituent components of the HFI separately, we found that human population density was the only well‐supported variable (cf. built environments, croplands, pasture lands, nightlights, railways, roads and navigable waterways). Predicted home range size at the highest human population densities (0.75 km²) was 93% lower than at the lowest population densities (10.83 km²). We also found that home range size increased as mean annual temperature and temperature seasonality increased. The analyses did not support our prediction that home ranges would be smaller in areas of higher environmental productivity or precipitation.Main conclusions: Smaller home range sizes observed in highly disturbed areas can be attributed to increased food availability from anthropogenic sources. The lack of an effect of environmental productivity contrasts with previous studies that have shown a negative relationship with carnivore home range size. It may be that anthropogenic food sources have negated the impacts that low‐productivity environments have on fox home ranges. Our results emphasize the strong potential for human activities to transform animal space use across the globe.

The use of multiple source populations provides a way to maximise genetic variation and reduce the impacts of inbreeding depression in newly established translocated populations. However, there is a risk that individuals from different source populations will not interbreed, leading to population structure and smaller effective population sizes than expected. Here, we investigate the genetic consequences of mixing two isolated, morphologically distinct island populations of boodies (Bettongia lesueur) in a translocation to mainland Australia over three generations. Using 18 microsatellite loci and the mitochondrial D-loop region, we monitored the released animals and their offspring between 2010 and 2013. Despite high levels of divergence between the two source populations (F_ST = 0.42 and ϕ_ST = 0.72), there was clear evidence of interbreeding between animals from different populations. However, interbreeding was non-random, with a significant bias towards crosses between the genetically smaller-sized Barrow Island males and the larger-sized Dorre Island females. This pattern of introgression was opposite to the expectation that male–male competition or female mate choice would favour larger males. This study shows how mixing diverged populations can bolster genetic variation in newly established mammal populations, but the ultimate outcome can be difficult to predict, highlighting the need for continued genetic monitoring to assess the long-term impacts of admixture.

A fifth of all species in the carnivorous‐insectivorous marsupial family Dasyuridae show obligate male semelparity (die‐off), where males die after their first mating season, but females may breed in more than one season. Life history strategies of many species in the genera Antechinus and Phascogale are well known, but the other dasyurid genus with apparently obligately semelparous males, Dasykaluta, is poorly known, and there have been no demographic studies of this monotypic genus in the wild. Both sexes in Antechinus and Phascogale species are highly polygamous. Comparative and experimental tests of insectivorous marsupials indicate that this polygamy is linked to the evolution of semelparity in more strongly seasonal breeders, through intense sperm competition. We assessed whether the kaluta (Dasykaluta rosamondae), a small dasyurid endemic to the broader Pilbara region of Western Australia, has obligate male semelparity, multiple paternity within litters, and positive testis allometry in the wild. We documented complete die‐off of males over two breeding seasons. Multiple paternity was confirmed in seven of eight litters, where either two or three fathers sired young. The seven young in the remaining litter appeared to be sired by one male. Intraspecific positive testis allometry was found in adult males. We conclude that the life history strategies of wild male and female kalutas are consistent with those of the two other genera of dasyurids with obligate male semelparity (Antechinus and Phascogale), and sperm competition is likely to be important in the mating system of kalutas. Our results show that male obligate semelparity has evolved twice in dasyurids.

Understanding patterns in the distribution and abundance of wildlife across the landscape can aid in identifying the relative importance of habitats for biodiversity conservation. We aimed to identify whether riparian habitats were more important than other areas in the landscape to small terrestrial vertebrates. The study site was surveyed using 450 pit traps distributed across riparian, midslope and ridge top habitat. Riparian sites had the greatest abundance of small vertebrates of the three habitats. During some months of the year, there was a significant difference in the composition of the faunal assemblage between habitats. Unsurprisingly, riparian habitats were particularly important for frog species and it was these species that accounted for the greater abundance in this habitat. Riparian habitat was less important for other taxonomic groups and the more floristically rich midslope and ridge habitats, which had a greater abundance of leaf litter, fallen logs and rock cover, were favoured by mammal and reptile species. The conservation of riparian sites, without the protection of other habitats, overlooks a substantial proportion of the biodiversity in the landscape. This study may help inform management decisions in the Upper Warren region and other similar forested landscapes, regarding the location and timing of fauna monitoring and the frequency of fuel reduction burns.

The aim of this study was to investigate how landscape disturbance associated with roads, agriculture and forestry influenced temporal patterns in woylie (Bettongia penicillata) abundance before, during and after periods of rapid population change. Data were collected from an area of approximately 140,000 ha of forest within the Upper Warren region in south-western Australia. Woylie abundance was measured using cage trapping at 22 grid and five transect locations with varying degrees of landscape disturbance between 1994 and 2012. We found evidence that the distribution and abundance of woylies over time appears to be related to the degree of fragmentation by roads and proximity to agriculture. Sites furthest from agriculture supported a greater abundance of woylies and had slower rates of population decline. Sites with fewer roads had a greater abundance of woylies generally and a greater rate of increase in abundance after the implementation of invasive predator control. The results of this study suggest that landscape disturbance is less important at peak population densities, but during times of environmental and population change, sites less dissected by roads and agriculture better support woylie populations. This may be due to the role these factors play in increasing the vulnerability of woylies to introduced predators, population fragmentation, weed species invasion, mortality from road collisions or a reduction in available habitat. Strategies that reduce the impact of disturbance on woylie populations could include the rationalisation of forest tracks and consolidation of contiguous habitat through the acquisition of private property. Reducing the impact of disturbance in the Upper Warren region could improve the resilience of this critically important woylie population during future environmental change.