Natural regeneration on seismic lines influences movement behaviour of wolves and grizzly bears

Abstract

Across the boreal forest of Canada, habitat disturbance is the ultimate cause of caribou (Rangifer tarandus caribou) declines. Habitat restoration is a focus of caribou recovery efforts, with a goal to finding ways to reduce predator use of disturbances, and caribou-predator encounters. One of the most pervasive disturbances within caribou ranges in Alberta, Canada are seismic lines cleared for energy exploration. Seismic lines facilitate predator movement, and although vegetation on some seismic lines is regenerating, it remains unknown whether vegetation regrowth is sufficient to alter predator response. We used Light Detection and Ranging (LiDAR) data, and GPS locations, to understand how vegetation and other attributes of seismic lines influence movements of two predators, wolves (Canis lupus) and grizzly bears (Ursus arctos). During winter, wolves moved towards seismic lines regardless of vegetation height, while during spring wolves moved towards seismic lines with higher vegetation. During summer, wolves moved towards seismic lines with lower vegetation and also moved faster near seismic lines with vegetation <0.7 m. Seismic lines with lower vegetation height were preferred by grizzly bears during spring and summer, but there was no relationship between vegetation height and grizzly bear movement rates. These results suggest that wolves use seismic lines for travel during summer, but during winter wolf movements relative to seismic lines could be influenced by factors additional to movement efficiency; potentially enhanced access to areas frequented by ungulate prey. Grizzly bears may be using seismic lines for movement, but could also be using seismic lines as a source of vegetative food or ungulate prey. To reduce wolf movement rate, restoration could focus on seismic lines with vegetation <1 m in height. However our results revealed that seismic lines continue to influence wolf movement behaviour decades after they were built, and even at later stages of regeneration. Therefore it remains unknown at what stage of natural regeneration, if any, wolves cease to respond to seismic lines. To reduce wolf response to seismic lines, active restoration tactics like blocking seismic lines and tree planting, along with management of alternate prey, could be evaluated.

Close encounters of the fatal kind: Landscape features associated with central mountain caribou mortalities

“…Outside of protected areas, we found that predation risk increased closer to seismic lines across all three spatio‐temporal scales of habitat use. Previous research has shown that seismic lines are used by bears and wolves (Dickie et al., 2019; Finnegan, Pigeon, et al., 2018; Tigner et al., 2014), increase predator travel speeds and encounter rates with prey (Dickie, Serrouya, McNay, et al., 2017; McKenzie et al., 2012; Mumma et al., 2017), and are a source of forage for primary prey species (e.g., moose) and bears (Finnegan, MacNearney, et al., 2018). By assessing habitat use prior to predation‐caused caribou mortalities, our results provide direct evidence that predation risk for caribou is higher near seismic lines.…”

“…Anthropogenic disturbance can enhance predation risk by increasing the spatial and temporal overlap between predators and prey (Frey et al., 2017; Whittington et al., 2011), increasing predator travel speeds and hunting efficiency (Dickie et al., 2017; Finnegan, Pigeon, et al., 2018; McKenzie et al., 2012), or decreasing the effectiveness of prey refugia (DeMars & Boutin, 2018; Peters et al., 2013). Anthropogenic disturbance can also increase predation risk through apparent competition, where habitat change alters the abundance and distribution of primary prey, resulting in an increased abundance and distribution of predators and increased predation rates for secondary prey species (DeCesare et al., 2010; Latham et al., 2011; Robinson et al., 2002).…”

Slowing down wolves to protect boreal caribou populations: a spatial simulation model of linear feature restoration

“…, DeMars and Boutin ), and recovering vegetation on LFs provides more key bear food than the interior forest (Finnegan et al. ). Thus, incidental bear predation on caribou could be reduced to some degree by LF restoration, unless vegetation on former LFs still provides more bear food.…”

“…Whether LF restoration would reduce bear predation on caribou is still under research. Bears use LFs as traveling paths (Tigner et al 2014, DeMars andBoutin 2018), and recovering vegetation on LFs provides more key bear food than the interior forest (Finnegan et al 2018). Thus, incidental bear predation on caribou could be reduced to some degree by LF restoration, unless vegetation on former LFs still provides more bear food.…”

Caribou in the cross-fire? Considering terrestrial lichen forage in the face of mountain pine beetle (Dendroctonus ponderosae) expansion

“…For terrain, we used a LiDAR-derived depth to water estimation, a metric of soil wetness based on local topography and modeled hydrologic flow [67,68]. To represent the diminishing effect of the depth to water on vegetation growth, we transformed the variable using an exponential decay function 1 -e −1.55×Depth2Wat(m) [69]. This decay function caused depth to water to Number of transects surveyed in west-central and north-western Alberta, Canada among the five sampling strata during the summers of 2014 and 2015. a partitioned into time-since-disturbance in five year increments.…”