Journal of Animal Ecology最新文献

Home range (HR) is a key indicator of animal spatial ecology. HR size, shape, location and habitat composition reflect both species' ecological requirements and their responses to anthropogenic stressors. Felidae, a charismatic taxon, faces escalating threats mainly due to habitat degradation and human-wildlife conflict. Understanding the ecological and anthropogenic drivers of HR size variation is therefore critical for their conservation. To address this gap and explore these factors at a global scale for the entire taxon, we used the HomeRange database-a global database with HR values across 960 different mammal species-complemented with about 20% additional records, to compile 1137 individual HR size estimates from 29 out of 40 recognized wild felid species. We applied generalized linear mixed models to assess the influence of intrinsic, methodological, ecological and anthropogenic factors on space use. HR size was shaped by multiple drivers. It increased with body mass (0.94 ± 0.16; p < 10^-8) and was larger in males than in females (0.51 ± 0.07; p < 10^-13), consistent with higher energy demands and sex-specific reproductive strategies. HR size decreased with increasing productivity (-0.37 ± 0.07; p < 10^-7) and felid richness (-0.24 ± 0.10; p = 0.02), suggesting reduced spatial requirements in resource-rich areas and under interspecific competition. HR size also decreased with increasing croplands (HR: -0.50 ± 0.14; p < 10^-3) and pastures (HR: -0.16 ± 0.07; p = 0.02)-both human footprint proxies-which may reflect multiple causes such as anthropogenic food sources, habitat loss or movement restriction from infrastructures associated with agriculture. Our results reinforce the role of well-known established HR size's predictors such as body mass, sex and primary productivity while highlighting the impact of less frequently investigated factors (i.e. felid richness and agricultural land-use). Our findings emphasize the importance of incorporating a broad range of biological, environmental and methodological predictors when studying space use across a taxonomic group. Our approach provides novel insights into habitat requirements and the effects of anthropogenic pressures, which can ultimately lead to improved conservation strategies for felids.

Some animals exhibit large-amplitude fluctuations with periods close to their generation length. These fluctuations can be caused by seasonal environmental influences, scheduled pesticide applications, or ecological factors such as intraspecific regulation and consumer-resource interactions. While theory provides various mechanisms for how environmental and ecological factors might generate generational fluctuations, there has never been a field experiment testing the relative contributions of seasonal demographic synchronisation and intraspecific regulation to generation cycles in natural populations. The smaller tea tortrix, Adoxophyes honmai, is a serious pest of tea plants and a temperate multivoltine insect that undergoes 3-5 large-amplitude generation cycles each year under natural conditions in Japan. Theory suggests that these fluctuations may represent limit cycles driven by asymmetric intraspecific interference, where older larvae directly affect younger ones. However, in the field, these populations also experience strong seasonality and periodic insecticide applications that are thought to either generate or modify these fluctuations. We conducted a replicated field-cage experiment on the tortrix populations to manipulate the initial degree of stage synchrony and the timing of introduction. The experiment included four treatments contrasting pulsed versus continuous age structures at the onset of spring, along with two introduction timings separated by 20 days (approximately half a generation time). We minimised artificial interventions, such as harvesting and insecticide application, as well as the effect of natural enemies while allowing meteorological influences during the season. To compare the field-cage experiment results with theoretical predictions, we constructed an age-structured population model featuring asymmetric larval interference. We executed simulations using the same introduction scenarios as in the field-cage experiment. We observed the emergence of clear generational cycles in all treatments of the field-cage even in the absence of any initial demographic synchrony. This suggests an internal mechanism regulating population cycles, possibly intraspecific interference. However, the generational cycles in the field-cage were synchronised across treatments and with outer field populations. The results from the field-cage experiment and simulation analyses indicate that external environmental factors, such as precipitation, acted as a pacemaker for the generational cycles created by the internal regulatory mechanism.

Environmental stochasticity poses significant challenges to population persistence. A key mechanism thought to buffer populations against such variability is demographic buffering-the ability of a population to stabilise growth despite temporal fluctuations in survival, development or reproduction. However, empirical tests of demographic buffering remain limited and often yield conflicting results. Here, we propose an integrative demographic framework that combines two complementary approaches to identify demographic buffering: (1) stochastic elasticities, which quantify the sensitivity of long-term stochastic growth rates (λ_s) to variance in demographic processes, and (2) second-order derivatives of deterministic growth (λ₁), which indicate whether selection acts to reduce or amplify variance in vital rates. Applying this framework to 43 natural populations across 37 mammalian species, we position each species along a variance continuum and assess whether those with low stochastic elasticities-suggestive of buffering-also exhibit signs of concave selection on key demographic processes. While most primates and a few other long-lived mammals occupy the buffered end of the continuum, only one species-the Columbian ground squirrel-exhibits strong support for our hypothesis, with key vital rates both critical for λ₁ and under concave selection. In contrast, primates, despite showing low stochastic elasticities, often show convex or absent second-order effects on their most influential vital rates, indicating a mismatch between ecological buffering and evolutionary constraint. Our findings suggest that demographic buffering is more dynamic and context dependent than previously recognised. Selection does not consistently act to reduce variance in key demographic processes, even in species where population growth appears robust to environmental variability. This decoupling implies that evolutionary and ecological signals of buffering may not always align. Our framework offers a new lens to dissect the demographic and selective processes underpinning resilience, providing a scalable tool for exploring demographic strategies across taxa. Future work integrating phylogenetic context, trait covariation and environmental drivers will be essential to understand the adaptive value of demographic buffering under global change.

