Refuge or predation risk? Alternate ways to perceive hiker disturbance based on maternal state of female caribou

Abstract

Human presence in natural environments is often a source of stress that is perceived by large ungulates as an increased risk of predation. Alternatively, disturbance induced by hikers creates a relatively predator‐free space that may serve as a refuge. We measured the behavioral responses of female caribou to disturbance associated with the presence of hikers during summer in the Gaspésie National Park. We used those data to determine whether caribou responded negatively to human activity (i.e., the predation risk hypothesis) or whether human activity resulted in a decrease in the magnitude of perceived risk (i.e., the refuge hypothesis). Female caribou with a calf spent nearly half of their time feeding, regardless of the presence of a trail or the number of hikers. They also decreased their vigilance near trails when the number of hikers increased. Conversely, lone females fed less frequently and almost doubled the time invested in vigilance under the same circumstances. However, both groups of females moved away from trails during the day, especially in the presence of hikers. We demonstrated that risk avoidance was specific to the maternal state of the individual. Lactating females accommodated the presence of hikers to increase time spent foraging and nutritional intake, providing support for the refuge hypothesis. Alternatively, lone females with lower energetic requirements and no maternal investment in a vulnerable calf appeared less tolerant to risk, consistent with the predation risk hypothesis. Synthesis and applications: Hikers influenced the vigilance–feeding trade‐off in caribou, underlining the importance of appropriate management of linear structures and human activities, especially across the critical habitat of endangered species. Even if some individuals seemed to benefit from human presence, this behavioral adaptation was not sufficient to reduce annual calf mortality associated with predation.

Spatial factors influencing northern mountain caribou (Rangifer tarandus) survival and distribution in the Telkwa Range

“…Overall, my results suggest that it is unlikely that recreation is the primary mechanism influencing the decline of the TCH. Evidence from my research and other studies (Seip et al 2007, Lesmerises et al 2017, however, suggests that recreation will influence the distribution of woodland caribou and that such an impact can act cumulatively with other disturbances. For example, the TCH predominantly selects for highelevation habitat, likely as a strategy to avoid disturbance or greater predator densities found across valley bottoms.…”

“…It appears that roads were not associated with an increase in mortality, yet observed caribou behaviour suggested a risk Recreational use, both motorized and non-motorized, can lead to range abandonment and/or increased accessibility to caribou habitat by wolves (Bergerud 1988, Simpson 2000, Seip et al 2007, Lesmerises et al 2017. I did not detect a relationship between recreation and Telkwa caribou survival.…”

“…Second, caribou may associate certain types of development, such as roads, trails, and seismic lines, with increased predation or mortality risk. Linear features, for example, are known to increase predator efficiency and the potential for predator-prey encounters (James and Stuart-Smith 2000, Whittington et al 2011, Dickie et al 2016, Lesmerises et al 2017. Caribou, however, are known to avoid infrastructure such as mines, settlements, and cabins, which are not associated with increased predation.…”

“…For example, linear features have been correlated with wolf-induced caribou mortalities and an increase in encounter rates between wolves and caribou (Whittington et al 2011, Apps et al 2013. Some have hypothesized that winter recreation, such as backcountry skiing and snowmobiling, can result in packed snow that allows increased access by wolves to caribou habitat (Bergerud 1996, Simpson 2000, Powell 2004); however, a correlation between recreational activity and caribou survival has yet to be established (but see Lesmerises et al 2017). …”

“…To date, research on the potential effects of recreation on caribou has predominantly focused on changes in animal behaviour or population distribution (Mahoney et al 2001, Reimers et al 2003, Seip et al 2007. The relationship between recreational activities and caribou survival has yet to be investigated (but see Lesmerises et al 2017).…”