Understanding predation risk and individual variation in risk avoidance for threatened boreal caribou

Abstract

Predation risk is a driver of species’ distributions. Animals can increase risk avoidance in response to fluctuations in predation risk, but questions remain regarding individual variability and the capacity to respond to changes in spatial risk across human‐altered landscapes. In northeast British Columbia, Canada, boreal caribou populations declined as roads and seismic lines have increased, which are theorized to increase gray wolf predation. Our goal was to model risk and to evaluate individual variability and the development of risk perception by examining individual risk avoidance in response to reproductive status and age. We used locations from collared caribou and wolves to identify landscape features associated with the risk of a potential wolf‐caribou encounter and risk of being killed given an encounter. We built resource selection functions to estimate individual responses to risk. We used general linear regressions to evaluate individual risk and linear feature avoidance as a function of age and reproductive status (calf or no calf). Linear features increased the risk of encounter. Older caribou and caribou with calves demonstrated stronger avoidance of the risk of encounter and roads, but weaker avoidance in late summer to the risk of being killed relative to younger and calf‐less individuals. Mechanisms explaining the inverse relationships between the risk of encounter and risk of being killed are uncertain, but it is conceivable that caribou learn to avoid the risk of encounter and roads. Responses by females with vulnerable calves to the risk of encounter and risk of being killed might be explained by a trade‐off between these two risk types and a prioritization on the risk of encounter. Despite the capacity to alter their responses to risk, the global decline in Rangifer populations (caribou and wild reindeer) suggests these behaviors are insufficient to mitigate the impacts of anthropogenic disturbances.

Corridors or risk? Movement along, and use of, linear features varies predictably among large mammal predator and prey species

“…If anthropogenic LFs are associated with risk, we predict that individuals avoid these features and move faster while on them. In our system, we expect to observe these patterns in both ungulate species (caribou and moose), with a magnitude reflecting their respective vulnerability to wolf predation (DeMars & Boutin, ; Mumma et al, ). Lastly, if anthropogenic LFs provide subsidies, as is the expectation for bears, another dominant predator in our system (Dawe, Filicetti, & Nielsen, ; Finnegan, MacNearney, & Pigeon, ; Tigner et al, ), we predict that individuals select these features and move slowly when they are on them.…”

“…These patterns can be used to generate predictions about movement behaviours responses if they are hypothesized to provide resources or protection, be used as travel corridors, impede movement or are associated with risk predator use of anthropogenic linear features (LFs) such as roads, pipelines, railroads and seismic lines (long narrow cutlines created for oil and gas exploration) increases predator search rates and facilitates access into caribou habitat, thus increasing the likelihood of incidental caribou kills Dickie, Serrouya, McNay, et al, 2017;Houle, Fortin, Dussault, Courtois, & Ouellet, 2010;James & Stuart-Smith, 2000). While the influence of human disturbance on behavioural responses by wolves is increasingly well documented, the responses of other key species involved in caribou declines, such as moose, bears and caribou themselves, are less developed (but see Berger, 2007;Mumma, Gillingham, Johnson, & Parker, 2017;Tigner, Bayne, & Boutin, 2014;Vistnes & Nellemann, 2008). These knowledge gaps and inconsistencies in responses observed across temporal scales of analysis highlight the need to clarify the mechanisms underlying space-use patterns using high-resolution data.…”

Modeling multispecies predator–prey dynamics: predicting the outcomes of conservation actions for woodland caribou

“…In contrast, linear features appeared to increase the risk of predation for caribou (Mumma et al. , DeMars and Boutin ). Thus, we applied an additive mortality factor that was a linear function of the density of seismic lines and roads.…”

Effects of linear features on resource selection and movement rates of wood bison (Bison bison athabascae)

“…We demonstrated such variation as the responses of wood bison to LFs differed from those reported elsewhere for boreal caribou, two threatened ungulate species occurring sympatrically within boreal forests of western Canada. In contrast to boreal caribou, which generally avoid LFs (Dyer et al 2001;Mumma et al 2017;DeMars and Boutin 2018), wood bison were somewhat ambivalent to LFs, showing weak and variable selection or avoidance of LFs depending on land-cover type and weak seasonal selection for areas with increased LF density. These differences suggest that LFs may have a lower impact on habitat quality for bison than for caribou.…”