Heading for the hills? Evaluating spatial distribution of woodland caribou in response to a growing anthropogenic disturbance footprint

Abstract

Anthropogenic landscape change (i.e., disturbance) is recognized as an important factor in the decline and extirpation of wildlife populations. Understanding and monitoring the relationship between wildlife distribution and disturbance is necessary for effective conservation planning. Many studies consider disturbance as a covariate explaining wildlife behavior. However, we propose that there are several advantages to considering the spatial relationship between disturbance and wildlife directly using utilization distributions (UDs), including objective assessment of the spatially explicit overlap between wildlife and disturbance, and the ability to track trends in this relationship over time. Here, we examined how central mountain woodland caribou (Rangifer tarandus caribou) distribution changed over time in relation to (i) anthropogenic disturbance, baseline range (defined using telemetry data from 1998 to 2005), and alpine habitat; and (ii) interannual climate variation (North Pacific Index; NPI). We developed seasonal UDs for caribou in west‐central Alberta and east‐central British Columbia, Canada, monitored with GPS collars between 1998 and 2013. We mapped the cumulative annual density of disturbance features within caribou range and used indices of overlap to determine the spatial relationship and trend between caribou UDs, anthropogenic disturbance, baseline range, alpine habitat, and the NPI. Anthropogenic disturbance increased over time, but the overlap between caribou UDs and disturbance did not. Caribou use of alpine habitat during spring, fall, and late winter increased over time, concurrent with a decrease in use of baseline range. Overlap between caribou UDs and disturbance increased during spring and fall following relatively cold, snowy winters (high NPI), but overall, climate did not explain changes in caribou distribution over time. We provide evidence supporting the hypothesis that caribou populations adjust their spatial distribution in relation to anthropogenic landscape change. Our findings could have implications for population persistence if distributional shifts result in greater use of alpine habitat during winter. Monitoring long‐term changes in the distribution of populations is a valuable component of conservation planning for species at risk in disturbed landscapes.

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

“…Females without calves are not restricted by the slower movement speed of their calf (Bonar, Ellington, Lewis, & Vander Wal, ; DeMars, Auger‐Méthé, Schlägel, & Boutin, ), and often have very large home ranges in summer. It is also possible that the distribution of anthropogenic disturbances, such as logging cutovers, could also influence the high degree of variation in home range size we observed in summer (Faille et al, ; MacNearney et al, ; Schaefer & Mahoney, ). The correlation we observed between home range area and social association therefore does not necessarily preclude the role of resource dispersion and abundance in explaining caribou home range size.…”

Seeking sanctuary: the neonatal calving period among central mountain woodland caribou (Rangifer tarandus caribou)

“…We constructed caribou-calving season home ranges using GPS-collar locations spanning from the start of the spring migratory period until the date of parturition. We considered 5 May and 10 May as the start of spring migration for the Narraway and Redrock-Prairie Creek herds, respectively, based on a concurrent study by MacNearney et al (2016), where seasons for these herds were defined using an individual-based recursive partitioning method that identifies transition dates between seasons based on inflection points in daily movement rates (Rudolph and Drapeau 2012). We pooled all location data from both herds to increase the sample size for the calving site selection analysis.…”

The biogeography of home range size of woodland caribou Rangifer tarandus caribou

“…In the boreal forest, caribou movements are sensitive to anthropogenic disturbance on the landscape. As disturbances mount, female caribou move less (Arlt & Manseau, ; Dyer et al., ; Rasiulis et al., ); they constrict the size of their home ranges (Beauchesne et al., ; Donovan et al., ; Ewacha et al., ; MacNearney et al., ; Smith et al., ) and, consequently, they appear to show stronger range fidelity (Faille et al., ; Lafontaine et al., ). The corollaries can be both physiological (heightened stress hormones; Ewacha et al., ) and demographic (heightened mortality; Lafontaine et al., ).…”

“…For woodland caribou ( R. t. caribou ), year‐round inhabitants of the boreal forest, home range size may reflect habitat conditions. Individuals may confine their movements and their home ranges in response to anthropogenic disturbance (Beauchesne et al., ; Donovan, Brown, & Mallory, ; Ewacha, Roth, Anderson, Brannen, & Dupont, ; MacNearney et al., ; Smith, Ficht, Hobson, Sorensen, & Hervieux, ). Among populations, too, there are pronounced differences in home range area.…”