Ecology and Conservation of a New Carnivorous Marsupial Species: the Silver-Headed Antechinus (Antechinus argentus)

Abstract

The genus Antechinus comprises 15 species of small carnivorous marsupials endemic to Australia. Five of these have been described since 2012 on the basis of combined genetic, morphological and ecological data. One new species, the threatened silver-headed antechinus (Antechinus argentus) was described in 2013. When the present study commenced the species had only been found at one location: the south-eastern plateau of Kroombit Tops National Park, south-west of Gladstone in mid-east Queensland, Australia -an area encompassing less than 10 km 2 . However, the study that described the species was based on data obtained from only 15 individuals used for taxonomic description; thus, little was known about the biology of A.argentus. Therefore, the major component of the present study investigated three broad areas of the species' ecology for which knowledge was sparse or non-existent, with the aim of providing foundational ecological knowledge to prioritise conservation management: 1. dietary strategy and composition; 2.life-history traits; 3. post-fire habitat use. Additional work was carried out to examine the potential influence of rainfall patterns on population dynamics of A. argentus, and widespread trapping surveys were undertaken with the aim of establishing a cogent distributional range of the species, which resulted in the discovery of a second population ~200 km distant from the type locality.During 2014, faecal pellets were collected each month (March-September) from a population at the type locality to gather baseline data on diet composition. A total of 38 faecal pellets were collected from 12 individuals (eight females, four males) and microscopic analysis of pellets identified seven invertebrate orders, with 70% combined mean composition of beetles (Coleoptera: 38%) and cockroaches (Blattodea: 32%). Other orders that featured as prey were ants, crickets/grasshoppers, butterflies/moths, spiders, and true bugs. Given that faecal pellets could only be collected from a single habitat type (Eucalyptus montivaga high-altitude open forest) and location, this was best described as a generalist insectivorous diet that is characteristic of other previously studied congeners.iv Antechinuses are well-known for their spectacular annual male die-off at the close of a one-to three-week mating period. The genus also displays sexual dimorphism for size-males are up to three times heavier than females. The A.argentus population studied at Kroombit Tops National Park over two years followed the trends of the genus, with strong evidence of both a synchronised male die-off (in June/July) and significantly larger males than females. Two proximate sites where A. argentus was previously known to occur were surveyed. Unexpectedly, there was a marked difference in A. argentus numbers between years and sites. It was hypothesised that the disparate capture rates between sites may be at least in part linked to the effects of fire on vegetation.Management of critical habitat for threatened species with small ranges requ...