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1. Gifts of an enemy: scavenging dynamics in the presence of wolves ( Canis lupus )

   https://doi.org/10.1093/jmammal/gyab020  

   Klauder, Kaija J ; Borg, Bridget L ; Sivy, Kelly J ; Prugh, Laura R ( March 2021 , Journal of Mammalogy)

   Hopkins, Jack (Ed.)

   Abstract Carrion represents an important resource for carnivores. Examining competition for carrion in a risk–reward framework allows for a better understanding of how predator guilds compete for and benefit from carrion. We used trail camera data to compare wintertime carrion use and vigilance behavior of four carnivores in Denali National Park and Preserve. We found that carrion use was dominated by wolves (Canis lupus) and wolverines (Gulo gulo), followed by red foxes (Vulpes vulpes) and coyotes (Canis latrans). Wolves and wolverines were twice as likely to visit a carcass as foxes and coyotes, and their visits were longer and more numerous. Our results suggest scavenging animals reduced their risk exposure primarily by reducing their use of carrion, with some evidence of increased vigilance at busy sites. We found that carrion use and behavior at carcass sites were influenced by the mortality type of the carcass, the age of the carcass, and the long-term intensity of wolf use in the area. Our results also suggest that wolves are the “top scavenger,” and indicate that intraguild competition for carrion strongly affects which species benefit from carrion, with larger and more aggressive species dominating. 

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2. Human disturbance increases trophic niche overlap in terrestrial carnivore communities

   https://doi.org/10.1073/pnas.2012774117  

   Manlick, Philip J. ; Pauli, Jonathan N. ( October 2020 , Proceedings of the National Academy of Sciences)

   Animal foraging and competition are defined by the partitioning of three primary niche axes: space, time, and resources. Human disturbance is rapidly altering the spatial and temporal niches of animals, but the impact of humans on resource consumption and partitioning—arguably the most important niche axis—is poorly understood. We assessed resource consumption and trophic niche partitioning as a function of human disturbance at the individual, population, and community levels using stable isotope analysis of 684 carnivores from seven communities in North America. We detected significant responses to human disturbance at all three levels of biological organization: individual carnivores consumed more human food subsidies in disturbed landscapes, leading to significant increases in trophic niche width and trophic niche overlap among species ranging from mesocarnivores to apex predators. Trophic niche partitioning is the primary mechanism regulating coexistence in many communities, and our results indicate that humans fundamentally alter resource niches and competitive interactions among terrestrial consumers. Among carnivores, niche overlap can trigger interspecific competition and intraguild predation, while the consumption of human foods significantly increases human–carnivore conflict. Our results suggest that human disturbances, especially in the form of food subsidies, may threaten carnivores by increasing the probability of both interspecific competition and human–carnivore conflict. Ultimately, these findings illustrate a potential decoupling of predator–prey dynamics, with impacts likely cascading to populations, communities, and ecosystems.

    

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3. Intraguild dynamics of understudied carnivores in a human‐altered landscape

   https://doi.org/10.1002/ece3.6290  

   Easter, Tara ; Bouley, Paola ; Carter, Neil ( April 2020 , Ecology and Evolution)

   Mesocarnivores constitute a diverse and often abundant group of species, which are increasingly occupying hweigher trophic levels within multi‐use landscapes. Yet, we know relatively little about their interactions with each other, especially in human‐altered areas. Using camera trap data collected in a forestry concession in the Greater Gorongosa ecosystem of central Mozambique, we examined the spatiotemporal relationships and potential for intraguild competition among three understudied African carnivores: African civets (Civettictis civetta), bushy‐tailed mongooses (Bdeogale crassicauda), and large‐spotted genets (Genetta maculata). After accounting for habitat preferences and tolerance to anthropogenic factors, we found that African civets and bushy‐tailed mongooses avoid each other spatially and temporally. Additionally, civets and mongooses were also both more likely to use sites farther away from human settlements, possibly decreasing the total available habitat for each species if competition is driving this spatial partitioning. In contrast, we did not find evidence for spatial or temporal partitioning between large‐spotted genets and African civets, but bushy‐tailed mongooses altered their activity patterns where they co‐occurred with genets. Our study contributes to scant ecological knowledge of these mesocarnivores and adds to our understanding of community dynamics in human‐altered ecosystems.

