Hunting pressure is a key contributor to the impending extinction of Bornean wild cattle

Widespread and unregulated hunting of ungulates in Southeast Asia is resulting in population declines and localised extinctions. Increased access to previously remote tropical forest following logging and changes in land-use facilitates hunting of elusive wild cattle in Borneo, which preferentially select secluded habitat. We collated the first population parameters for the Endangered Bornean banteng Bos javanicus lowi and developed population models to simulate the effect of different hunting offtake rates on survival and the recovery of the population using reintroduced captive-bred individuals. Our findings suggest that the banteng population in Sabah is geographically divided into 4 management units based on connectivity: the Northeast, Sipitang (West), Central and Southeast, which all require active management to prevent further population decline and local extinction. With only 1% offtake, population growth ceased in the Northeast and Sipitang. In the Southeast and Central units, growth ceased at 2 and 4% offtake, respectively. Extinction was estimated at 21-39 yr when offtake was 5%, occurring first in Sipitang and last in the Central unit. Supplementing the population with captive-bred individuals suggested that inbreeding was likely to limit population growth if using ≤20 founder individuals. Translocating 2 individuals for a 10 yr period, starting after 20 yr of captive breeding resulted in a faster population recovery over 100 yr and a lower extinction probability. Our results suggest that shielding the population against further losses from hunting will be key to their survival in the wild, provided that active management in the form of captive breeding is developed in the interim.

Assessment of the status and trends in abundance of a coastal pinniped, the Australian sea lion Neophoca cinerea

Australian sea lions Neophoca cinerea are endemic to Australia, with their contemporary distribution restricted to South Australia (SA) and Western Australia (WA). Monitoring of the species has proved challenging due to prolonged breeding events that occur non-annually and asynchronously across their range. The most recent available data from 80 extant breeding sites (48 in SA, 32 in WA) enabled us to estimate the species-wide pup abundance to be 2739, with 82% (2246) in SA and 18% (493) in WA, mostly based on surveys conducted between 2014 and 2019. We evaluated 1776 individual site-surveys undertaken between 1970 and 2019 and identified admissible time-series data from 30 breeding sites, which revealed that pup abundance declined on average by 2.0% yr-1 (range 9.9% decline to 1.7% growth yr-1). The overall reduction in pup abundance over 3 generations (42.3 yr) was estimated to be 64%, with over 98% of Monte Carlo simulations producing a decline >50% over a 3-generation period, providing strong evidence that the species meets IUCN ‘Endangered’ criteria (decline ≥50% and ≤80%). The population is much smaller than previously estimated and is declining. There is a strong cline in regional abundances (increasing from west to east), with marked within-region heterogeneity in breeding site pup abundances and trends. Results from this study should improve consistency in the assessment of the species and create greater certainty among stakeholders about its conservation status. To facilitate species management and recovery, we prioritise key data gaps and identify factors to improve population monitoring.

Feminization of hawksbill turtle hatchlings in the twenty-first century at an important regional nesting aggregation

Projected climate change is forecasted to have significant effects on biological systems worldwide. Marine turtles in particular may be vulnerable, as the sex of their offspring is determined by their incubating temperature, termed temperature-dependent sex determination. This study aimed to estimate historical, and forecast future, primary sex ratios of hawksbill turtle Eretmochelys imbricata hatchlings at an important nesting ground in northeastern Qatar. Incubation temperatures from the Arabian/Persian Gulf were measured over 2 nesting seasons. Climate data from same period were regressed with nest temperatures to estimate incubation temperatures and hatchling sex ratios for the site from 1993 to 2100. Future hatchling sex ratios were estimated for 2 climate forecasts, one mid-range (SSP245) and one extreme (SSP585). Historical climate data showed female-biased sex ratios of 73.2 ± 12.1% from 1993 to 2017. Female biases from 2018 to 2100 averaged 85.7% ± 6.7% under the mid-range scenario and 87.9% ± 5.4% under the high-range scenario. In addition, predicted female hatchling production was >90% from 2054 and 2052 for SSP245 and SSP585, respectively. These results show that hawksbill primary sex ratios in Qatar are at risk of significant feminization by the year 2100 and that hawksbill turtle incubation temperatures in an extreme, understudied environment are already comparable to those predicted in tropical rookeries during the latter half of the 21st century. These results can help conservationists predict primary sex ratios for hawksbill turtles in the region in the face of 21st-century climate change.