Doug MacNearney, Karine Pigeon, and Laura Finnegan, Foothills Research Institute (fRI) Research Caribou Program
April 30, 2016
Executive Summary
Anthropogenic disturbance like oil and gas development is thought to negatively affect boreal caribou through displacement and degradation of habitat, and through creation of favourable conditions for other ungulates and their predators. Reproductive success may also be impacted by disturbance, and while some research has been conducted for barren ground caribou and for other ungulates, there is little knowledge regarding the effects that sensory and physical disturbance from oil and gas development may have on boreal caribou in Alberta.
We estimated the calving status (calf vs. no calf), and subsequent calf survival during the vulnerable neonatal period up to 4 weeks after calving using GPS telemetry data gathered from 62 adult female caribou from the Chinchaga and Little Smoky boreal caribou herds between 2000 and 2015. We employed an individual based method, developed using boreal caribou data from northeast British Columbia, which identifies changes in movement rates that are indicative of calving and calf mortality events. Field validation demonstrated that this approach predicts calving events and calf survival with high accuracy. We assessed site selection of adult female caribou at calving and during the calving season using a used versus available framework. We then used generalized linear mixed models to investigate habitat selection of caribou at the landscape and home range scale across six biologically defined seasons in relation to the proximity and density of anthropogenic disturbance features by type and age class. We paid particular attention to the response of caribou to oil and gas well sites due to the large fluctuations in human activity throughout the construction, drilling, producing, and post-abandonment phases of development, and the potential for differential responses of caribou to these phases. Finally, we investigated whether the calving status of individual caribou in a given year was related to the proximity and density of anthropogenic disturbance features throughout the gestational period.
We estimated 69 calving events from a total of 81 unique individual – year combinations in the Little Smoky and Chinchaga caribou ranges (85% parturition rate). Of the estimated calves born, we estimated that 52% succumbed to mortality before 4 weeks of age. Calf sites were located farther from well sites in all phases of development in both the Little Smoky and Chinchaga herd ranges, but the response to other disturbance features such as cut blocks differed between the two herds in accordance with the availability of habitat, suggesting that calf site selection is limited by the choices available to caribou in a particular range. When considering the relationship between calving status and the proximity and density of anthropogenic features, we found that in the Little Smoky range the probability of having a calf was negatively related to the overall exposure to anthropogenic disturbance density in the previous fall. This assessment would benefit from additional data to confirm this trend and allow a further investigation in Chinchaga where sample size was lower than Little Smoky. We did not find a relationship between calving status and the activity phase or proximity of well sites during the gestational period.
In our analysis of seasonal habitat selection we found that across all seasons and geographic scales and in both herds, caribou generally avoided anthropogenic disturbance at a rate greater than expected by chance. Little Smoky caribou had a higher overall exposure to disturbance within their range compared to Chinchaga caribou. The response of caribou to well sites varied slightly by phase of development and season, but overall well sites in high and moderate activity phases were avoided in Chinchaga more than well sites in the low activity phase. In Little Smoky we found a significant interaction between the phase of development and the distance to the nearest well site, with habitat selection increasing with distance from well sites in high and moderate activity phases, and remaining stable for distance to well sites in the low activity phase. Our analysis suggest that caribou avoid well sites in the high and moderate activity phases up to a distance of 3 km, however we were unable to identify a distance at which caribou stopped responding to well sites. This is potentially due to the limited availability of ‘undisturbed’ habitat, particularly in the Little Smoky range.
Overall, our detailed analyses of adult female caribou response and calving success in relation to well site status at different activity phases contributes new knowledge towards understanding the effect of anthropogenic disturbance, and associated sensory disturbance on caribou behavior. Although we did not find any clear linkages between disturbance and calving success per se, the strong patterns of avoidance by caribou of well sites in high activity phases suggests that planning the placement and timing of development of these features while also considering the spatio-temporal distribution of caribou within their ranges, may help to mitigate the negative effects of these developments on caribou in the future. In addition, calving site selection probability maps that we will provide as supplementary material (when the complete data set is analyzed) can be used by land planners and industrial partners to direct future development while considering areas preferred by caribou during the vulnerable calving season. In addition, these maps may also be used to direct habitat restoration efforts to areas where they will have the greatest benefit to caribou.
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