Journal of Animal Ecology最新文献

Research Highlight: Oli, M., Kenney, A., Boonstra, R., Boutin, S., Murray, D., Jung, T., Hines, J., Krebs, C. (2026). Demographic mechanisms of snowshoe hare population cycles in Yukon, Canada. Journal of Animal Ecology. https://doi.org.10.1111/1365-2656.70169. Ecologists have long been intrigued by cycles in population abundances characterizing the dynamics of some wild species. Abundance may follow surprisingly regular cycles, with an increase phase, a peak phase and then a decline phase of more or less the same length. Predator-induced mortality has long been proposed as the main demographic mechanism inducing population cycles, leading most of cycle theory to consider that population cycles result from survival changes only. In this paper, Oli et al. (2025) assessed how the cycles in population abundance of the snowshoe hare (Lepus americanus) in Yukon, observed during 43 years, are driven by survival or reproductive rates of some specific age classes and how their contributions differ according to the cyclic phase. Thanks to the individual monitoring of more than 7000 snowshoe hares and a state-of-the-art capture-mark-recapture modelling framework, they showed different contributions of age-specific vital rates to the population growth rate, depending on the cyclic phase (increase, peak, decline and low phases) and the breeding period considered (early, mid, late and non-breeding periods). For instance, improved breeding probability, litter size and pre-weaning survival played a major role during the increase phases, whereas lower pre-weaning survival explained population decline. They also highlighted a strong interaction between season and cyclic phases, with, for example, at mid-breeding season, a survival in low phases that is close to the survival observed in increase phases. This led to different life-history strategies over the seasons and the phases: the population had a fast strategy in the early breeding season in the increase phase and a slow strategy in the late breeding season and decline phase, demonstrating a high level of plasticity across phases and seasons. The enigma of population cycles is not fully solved yet, but the study by Oli et al. (2025) clearly contributes to improving our mechanistic understanding of population cycles.

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.