Date Published: February 24, 2017
Publisher: Public Library of Science
Author(s): Victoria M. Donovan, Glen S. Brown, Frank F. Mallory, Govindhaswamy Umapathy.
Loss or alteration of forest ecosystems due to anthropogenic activities has prompted the need for mitigation measures aimed at protecting habitat for forest-dependent wildlife. Understanding how wildlife respond to such management efforts is essential for achieving conservation targets. Boreal caribou are a species of conservation concern due to the impacts of human induced habitat alteration; however the effects of habitat management activities are poorly understood. We assessed the relationship between large scale patterns in forest harvesting and caribou spatial behaviours over a 20-year period, spanning a change in forest management intended to protect caribou habitat. Caribou range size, fidelity, and proximity to forest harvests were assessed in relation to change in harvest patterns through time and across two landscapes that varied widely in natural disturbance and community dynamics. We observed up to 89% declines in total area harvested within our study areas, with declining harvest size and aggregation. These landscape outcomes were coincident with caribou exhibiting greater fidelity and spacing farther away from disturbances at smaller scales, hypothesized to be beneficial for acquiring food and avoiding predators. Contrary to our expectation that the large scale maintenance of habitat patches would permit caribou to space away from disturbance, their proximity to harvest blocks at the population range scale did not decrease through time, suggesting that movement toward landscape recovery for caribou in previously harvested regions will likely stretch over multiple decades. Caribou spatial behaviours varied across the two landscapes independently of forest management. Our study underlines the importance of understanding both changes in industry demands, as well as natural landscape variation in habitat when managing wildlife.
Anthropogenic disturbances in forested regions have altered habitat conditions for many wildlife species. Impacts to wildlife may include altered behavioural patterns [1,2], decreased abundance , and extirpation from disturbed regions , leading to an overall loss in biodiversity [5,6]. In managed forests, the fragmentation of habitat is frequently identified as having negative impacts to wildlife [7,8]. Forest management strategies may include adjusting the spatial organisation of forest harvests in an effort to maintain habitat connectivity and patch size; however, the response of wildlife and effectiveness of these strategies in unclear.
Caribou behaviours varied significantly between the two study landscapes, suggesting a broad scale adaptive response to habitat heterogeneity. These results are not atypical; previous research has documented an array of wildlife populations which display different spatial behavioural responses among landscapes (e.g. [11,57,58]). Western Ontario caribou had much smaller home range areas than eastern Ontario caribou, and also displayed much stronger summer fidelity behaviour. Our modeling effort associated smaller home range size with higher levels of harvesting within and surrounding a caribou’s home range. Animals tend to have smaller home ranges where higher quality habitat is available, meaning they do not need to travel as widely to fulfil their needs . Western Ontario may provide better quality habitat, regardless of the elevated harvesting levels we observed in comparison to the eastern study area. However, such patterns could also be indicative of higher levels of historical fragmentation in the western population range. Fragmentation can compromise caribou movement  and western Ontario caribou range has historically had much greater overlap with harvesting activities  as well as been more frequently disturbed by wildfire . Differences in disturbance regimes and habitat distributions likely similarly shape differences in predator and alternative prey distributions between landscapes [14,15]. The differences we observed in caribou behaviour are thus likely related to a number of interacting factors related to habitat distribution and abundance within each landscape as well as differences in natural and anthropogenic disturbance regimes (e.g. harvesting, mining) between regions [23,27,32,40].