Critical summer foraging tradeoffs in a subarctic ungulate

Area of Science:

• Wildlife Ecology
• Animal Behavior
• Conservation Biology

Background:

• Subarctic summer diets are critical for large herbivores like caribou (Rangifer tarandus granti).
• Understanding foraging behavior is challenging due to remote ranges and environmental factors like weather and insect harassment.
• Climate change adds complexity to predicting herbivore dietary shifts and habitat use.

Purpose of the Study:

• To characterize the summer behavior and diet of the migratory Fortymile Caribou Herd using GPS video-camera collars.
• To quantify the impact of insect harassment on caribou feeding behavior.
• To compare video-collar diet estimates with traditional fecal analysis methods.

Main Methods:

• Deployed GPS video-camera collars on 30 female caribou over two summer seasons (2018-2019).
• Classified 18,134 videos to categorize caribou behaviors (eating, ruminating, traveling, etc.).
• Identified consumed forages from 5,549 videos, detailing species and functional types, and compared with microhistological fecal analysis.

Main Results:

• Caribou spent 43.5% of their time eating, with behavior significantly affected by insect harassment.
• A clear tradeoff was observed between lichen and shrub consumption, with shrubs dominating in June-July as lichen use decreased.
• Video analysis identified 63 species and 70 genera of summer forages, showing strong correlation (r=0.79) with fecal analysis for forage functional types.

Conclusions:

• GPS video collars provide a powerful, high-resolution method for studying caribou foraging ecology in remote subarctic regions.
• Insect harassment significantly impacts caribou foraging efficiency, highlighting a key environmental stressor.
• Understanding dietary shifts and behavioral responses is crucial for effective conservation planning for migratory caribou populations.