Loggerhead turtle (Caretta caretta) nest predation at Cape Range National Park

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 have declined by 86% since the 1970s. However, whilst Eastern Australian loggerhead populations have been extensively studied and monitored, not much is known about the Western Australian nesting population

Wildlife disease passive surveillance: Are wildlife rehabilitation centres a tool? A case study.

Wildlife rehabilitation centre records are an often unexploited source of crucial information on species morbidity and mortality. Analysis of these records can be used to assess and improve rehabilitation techniques

Factors affecting hatching and emergence success at two important Loggerhead Turtle (Caretta caretta) nesting beaches in Western Australia

The loggerhead turtle (Caretta caretta) nesting population in Western Australia is estimated to consist of about 1,500 females, and is consequently the largest nesting population in Australia. However, while the Eastern Australian stock has been extensively studied and monitored since 1968, no long-term data is available for any Western Australian index beach. Dirk Hartog Island, within the Shark Bay World Heritage Area (Gascoyne region), is by far the largest loggerhead turtle nesting ground in Australia and current data suggests that loggerhead turtles nesting at Dirk Hartog Island represent 70-75% of nesting loggerheads found in the whole Eastern Indian Ocean. This study aims to assess several biotic and abiotic factors affecting hatching and emergence success in two loggerhead turtle nesting beaches in Western Australia: Turtle Bay on Dirk Hartog Island and the smaller mainland nesting beach located at the Bungelup section of Cape Range National Park (North West Cape Peninsula, Pilbara region)

Health assessment of Loggerhead Turtles (Caretta caretta): nesting fermales and hatchlings

Most of the existing sea turtle populations world wide are in decline. This has been largely attributed to anthropogenic factors such as coastal development; poaching, fisheries by-catch, climate change and pollution. Loggerhead turtles (Caretta caretta) are listed as endangered (IUCN, 2006). The loggerhead nesting population in Western Australia is estimated to consist of about 1500 females, and is consequently the largest nesting population in Australia and one of the largest in the Indian Ocean (Baldwin et al. 2003)

Key parameters describing temperature-dependent sex determination in the southernmost population of loggerhead sea turtles

All marine turtles have temperature-dependent sex determination (TSD), and there is mounting evidence that climate change has increased sand temperatures at some rookeries, leading to pronounced biases in hatchling sex ratios. Quantification of the variation in the key parameters that describe TSD will be essential to our ability to predict the adaptive capacity of marine turtles, and for implementing conservation programs where necessary. Here we integrate field and laboratory data on the embryonic development of a little-studied population of loggerhead turtles ( Caretta caretta, Linnaeus 1758) from Western Australia, which is home to a large rookery at the southernmost limit of the species' global range. We determined that the pivotal temperature that produces an equal sex ratio was 29.0. °C, centred within a transitional range of temperatures of 0.67. °C where both sexes are produced. For the first time for a marine turtle, embryonic development rates were modelled with a non-linear function, and were used to define the start and end of the thermosensitive period, where bipotential gonads differentiate into testes or ovaries. The period where gonads were sensitive to a masculinizing trigger occurred between 33 and 64% of development. In general, the TSD parameters for this southernmost population of C. caretta were similar to those estimated for other loggerhead populations, reinforcing previous findings that sex determination thresholds and processes are highly conserved

Health and hatching success of Western Australian loggerhead turtle (Caretta caretta) nesting populations

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

Augmenting the conservation value of rehabilitated wildlife by integrating genetics and population modeling in the post-rehabilitation decision process

Insular populations are particularly vulnerable to the effects of stochastic events, epidemics, and loss of genetic diversity due to inbreeding and genetic drift. The development of successful management options will require accurate baseline data, establishment of clear objectives, and finally monitoring and implementation of corrective measures, if and when required. This study assessed management options for the genetic rehabilitation of highly inbred woylies obtained from wildlife rehabilitation centers. The study generated genetic data for the woylie Bettongia penicillata from a conservation reserve and calculated measures of genetic diversity and individual relatedness. These data were fed into a population viability analysis (PVA) to test genetic outcomes in relation to different management actions. We demonstrated that a careful selection of the founder cohort produced a population with an expected heterozygosity of ∼70% for a window of approximately 10 years. A proposal to increase the size of the reserve available to the colony was shown to almost double the time at which the colony would retain heterozygosity levels of ≥ 70%. Additionally, developing a regular program of supplementation of unrelated woylies would result in a further improvement in their genetic value. This study demonstrated how the application of molecular techniques in combination with PVA can be beneficial for the management of rehabilitated wildlife otherwise considered of little conservation value. This approach can be applied to the management of breeding programs, but also to small, closed populations such as those found on islands, fenced enclosures, insurance populations, and in zoological collections

Integrating population genetics in an adaptive management framework to inform management strategies

Adequate levels of genetic diversity are important for long term persistence of wildlife species, yet genetic principles have only been considered in the last few years when developing management plans for conservation purposes. We present here an example on how genetic management plans can be explicitly integrated into an adaptive management framework. This can be achieved by developing a predictive model to explore population responses to different management options, and by quantifying management targets that should be verified through monitoring programs. We apply this approach to the woylie or brush tailed bettong (Bettongia penicillata); an Australian macropod, listed as Critically Endangered. Results suggest that discrete small populations (e.g.  30 woylies/year over the course of several years is recommended. Formal completion of the adaptive management approach would include, in addition to the stages presented here, a quantitative assessment of the outcome of management and continue refinement of the modelling framework on the basis of new data gained through ongoing monitoring. We encourage the formal inclusion of genetic management within the adaptive management framework as demonstrated in this study

Is supplementation an efficient management action to increase genetic diversity in translocated populations?

It is generally assumed that population supplementation will improve the genetic diversity of the recipient populations. However, the genetic outcomes of supplementations are rarely tested. We used population modelling to predict how the supplementation programme in a translocated Woylie (Bettongia penicillata ogilbyi) population influences their genetic makeup. Our model projections were then compared against real genetic data collected before and after supplementation, to determine whether or not supplementation was effective at increasing genetic diversity and to test the accuracy of the model. Post‐supplementation genetic diversity parameters (heterozygosity and allelic richness) were significantly higher following supplementation, and there was no significant difference from those predicted by the model. These results are encouraging; however, many factors can influence supplementation outcomes and we recommend ongoing monitoring in translocated populations to ensure that population trends are on target