Kristin Warren

There is compelling evidence of broad-scale declines in populations of small terrestrial native mammals in northern Australia, including the Top End of the Northern Territory (NT) over the past 20 years. Causes under consideration include changed fire regimes, introduced fauna (including predators) and disease. To date information on health and disease in northern Australian mammals has been limited. Disease is increasingly recognised as a primary driver of some wildlife population declines and extinctions e.g., Tasmanian devil facial tumour disease, white nose syndrome in bats and chytrid fungus in amphibians. Disease has been identified as a risk factor for extinction in declining and fragmented wildlife populations globally, particularly in situations of increased environmental stressors, changing ecosystems, arrival of new vertebrate threats or climate change. Unless wild populations are studied in detail over long periods of time, the effects of disease are easily overlooked and may be difficult to determine. This study is the largest and most comprehensive study of health and disease in small mammals in northern Australia and is one of a small number of studies worldwide to have approached investigation of wildlife populations in this comprehensive manner.

Most of the existing sea turtle populations worldwide are in decline. In particular, loggerhead turtles (Caretta caretta) are listed as endangered and loggerhead nesting populations in Eastern Australia declined by 86% since the 1970s. This study aims to collect critical baseline data regarding health and hatching success of the loggerhead turtle nesting population in Cape Range National Park. Adult nesting turtles were examined and a blood sample taken to establish reference ranges of several blood health parameters and screen for toxin levels. The marked nests were excavated after observed hatchling emergence to establish hatching and emergence success, and collect samples of dead hatchlings and embryos for further histological examination, as well as unhatched eggs for toxin screening. Additionally, all nests were monitored for signs of predation. The research was conducted for two nesting seasons (2006/07 and 2007/08) and initial results show that in Cape Range National Park nest predation is a crucial limiting factor affecting hatching success. Predation by ghost crabs (Ocypode spp), monitor lizards (Varanus giganteus) and feral European red foxes (Vulpes vulpes), considerably reduce survivorship from egg to hatchling. In fact, in the first and second years of this study 78.2% and 83.3% of the monitored nests respectively, showed signs of partial or complete nest predation. It is unlikely that this mainland nesting population can sustain such severe level of predation pressure, especially in conjunction with other anthropogenic causes of decline at foraging sites and during migration to the nesting site (i.e. poaching, fisheries by-catch and pollution), and more studies are recommended to identify successful management strategies to reduce nest predation on this beach. This study takes an important first step towards obtaining crucial information on loggerhead turtle nest ecology and nesting turtle health in this region.