Motion-triggered video cameras reveal spatial and temporal patterns of red fox foraging on carrion provided by mountain lions

Abstract

Carrion is a rich, ephemeral resource vital to biodiversity and ecosystem health. In temperate ecosystems in which cold temperatures and snowfall influence the accessibility and availability of small prey and seasonal mast crops, carrion may also be a limiting resource for mesocarnivores like red foxes (Vulpes vulpes), which are too small to predate ungulates. Using motion-triggered video cameras and generalized linear mixed models, we studied the spatial and temporal patterns of red fox scavenging at 232 mountain lion kills in the southern Greater Yellowstone Ecosystem (GYE) from 2012–2015. We found that red foxes scavenged mountain lion kills across all habitats throughout the year, however, red fox behaviors varied with season. In winter, we documented red foxes at a greater proportion of mountain lion kills (70.3% in winter vs. 48.9% in summer), and in greater numbers (1.83 foxes per kill in winter vs. 1.16 in summer). In winter, red foxes fed longer (= 102.7 ± 138.3 minutes feeding in winter vs. = 39.7 ± 74.0 in summer), and they more often scavenged while the mountain lion was nearby. We speculated that red foxes may have increased risk taking in winter due to hunger driven by resource scarcity. Our research highlighted an important ecological relationship between red foxes and mountain lions in the GYE. Mountain lions tolerate high levels of scavenging, so the frequency and intensity of red fox scavenging at their kills may not impact mountain lions, but instead facilitate the dispersion and benefits of resources created by this apex predator. Large carnivores, and mid-trophic felids like mountain lions in particular, are essential producers of carrion vital to biodiversity and ecosystem health. In turn, scavengers play critical roles in distributing these resources and increasing the heterogeneity of resources that support biodiversity and ecosystem structure, as well as ecological resilience.

Scavenging by fishers in relation to season and other scavengers

“…Large carcasses can provide substantial food with no handling costs compared to the small‐ and medium‐sized prey fishers usually kill and consume (LaPoint, Belant, & Kays, 2015). Fishers visited carcasses more frequently (34% of carcasses) and fed for twice as long in winter than in summer, as do other mesocarnivores (e.g., red fox, Vulpes vulpes ; Selva, Jedrzejewska, Jedrzejewski, & Wajrak, 2005; O'Malley et al, 2018). Fishers exhibit delayed implantation, rapid fetal growth in the final month of pregnancy, and give birth in late winter (mean date of parturition across their range is 25 March; Green et al, 2018).…”

“…Carrion, especially large carcasses, is a nutritious and inexpensive resource that benefits many organisms (Inagaki et al, 2020; Sebastián‐González et al, 2020). Carrion may be more important for animals experiencing resource scarcity (Barrio, Hik, Bueno, & Cahill, 2013; O'Malley, Elbroch, Lendrum, & Quigley, 2018; Prugh & Sivy, 2020), but visiting carcasses also poses risks, especially for smaller vertebrate scavengers that may be injured or killed by larger scavengers or the carnivores that killed the prey. These risks can be species‐specific, and how individuals of a species respond to risk can determine how frequently they scavenge and how much nutrition they gain from carrion (Allen, Elbroch, Wilmers, & Wittmer, 2015; Sivy, Pozzanghera, Grace, & Prugh, 2014).…”

“…We analyzed four primary variables: (a) whether fishers detected each carcass we placed in different habitats; (b) how long the first fisher took to detect a carcass; (c) the total duration fishers fed at each carcass; and (d) the temporal patterns of fishers scavenging, comparing the time of day when fishers initially visited carcasses to the time of day for subsequent visits. We then evaluated the importance of habitat characteristics (Elbroch, Lendrum, Allen, & Wittmer, 2015), presence of other scavengers (Sebastián‐González et al, 2020), and season (O'Malley et al, 2018) on the scavenging behaviors of fishers.…”

Untrapped potential: Do bear hunter cameras accurately index nontarget species?

“…As monitoring methods and technology improve, our understanding of animal distributions and resource use becomes more comprehensive. This is especially true for remote cameras, which have proven to be an effective tool for occupancy as well as spatial, and temporal, patterns of multiple species (Candler, Severud, & Bump, 2019; O'Malley, Elbroch, Lendrum, & Quigley, 2018; Wang, Allen, & Wilmers, 2015). Remote cameras have also proven effective in characterizing species use of black bear ( Ursus americanus ) and white‐tailed deer ( Odocoileus virginianus ) hunter bait sites (Bowman, Belant, Beyer, & Martel, 2015; Candler et al, 2019).…”

“…spatial, and temporal, patterns of multiple species (Candler, Severud, & Bump, 2019;O'Malley, Elbroch, Lendrum, & Quigley, 2018;Wang, Allen, & Wilmers, 2015). Remote cameras have also proven effective in characterizing species use of black bear (Ursus americanus) and white-tailed deer (Odocoileus virginianus) hunter bait sites (Bowman, Belant, Beyer, & Martel, 2015;Candler et al, 2019).…”