Amphibians have suffered widespread declines caused by many interacting factors whose effects are often difficult to isolate. We used complementary analyses to decouple effects of methylmercury (MeHg) and amphibian chytrid fungus (Bd) on survival of Columbia Spotted Frogs (Rana luteiventris) during a 5-year capture-mark-recapture study. We also evaluated whether effects on apparent survival were mediated through physiological responses (corticosterone, CORT). While Bd was unrelated to frog survival, geometric mean MeHg bioaccumulation in our population (164 ng/g) reduced survival by ~20%. Baseline CORT was negatively associated, and stress-induced CORT was positively associated with higher MeHg, suggesting that MeHg dysregulated glucocorticoid physiology. Survival was positively associated with higher baseline CORT, whereas survival was negatively associated with higher stress-induced CORT. Our results provide rare evidence linking CORT and long-term survival of wild vertebrates and that environmentally relevant concentrations of MeHg can influence survival of free-ranging amphibians, and these effects may be mediated by CORT.
Monitoring of the critically endangered Far Eastern leopard is crucial for understanding population status and trends to assess the effectiveness of conservation interventions. This study provides an up-to-date assessment of the Far Eastern leopard population in the southwest of Primorsky Krai, Russia. Population parameters were derived from camera trap monitoring data conducted in the protected areas in 2022. The analysis of population size and density was carried out using the spatially explicit capture-recapture method. A total of 116 individuals were identified: 104 adults and 12 cubs. The estimated population size was 118 individuals (95% CI: 115–121), with a population density of 2.46 individuals/100 km2, which is 20% higher than previously published estimations for 2020 and doubled since 2014. A reassessment of the global population of Far Eastern leopards will require a combination of data from both Russia and China, as was done in 2014 and 2015.
Swamp rabbits (Sylvilagus aquaticus) are a bottomland hardwood specialist that have experienced range contraction at the northern and western extents of their range. While swamp rabbit distribution has been studied at the northern periphery of its range, drivers of change over time have not been investigated. Here, we analyzed data collected in 2010–2012 and 2022–2023 across 16 counties in southeastern Missouri, USA and reported environmental factors driving changes in occupancy states. Occupancy probability increased between decadal surveys (0.66–0.79). Occupancy probability was negatively influenced by site isolation and patch richness density but positively influenced by site area. Colonization and extinction probabilities were influenced by bottomland hardwood forest cover change and flooding effects. When ground latrines were included, we observed an increase in detection (0.68–0.84) and occupancy probabilities (0.95–1.00). Swamp rabbit populations appear to have expanded within southeastern Missouri following many decades of range contraction.
The spectacled flying-fox Pteropus conspicillatus population has declined by 75% in two decades to become endangered. This systematic review, the first since 2011, updates knowledge of the species and identifies pressing issues in its conservation, some not recognized previously. Gaps in knowledge have been identified and, where appropriate, species phylogenetically close to P. conspicillatus have been used to inform better understanding of the focal species. Extreme heat events are now a lethal reality, habitat loss and declining condition continue, pressure to disperse roosts is pervasive, and conservation is affected by false perceptions of the species' impacts. Averting threats to this species and obtaining resources to help it recover are urgent. Priorities for action should now include surveys and characterization of roosts; modeling future heat events to inform recovery priorities; physiological studies to determine heat tolerances; developing a population growth model to inform targets for population recovery; reinstating systematic population counts; improving monitoring methods; tracking individuals over time to understand habitat use; improving understanding of diets; restoring and managing roosts in accordance with research and best practice; and improving knowledge of diseases. The article updates and revises known diet species and the number of roosts used by P. conspicillatus in Australia.
Deterrence is a key component of human-wildlife conflict management. This study firstly introduced the concept of “nonlethal pain stimulation deterrence,” a kind of deterrence technologies based on painful stimuli which do not cause severe injury to wildlife while realizing effective deterrence through precisely controlling strike intensity. Then, we conducted laser strike experiments on fresh wild boar skin samples and live individuals to assess the relationship between strike intensity and skin injury degree and individual's escape behavior, respectively. We determined the maximum laser power with minimal skin injury through skin experiments (260 W and 1 s in summer, 285 W and 1 s in winter), and the minimum deterrence values (210 W and 1 s) through live animal experiments. The strike intensity parameters determined in this study provide technical specifications for wildlife deterrence at a set distance. To improve field applicability, subsequent experiments should quantify optimal strike intensity along a distance gradient.