    

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4. Predators balance consequences of climate‐change‐induced habitat shifts for range‐shifting and resident species

   https://doi.org/10.1111/1365-2656.13631  

   Shepard, Isaac D. ; Wissinger, Scott A. ; Wood, Zachary T. ; Greig, Hamish S. ( November 2021 , Journal of Animal Ecology)

   While many species distributions are shifting poleward or up in elevation in response to a changing climate, others are shifting their habitats along localized gradients in environmental conditions as abiotic conditions become more stressful. Whether species are moving across regional or local environmental gradients in response to climate change, range‐shifting species become embedded in established communities of competitors and predators. The consequences of these shifts for both resident and shifting species are often unknown, as it can be difficult to isolate the effects of multiple species interactions.

   Using a model system of insects in high‐elevation ponds in the Rocky Mountains of Colorado, we sought to disentangle the effects of predation and intraguild interactions on the survival and development of a semi‐permanent pond resident caddisflyLimnephilus externusand the habitat‐shifting caddisAsynarchus nigriculusthat is being forced into semi‐permanent ponds as temporary ponds dry too quickly to complete development.

   We conducted a manipulative in‐situ pond cage experiment in whichL. externusandA. nigriculuscaddisfly larvae in single‐species treatments and together were exposed to the presence/absence of predatoryDytiscusdiving beetle larvae. This approach allowed us to isolate the effects of intraguild interactions and predation on the survival and development of both the resident and habitat‐shifting species.

   We found that intraguild interactions had strong negative effects on the resident and habitat‐shifting species. Intraguild interactions reduced the survival of the residentL. externusand increased the variation in survival of the shiftingA. nigriculus. However,Dytiscuspredators reduced these negative effects, stabilizing the community by increasingL. externussurvival and reducing variation inA. nigriculussurvival. We also found that intraguild interactions reducedL. externusbiomass but resulted in increasedA. nigriculusdevelopment.A. nigriculusdevelopment was also increased by predation.

   Our results show that strong intraguild interactions between resident and shifting species are likely to have negative consequences for both species. However, the presence of predators reduces these negative consequences of the habitat shift on both the resident and the shifting.

    

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5. Can a mesocarnivore fill the functional role of an apex predator?

   https://doi.org/10.1002/ecs2.4383  

   Avrin, Alexandra C. ; Pekins, Charles E. ; Wilmers, Christopher C. ; Sperry, Jinelle H. ; Allen, Maximilian L. ( January 2023 , Ecosphere)

   As keystone species, apex predators play a role in structuring most ecosystems through competition and facilitation, thereby affecting community structure, prey abundance and behavior, vegetation, and abiotic processes. Apex predators are also highly threatened and have been extirpated from much of North America, leading to mesocarnivores, such as coyotes (Canis latrans), becoming de facto apex predators in many ecosystems. However, it is unknown if these mesocarnivores can fill the same functional keystone role as true apex predators. We compared the spatial and temporal habitat use of mesocarnivores in two similar study systems, one with pumas (Puma concolor) and one without, to determine how the role of coyotes in structuring the carnivore community changes in the absence of pumas. We used multispecies occupancy and relative abundance models to examine the spatial avoidance of pumas and coyotes by the smaller mesocarnivores, and temporal overlap and avoidance‐attraction ratios to examine temporal avoidance. We found that coyotes partially fill the functional role of apex predators, but with weaker effects than pumas. Where pumas were absent, site use intensity and relative abundance increased for coyotes (180% and 1250%) and raccoons (Procyon lotor, 308% and 3273%) and decreased for bobcats (Lynx rufus, 36% and 55%), gray foxes (Urocyon cinereoargenteus, 13% and 32%), and striped skunks (Mephitis mephitis, 3% and 12%). Coyotes and raccoons shifted their temporal activity away from pumas, while gray foxes shifted their activity closer to pumas. Detection likelihood decreased for all species after detection of a puma (67%–93%) or coyote (46%–94%) in both sites, but small mesocarnivores avoided pumas more than coyotes in the study area with both. Interactions between carnivores are complex and best understood with multiple measures and in the context of the full community. While coyotes appear to suppress smaller mesocarnivores by some measures (e.g., temporal avoidance), they do not by others (e.g., spatial avoidance) and have overall weaker effects than pumas. Our results suggest that coyotes are not a substitute for apex predators, and conserving true apex predators is likely important for maintaining ecosystem health.

    

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