Theoretical and empirical studies agree that populations harbour extensive among-individual variation in phenotypic plasticity, but the mechanisms generating and maintaining this variation are often unknown. Endocrine systems, which can change plastically in response to environmental variation, may be shaped by natural selection, but their evolution requires heritable variation. It is currently unknown if endocrine plasticity in response to environmental challenges is heritable. We investigated this question in house sparrows, Passer domesticus, by testing glucocorticoid responsiveness to food restriction. We alternated restricted (70% of individual daily food intake) and adequate (110%) treatments twice, drawing blood samples at the end of each treatment. Based on glucocorticoid responsiveness, we classified individuals into high-plasticity, low-plasticity and medium (control) groups by selecting the 20 most responsive, least responsive and random individuals, respectively. We transferred these groups into separate aviaries and let them reproduce. In the next generation, we measured hormonal responsiveness using identical methods. Using a cross-foster design and quantitative genetic models, we partitioned the heritability of glucocorticoid responsiveness into genetic and environmental components. We found moderate heritability (h² > 30%) of glucocorticoid plasticity in response to food availability. The environmental and residual variances of glucocorticoid responsiveness were smaller than those for the intercept. Our findings provide empirical evidence for the existence of heritable individual variation in glucocorticoid plasticity, highlighting its potential to evolve under natural selection, particularly in dynamic and rapidly changing environments.

Temperature is a key ecological factor influencing biological processes across various levels of biological organization. At the individual level, temperature changes often impact life-history traits. The Temperature-Size Rule predicts lower body mass at higher temperatures, whereas the Metabolic Theory of Ecology predicts faster growth rates and shorter development times with rising temperature via its effects on metabolism. Butterflies, a highly diverse group distributed worldwide, often exhibit plastic responses to differences in ambient temperature. As such, climate change may potentially impact their life history traits, population dynamics and interactions. We conducted a Bayesian multilevel meta-regression of 71 studies published between 1960 and 2024, encompassing 673 effect sizes, to assess the impact of temperature variation on butterfly growth rate, development time and body mass across ontogenetic stages and sexes. Our meta-analysis reveals that rising temperatures markedly accelerate growth and shorten development time in butterflies at a rate of ca. 10%/Δ°C, while body mass is comparatively only weakly affected. These temperature effects on growth and development are consistent across sexes and life stages and are largely independent of evolutionary history, suggesting a basis in fundamental biochemical constraints. These patterns highlight the potential for climate change to reshape butterfly life cycles, population dynamics and ecological interactions.

Savanna ecosystems support unique biodiversity and provide livelihoods for millions of people. Yet, wild herbivores are in decline due to poaching and land-use change while livestock numbers are increasing. These changes in density and composition alter savanna vegetation. There are likely indirect cascading effects of altered vegetation on savanna arthropods, but our understanding is limited despite their pivotal role in ecosystem functioning. We evaluate how differences in mammalian herbivory affect terrestrial arthropods in a semiarid Kenyan savanna. We sampled ground-active arthropods (focusing on ants) in six herbivory treatments ranging from high-intensity herbivory to complete exclusion of large herbivores. Ant abundance and richness were not affected by herbivory treatments, but the community composition of ants and arthropods differed at extremely high and low levels of herbivory due to indirect impacts on vegetation. Community composition changes occurred under extremely high levels of herbivory because the resulting short-grass communities and patches of bare ground led to high species turnover in ants. By contrast, extremely low herbivory promoted woody encroachment that led to the loss of savanna specialists via both species turnover and nestedness. We conclude that cascading effects of mammalian herbivory play only a relatively small role in shaping savanna arthropod communities, except at extreme levels of herbivory. However, the occurrence of savannas with these extreme levels of herbivory, both high and low, is likely to increase in the future, which may lead to more widespread changes in ecosystem functioning as a consequence of shifts in arthropod community composition.

