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Wolves (Canis lupus) can exert top-down pressure and shape ecological communities through selective predation of ungulates and beavers (Castor Canadensis). Considering their ability to shape communities through predation, understanding wolf foraging decisions is critical to predicting their ecosystem level effects. Specifically, if wolves are optimal foragers, consumers that optimize tradeoffs between cost and benefits of prey acquisition, changes in these factors may lead to prey switching or negative-density dependent selection with potential consequences for community stability. For wolves, factors affecting cost and benefits include prey vulnerability, risk, reward, and availability which can vary temporally. We described wolf diet in by frequency of occurrence and percent biomass and characterized diet in relation to optimal foraging using prey remains found in wolf scats on Isle Royale National Park, Michigan, USA during May–October 2019–2020. We used logistic regression to estimate prey consumption over time. We predicted prey with temporal variation in cost (vulnerability and/or availability) such as adult and calf moose (Alces alces) and beaver to vary in wolves’ diet. We analyzed 206 scats and identified 62% of remains as beaver, 26% as and moose, and 12% as other (birds, smaller mammals, and wolves). Adult moose were more likely to occur in wolf scat in May, when moose are in poor condition following winter. Similarly, the occurrence of moose calves peaked June–mid July following parturition but before their vulnerability declined as they matured. In contrast, beaver occurrence in wolf scat did not change over time, possibly reflecting the importance of low handling cost prey items for recently introduced lone or paired wolves. Our results demonstrate that wolf diet is plastic and responsive to temporal changes in prey acquisition cost as predicted by optimal foraging theory. Temporal fluctuation in diet may influence wolves’ ecological role if prey respond to increased predation risk by altering their foraging or breeding behavior.

Predator-prey dynamics are a fundamental part of ecology, but directly studying interactions has proven difficult. The proliferation of camera trapping has enabled the collection of large datasets on wildlife, but researchers face hurdles inferring interactions from observational data. Recent advances in hierarchical co-abundance models infer species interactions while accounting for two species' detection probabilities, shared responses to environmental covariates, and propagate uncertainty throughout the entire modeling process. However, current approaches remain unsuitable for interacting species whose natural densities differ by an order of magnitude and have contrasting detection probabilities, such as predator-prey interactions, which introduce zero inflation and overdispersion in count histories. Here, we developed a Bayesian hierarchical N-mixture co-abundance model that is suitable for inferring predator-prey interactions. We accounted for excessive zeros in count histories using an informed zero-inflated Poisson distribution in the abundance formula and accounted for overdispersion in count histories by including a random effect per sampling unit and sampling occasion in the detection probability formula. We demonstrate that models with these modifications outperform alternative approaches, improve model goodness-of-fit, and overcome parameter convergence failures. We highlight its utility using 20 camera trapping datasets from 10 tropical forest landscapes in Southeast Asia and estimate four predator-prey relationships between tigers, clouded leopards, and muntjac and sambar deer. Tigers had a negative effect on muntjac abundance, providing support for top-down regulation, while clouded leopards had a positive effect on muntjac and sambar deer, likely driven by shared responses to unmodelled covariates like hunting. This Bayesian co-abundance modeling approach to quantify predator-prey relationships is widely applicable across species, ecosystems, and sampling approaches and may be useful in forecasting cascading impacts following widespread predator declines. Taken together, this approach facilitates a nuanced and mechanistic understanding of food-web ecology.

Habitat loss and degradation threaten forest specialist wildlife species, but some generalist mesopredators exploit disturbed areas and human-derived food, which brings them into closer contact with humans. Mesopredator release is also important for human health for known zoonotic disease reservoirs, such as Asian civets (Viverridae family), since this group includes the intermediator species for the SARS-CoV-1 outbreak. Here we use camera trapping to evaluate the habitat associations of the widespread banded civet (

Habitat loss and degradation can undermine wildlife communities and ecosystem functioning. However, certain generalist wildlife species like mesopredators and omnivores can exploit these disturbed habitats, sometimes leading to population increases (e.g. 'mesopredator release' in degraded areas). Although mesopredator release may cause negative effects on food webs and zoonotic disease management, some disturbance-tolerant species may help perpetuate important ecological interactions, such as seed dispersal. We evaluated the habitat associations of common palm civets Paradoxurus hermaphroditus, which are widespread generalist mesopredators in Southeast Asia. Common palm civets are also high-quality seed dispersers, and potential zoonotic disease hosts. We used published and new camera trapping data to map their probability of presence across Southeast Asia and evaluate regional-scale associations between capture rates and habitat variables such as elevation, ecoregion intactness and Human Footprint Index, among others. We also assessed the influence of habitat variables on their relative abundance at the local scale. At the regional scale, we found that common palm civets showed significant positive associations with landscapes characterized by lower ecoregion intactness, higher Human Footprint Index and lower elevations. At the local scale, their relative abundance showed a significant positive association with higher Human Footprint Index, but only to a certain point, after which it started decreasing. They also favoured lower elevations at the local scale. These multi-scale results indicate that common palm civets' abundance can increase under certain levels of human disturbances, consistent with the 'mesopredator release' hypothesis. This suggests they may be crucial seed dispersers in degraded forest landscapes, especially where more sensitive seed dispersers have disappeared. Our results are also consistent with previous studies reporting that habitat degradation increases populations of potential zoonotic disease hosts, and thus risks of transmission to humans.