The post-mating mortality of males in dasyurid species is thought to be a specific life-history strategy, associated with a tightly synchronised breeding season, that may enhance survivorship of juveniles. Parantechinus apicalis has been reported to exhibit male die-off in island populations but not in mainland populations, and males originating from both island and mainland populations are known to survive post-mating in captivity. However, males in the island populations have been reported to sometimes survive to breed in a second year. This study monitored captive and island populations over a three-year period (April 1997 – May 2000) to examine the extent of male die-off. In captivity, males showed no evidence of post-mating mortality. Males on one island were also found to survive post-mating, while another island population appeared to have high mortality of males in three years, and a complete male die-off after the 1999 breeding season. We conclude that P. apicalis may warrant inclusion in a new category of life-history strategy for species exhibiting facultative male die-off.

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.

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 (H_e= 0.20−0.44) and high levels of inbreeding (F_e= 0.40−0.72) in island populations compared with the mainland population (H_e= 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.

Despite decades of interest, adaptive explanations for biased offspring sex ratios in mammals remain contentious, largely because direct tests of the underlying fitness assumptions of adaptive hypotheses are rarely conducted. These tests are complicated by the difficulty of manipulating offspring sex prior to significant maternal investment owing to the biological constraints of viviparity. We test the adaptive advantage of sex allocation through cross-fostering offspring by sex in tammar wallabies. We examine whether offspring sex is correlated with maternal investment ability (i.e. Trivers–Willard hypothesis, TWH). In addition, we test the assumption that maternal investment has a greater influence on the fitness of sons than of daughters. We failed to find statistical support for maternal investment ability influencing a son's weaning success or body size more than a daughter's, although this result was probably owing to small sample sizes. In support of the TWH, females that gave birth to a son had higher investment ability (likelihood of weaning an offspring) regardless of the sex of offspring fostered.

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.