Caribou Diet Assessment

Conservation of boreal caribou (Rangifer tarandus caribou) populations is a focal concern in northern Alberta and across Canada’s boreal forest. Numerous factors are contributing to their decline, and one of them may be reduced lichen availability. The overall purpose of this study was to evaluate distribution of lichen across the landscape and analyze caribou winter diet composition in relation to physiological hormones and caribou habitat preferences. Specific objectives were: (1) determine composition of caribou diet in winter; (2) assess effects of diet composition and distance to winter roads on hormone indicators of nutritional and psychological stress; (3) identify geographic distribution of lichen-rich areas; (4) evaluate how lichen-rich areas and distance to winter roads influence resource selection by wintering caribou; and (5) recommend future work related to caribou-lichen relationships. Data were collected in the Egg-Pony and Algar caribou herd ranges. Gluticocorticoid (GC) and triiodothryronine (T3) were the hormones analyzed from 498 pellet samples.

Key Findings: (1) Lichen were detected infrequently, suggesting lichen-rich habitats are rare; (2) Wildfires strongly influence lichen distribution – ecosystems burned between 50 and 80 years ago contained greatest amount of lichen cover; (3) caribou diet is dominated (over 50%) by terrestrial and arboreal lichens in the winter; (4) nutritional conditions improved with more lichen in diet; (5) caribou selected sites rich in lichens and further from winter roads; (6) physiological indices show lichen-rich areas close to winter roads are stressful for caribou to access. Key Recommendations: (1) Develop long term monitoring of population change, diet (including lichens), physiological condition, and potential limiting factors; (2) conserve lichen-rich habitats and test methods to re-establish lichen rich habitats; (3) conduct trial study using imagery and/or LiDAR data at finer than 10m res to better delineate and identify lichen-rich sites that are currently poorly mapped; and (4) sample caribou nutrition and energetics as part of a long term monitoring program during snow and snow-free seasons to determine importance of summer nutrition on this caribou population.