Journal of Animal Ecology最新文献

Research Highlight: Allison, A., Conway, C., Goldberg, A., Morris, A., and Hakanson, E. (2025) Seasonal body mass dynamics mediate life-history trade-offs in a hibernating mammal. Journal of Animal Ecology. https://doi.org/10.1111/1365-2656.70160. Body mass is an important proxy of individual state, especially for animals in seasonal environments. Storage of energy, primarily as fat, decouples daily energy expenditure from current food availability, providing flexibility in how animals respond to temporal variability in conditions and resources. Hibernating mammals take this to the extreme among endotherms: By fattening extensively and entering prolonged bouts of energy-saving torpor, they can remain inactive for part of the year, which maximises their chances of survival until the productive season. Allison et al. (2025) used a large data set of annual body mass change to investigate among-individual variation in the extent and timing of pre-hibernation fattening, its ecological co-variates and survival consequences in the endangered northern Idaho ground squirrel (Urocitellus brunneus). Delayed fattening was a cost of reproduction for females. Relatively fat squirrels had increased survival over the hibernation season, which is likely explained by fatter individuals choosing to enter hibernation earlier to avoid predation risk, rather than an energetic constraint imposed by a short growing season. Allison et al. found support for hypotheses relating fattening dynamics to thermal conditions, conspecific density and possibly time limitation, but not to limited food availability or interspecific competition. These results provide insight into state-dependent behavioural decisions about activity in seasonal environments and their consequences for life-histories in an unusual model among endotherms. They are important also for informing management actions to help conserve this endangered species.

Rapid expansion of human activities has altered abiotic and biotic environments and reshaped the sensory systems of animal species. Auditory perception, a key sensory component of soniferous species, is essential for signal detection, species recognition and group coordination. Birds mitigate acoustic masking in fragmented habitats by actively modulating the spectral and temporal features of their songs. However, it remains challenging to determine whether these modulations are primarily driven by biotic factors (e.g. species interactions within varying community compositions) or by abiotic factors (e.g. island attributes). We surveyed bird communities on forested islands in the Thousand Island Lake region, China, using passive acoustic monitoring. We applied sound frequency-based analyses to examine the relationship between island attributes (area and isolation), acoustic assemblage composition (species richness, morphological and phylogenetic relatedness) and sound frequency modulation of birds on 12 islands. Our findings indicated that species competition within acoustic space led to various strategies of frequency modulation to avoid acoustic overlap. With increasing frequency overlap, birds exhibited greater variations in peak frequency and frequency range, reflecting decoupled modulation in which vocal adjustments occurred either upward or downward, depending on context. By disentangling the effects of community composition from island attributes, we found that acoustic overlap was intensified on remote and small islands, particularly among species with large body size or close phylogenetic relationships, driving acoustic niche partitioning. These findings highlight the importance of biotic interactions within animal communities in driving avian vocal production shifts, emphasizing the necessity of jointly considering community composition and gradients of abiotic factors when examining sensory adjustments.

Climate change is increasing the frequency, intensity and duration of droughts. While much is known about the effects of drought on herbivores, its impact on carnivore ecology and demography remains poorly understood. Drought may benefit large carnivores by increasing prey vulnerability but can also increase intra- and interspecific interactions and competition. We assessed how a severe drought influenced the diet, space use and reproduction of leopards and lions in South Africa's Sabi Sands Game Reserve, focussing on their contrasting ecology and dominance. Despite an increase in energetic gain, leopard reproductive success declined significantly during the drought, primarily due to increased vulnerability of cubs to intraguild predation. Lions also increased their net energetic gain during drought and, while they showed a marginal increase in cub survival, this was offset by a mange outbreak. These findings challenge the conventional assumption that drought universally benefits large carnivores. For leopards, a subordinate carnivore, the top-down pressures of competition and predation outweighed bottom-up benefits of prey vulnerability. Lions, the dominant competitor, benefitted from increased prey vulnerability and decreased intraspecific conflict but remained vulnerable to stochastic external factors. This underscores the complex interplay of environmental stress, predator interactions and reproductive success, with important implications for carnivore conservation under increasing drought frequency and severity in semi-arid systems.