Temporal variation in habitat use, co-occurrence, and risk among generalist predators and a shared prey

Abstract

Generalist predators typically have broad diets, but their diets may become constrained when one species of prey becomes disproportionately available. Yet there is poor understanding regarding whether generalist predators exhibit stereotypic relationships with pulsed prey resources. We used telemetry data from 959 woodland caribou (Rangifer tarandus caribou (Gmelin, 1788); 146 adult females, 813 calves), 61 coyotes (Canis latrans Say, 1823), and 55 black bears (Ursus americanus Pallas, 1780) to investigate how two generalist predators interacted with caribou neonates on the island of Newfoundland. We examined the similarity of patterns of habitat use between caribou and their predators across time and related this similarity to interspecific spatiotemporal co-occurrence and mortality risk for caribou neonates. The similarity in habitat use between coyotes and caribou mirrored variation in juvenile hazard risk, but had weak association with actual co-occurrence with caribou. Bears and caribou exhibited less similarity in habitat use during the calving season than coyotes and caribou. The relationship between habitat use of bear and caribou did not correspond with either co-occurrence patterns or overall risk for caribou neonates. Our work illustrates how risk for a prey species can be shaped differently based upon differences between the behavioural strategies of generalist predator species.

Space use and social association in a gregarious ungulate: Testing the conspecific attraction and resource dispersion hypotheses

“…Although no data exist on encounter rates among caribou and their predators in our study area, for females with calves‐at‐heel, predation risk during summer when calves are a few months old could suggest that some female caribou with very large home ranges move longer distances after encountering predators. Evidence also exists suggesting that caribou avoid risky habitat (Bastille‐Rousseau, Rayl et al, ) and that caribou dyads are more likely to stay together when risk of predation is high, especially in winter (Lesmerises et al, ). Taken together, predation is likely an important driver of both social association and space use and although we were unable to incorporate aspects of predation in our study, we encourage future studies to simultaneously model effects of predation on social association and space use in caribou.…”

“…To assess seasonal differences in our response variables, we subset GPS fixes into discrete 48‐day periods that reflect winter (15 January–3 March) and summer (15 July–1 September). We chose these dates for two reasons: (a) to ensure resource distribution was relatively predictable within season (heterogeneous during the winter and homogeneous during the summer); and (b) to ensure that caribou space use in winter and summer, respectively, was not impacted by behaviors during adjacent seasons (i.e., calving season: typically May–June; mating season: typically September–October; Bastille‐Rousseau, Rayl et al, ). We did not collar all female caribou in the herds, however, we assumed that our sample of collared animals was random.…”

Habitat segregation between brown bears and gray wolves in a human‐dominated landscape

“…We defined two study periods in late winter and spring to take into account the marked seasonal variation in the annual cycle of wolves and bears (Figure 3), because seasonality is an important factor to consider in studies of interspecific interactions (e.g. Basille, Fortin, Dussault, Ouellet, & Courtois, 2013;Bastille-Rousseau et al, 2016). During the late-winter period (1 March-30 April), male bears start to leave their winter dens (Manchi & Swenson, 2005).…”

Carnivore space use shifts in response to seasonal resource availability

“…Our work builds on the limited literature available (Schmidt and Ostfeld , Bastille‐Rousseau et al. ) examining these responses. Investigating how multiple predators simultaneously respond to variation in resources can provide important insight into life history strategies and other factors shaping animal space use that research using more traditional single‐species approaches could not obtain.…”