Laura Finnegan, Tracy McKay, Karine Pigeon, Doug MacNearney, and Barry Nobert, (fRI Research Caribou Program)
Helen Schwantje (Government of British Columbia), Susan Kutz (University of Calgary), and Bryan Macbeth (Government of British Columbia and University of Calgary)
June 13, 2017
Executive Summary
Woodland caribou are declining across their range, mainly due to habitat disturbance and associated unsustainable rates of predation. However, caribou health and disease status are increasingly recognized as important factors in the survival and reproductive success of caribou. The goal of this two-year project was to increase understanding of mortality risk and caribou health in west-central Alberta and east-central British Columbia in the Redrock Prairie Creek, Narraway, A La Peche, and Little Smoky caribou herds. Our overall objectives were to 1) determine accurate causes of death for caribou mortality events, including the relative roles of predators, 2) investigate caribou health and disease and establish comprehensive health baselines for each caribou herd, 3) evaluate landscape-related mortality risk factors (terrain, natural disturbance, and anthropogenic disturbance), and 4) evaluate the link between predator occurrence and mortality risk. This research will provide insight into the relationships between landscape disturbance, predator occurrence, and caribou mortality events, and provides the first herd-specific baseline report of health and disease for boreal and southern mountain caribou herds in west-central Alberta and east-central British Columbia.
Between May 2013 and January 2017, we collected field data at 25 caribou mortality locations, using standardized site investigations, necropsies, and sampling protocols. We attributed 14 of these mortalities to probable predation, and we established that the predator guild for caribou in west-central Alberta and east-central British Columbia includes not only wolves, but also cougars and bears: 4 mortalities were from cougar, 4 from grizzly bear, 2 from wolf, and 3 had multiple predator signs. The remaining 11 mortalities were attributed to accidents, disease/health status, or unknown causes.
We used biological samples collected from caribou mortalities and winter fecal pellet sampling to evaluate health and disease in the Redrock Prairie Creek, Narraway, A La Peche, and Little Smoky caribou herds. From fecal pellet surveys, we detected a range of gastrointestinal parasites including Nematodes, Strongylates, tapeworm eggs, and Protostrongylid dorsal spine larvae. Prevalence of these gastrointestinal parasites was similar to prevalence previously reported for Alberta and British Columbia, and there were no apparent trends across sex or herd. Health testing from caribou mortalities revealed the presence of ectoparasites (winter tick) and bacteria (Erysipelothrix rhusiopathiae). Hair cortisol concentrations (HCC) were generally higher levels than reported for caribou elsewhere in Canada, although the method of data collection (hair collected from carcasses) makes direct comparisons difficult.
Using data collected at mortality sites along with GIS-based landscape variables, we assessed the roles of terrain and anthropogenic disturbance features in explaining caribou mortalities, including predationrelated mortalities and mortalities of unknown cause, within and outside of protected areas. Mortality locations were associated with low elevation areas and proximity to streams. Outside of protected areas, mortality risk also increased with an increase in anthropogenic linear features (pipelines, roads, and seismic lines). We used these results to produce spatially explicit surfaces of mortality risk based on models of landscape variables. Using results from previous research we produced annual probability of occurrence surfaces for wolves, grizzly bears, and cougars, and used these to assess mortality risk relative to predator occurrence. From this analysis we found that caribou mortality locations were associated with a higher probability of wolf and grizzly bear occurrence.
Overall, the results of this research project revealed that caribou predators in west-central Alberta and east-central British Columbia include cougars and bears in addition to wolves; this knowledge may have implications for management of alternate prey and predator populations in these caribou ranges. Our results also demonstrate the value of rapid mortality site investigations to accurately determine cause of death, and to collect valuable caribou health and disease data. The health and disease data gathered during this project is the first comprehensive herd-specific baseline health data collected for declining caribou herds in west-central Alberta and east-central British Columbia and provides insights into the overall health status of caribou herds in the area. These health and disease data also may be used to track changes in caribou health in the future, particularly with the expansion of moose, deer, and elk within caribou ranges, and within the context of climate change. Continued research focused on assessing and understanding caribou health may contribute to caribou recovery initiatives by identifying priority areas for restoration based on disease transmission risk, and by identifying herds that may be at highest risk of disease outbreaks. Finally, our spatially explicit surfaces of mortality risk can be used to target restoration activities to areas with the highest mortality risk within the Redrock Prairie Creek and Narraway caribou ranges, including areas of high linear feature densities and landscape disturbances located near riparian areas. In addition, the probability of occurrence surfaces we produced for wolves, grizzly bears, and cougars in the the Redrock Prairie Creek and Narraway caribou ranges can be used to target restoration activities in areas where species-specific predation risk is highest.
# 15-ERPC-08 / 16-ERPC-05