Environmental variability shapes species' population dynamics. Yet, the mechanisms linking environmental changes to individual-level metrics (e.g. foraging behaviour, body condition) and reproductive outcomes in the wild remain poorly understood. Energetics play a central role in mediating trade-offs between self-maintenance and reproduction under fluctuating environmental conditions. As such, it provides a powerful framework for identifying how individual responses to environmental variation scale up to influence population dynamics. Using a unique long-term monitoring and bio-logging dataset spanning over 25 years providing continuous measures of diving behaviour, feeding activity and daily energy expenditure, this study investigates how individual responses to environmental variation affect population dynamics. Focusing on Adélie penguins (Pygoscelis adeliae) during the energetically demanding chick-rearing phase, we integrated individual-level foraging and energetics data with colony-wide reproductive metrics to elucidate how environmental cues lead to life-history trade-offs. Winter sea-ice conditions exhibited a quadratic relationship with key individual behavioural and energetic parameters. Specifically, increased sea-ice concentration and delayed ice retreat led to longer foraging trips, reduced time spent diving and poorer body condition. At the population level, while energy expenditure was not associated with changes in reproductive outcome, increased foraging effort (time spent feeding per day) led to enhanced fledging success. Adverse on-land conditions, such as higher snowfall, had negative impacts on reproductive outcomes. These findings support the central role of energy as a common currency of maintenance and reproduction. By linking individual energetics to demographic performance, our work advances our understanding of how energy allocation strategies in response to environmental stressors shape population dynamics. These insights are crucial for improving predictive models of population trajectories and offer valuable guidance for conservation strategies aimed at mitigating the impacts of global change on ecosystems.

The influence of parasite infection on host thermal tolerance remains poorly understood. To address this, we investigated how infection with the trematode Himasthla elongata affects survival and heat shock protein expression in the blue mussel Mytilus edulis following repeated exposure to heat stress in a simulated intertidal environment. Two groups of mussels with experimentally induced low (55.3 $\pm$ 35.6 metacercariae per mussel) and high (148.6 $\pm$ 78.2 metacercariae per mussel) infection levels were exposed to air (31°C, 33°C or 35°C) for 2 h over 10 days to simulate a tidal cycle. Survival was assessed daily. In addition, the mRNA expression level of three heat shock genes (hsp24, hsp70 and hsp90) was assessed in mussels exposed to 17°C and 33°C for 2 h over a three-day period. Dissection confirmed clear differences in infection levels between groups. Survival decreased significantly with increasing air temperature, but in the 35°C treatment, mussels with high infection levels exhibited a near-significant increase in survival. Expression of hsp24, hsp70 and hsp90 increased with rising air temperatures, and high infection levels significantly upregulated hsp90. Although trematode infection did not significantly increase survival, our results suggest that trematode infection can protect against thermal stress by upregulating specific heat shock proteins in M. edulis. The hsp responses point to a parasite-induced tolerance mechanism, potentially through stress priming or frontloading, and highlight an overlooked role of parasitism in mediating thermal resilience in intertidal ecosystems.

Research Highlight: Journal of Animal Ecology, 00, 1-13. https://doi.org/10.1111/1365-2656.70182. Beyond rising temperatures, several parts of Africa are affected by aridification (more frequent and worsening droughts, lengthening dry seasons). Such drier conditions are likely to affect in several ways not only the many large herbivore species but also the rich carnivore guild that characterise African savannas, with consequences on the behavioural ecology of predator-prey interactions. Using data sets of exceptional quality on the feeding behaviour and the reproduction of leopards and lions covering 4 years of contrasting environmental conditions in a semi-arid African savanna, Balme et al. analysed the effect of drought conditions on the carnivores' diet composition, kill rates, prey biomass acquisition but also cub production and survival. They showed that droughts led to a higher prey biomass consumption for the two carnivore species although the underlying mechanisms differed (higher kill rate for leopards and larger consumed prey for lionesses). Additionally, they revealed that the probability of cub survival was driven by factors other than drought-driven food acquisition (such as intraguild predation by hyaenas for leopards and sarcoptic mange for lions). Balme et al. (2025) convincingly showed that droughts influence not only predator-prey interactions through several pathways, but also carnivore intraguild interactions. Altogether, their findings illustrate the difficulty to predict the impact of drier conditions on carnivore populations if we do not better unravel the mechanisms through which climate change affects both predator-prey and predator-predator interactions. Overall, this inspiring study invites us to conceptualise a larger framework to study interspecific interactions in African mammals in a context of a drier (and hotter) climate.

As a result of human-induced environmental change, animals increasingly face challenges that differ from those encountered throughout their evolutionary history. While this has caused dramatic declines for many species, some can persist by gathering information to reduce uncertainty, thereby minimising risks and exploiting new opportunities. The strategic use of social information can be particularly useful in enabling such uncertainty reduction. Here, we argue that the behavioural and affective states of others provide vital social information for animals to guide evaluations of risks and opportunities. Specifically, attending and responding to indicators of others' affective states through processes such as emotional contagion may facilitate information transmission. For instance, when exposed to a novel, ambiguous anthropogenic stimulus that could indicate either an opportunity or a threat, animals may use social information about others' affective states to decide whether to approach or avoid the stimulus. To increase immediate and long-term benefits, individuals might also alter their social behaviour and information use flexibly based on critical early-life experiences, the socio-ecological context or the behaviour and states of associates in the social network. Finally, given that an individual's affective state can influence how it copes with changing environments and makes appropriate decisions, we argue that there is a need for greater synergy between animal welfare and conservation efforts. Bridging the gap between ensuring individual-level welfare and population-level resilience will be crucial for ethical policies to protect wild animals responsibly in the face of human-induced rapid environmental change.