Prey availability and ambient temperature influence carrion persistence in the boreal forest

Abstract

Scavenging by vertebrates can have important impacts on food web stability and persistence, and can alter the distribution of nutrients throughout the landscape. However, scavenging communities have been understudied in most regions around the globe, and we lack understanding of the biotic drivers of vertebrate scavenging dynamics. In this paper, we examined how changes in prey density and carrion biomass caused by population cycles of a primary prey species, the snowshoe hare Lepus americanus, influence scavenging communities in the northern boreal forest. We further examined the impact of habitat and temperature on scavenging dynamics. We monitored the persistence time, time until first scavenger, and number of species scavenging experimentally‐placed hare carcasses over four consecutive years in the southwestern Yukon. We simultaneously monitored hare density and carrion biomass to examine their influence relative to temperature, habitat, and seasonal effects. For the primary scavengers, we developed species‐specific scavenging models to determine variation on the effects of these factors across species, and determine which species may be driving temporal patterns in the entire community. We found that the efficiency of the scavenging community was affected by hare density, with carcass persistence decreasing when snowshoe hare densities declined, mainly due to increased scavenging rates by Canada lynx Lynx canadensis. However, prey density did not influence the number of species scavenging a given carcass, suggesting prey abundance affects carrion recycling but not necessarily the number of connections in the food web. In addition, scavenging rates increased in warmer temperatures, and there were strong seasonal effects on the richness of the vertebrate scavenging community. Our results demonstrate that vertebrate scavenging communities are sensitive to changes in species’ demography and environmental change, and that future assessments of food web dynamics should consider links established through scavenging.

Predicted climate‐induced reductions in scavenging in eastern North America

“…Our results highlight an overall reduction in the frequency of scavenging in the lower latitudes of our study area into the future, suggesting the behavior of the species present will change but also parallels other findings that suggest many species distributions are shifting poleward with the climate (Buckley et al, 2018; Chen et al, 2011; Hastings et al, 2020). Our findings also support observations from other regions that suggest climate change can have complex and context‐specific influences on vertebrate scavengers (Hidasi‐Neto et al, 2019; Olson et al, 2016; Peers et al, 2020; Selva et al, 2005; Stiegler et al, 2020).…”

“…These climatic conditions likely facilitate both the dependence on carcasses and their accessibility. Colder, sub‐zero temperatures can freeze carcasses solid, and deep snow can further limit smaller mammals' ability to access carrion (Peers et al, 2020). A frozen carcass is also likely more difficult to smell, and therefore locate, as low temperature delays decomposition (Moleón et al, 2014).…”

The Purr‐fect Catch: Using accelerometers and audio recorders to document kill rates and hunting behaviour of a small prey specialist

“…Whether the interest is in documenting functional responses, predator-prey interactions or population and food web dynamics, understanding and estimating kill rates and hunting success is a necessary component (Kalinkat et al, 2013;Lima, 2002;McGhee et al 2013). In addition to kill rates, estimates of hunting success, kleptoparasitism and scavenging in natural systems are key to predator energy budgets (Pagano et al, 2018), species interactions (Gorman et al, 1998;Peers et al, 2020) and food web dynamics (Focardi et al, 2017;Wilson & Wolkovich, 2011). While current methodological approaches provide estimates of kill rates and predator behaviour summarized at the population level and over seasonal time frames (Lake et al, 2013;O'Donoghue, Boutin, Krebs, Zuleta, et al, 1998), there is considerable interest in documenting predator responses to environmental change at the individual level across short temporal scales (e.g.…”

Scavenging by fishers in relation to season and other scavengers

“…For example, pumas, bobcats, and coyotes kill fishers (Gabriel et al, 2015) and fishers in our study system were sometimes killed by pumas while scavenging from deer killed by these apex predators (Allen, Elbroch, Casady, & Wittmer, 2015; Allen, Elbroch, Wilmers, & Wittmer, 2015). The mix of positive and negative interactions at carcasses may be indicative of the complexity of interspecific interactions that can occur within vertebrate scavenging communities (Peers et al, 2020; Prugh & Sivy, 2020; Sebastián‐González et al, 2020).…”