Experimental warming alters migratory caribou forage quality

Area of Science:

• Ecology
• Climate Change Biology
• Animal Nutrition

Background:

• Global caribou and reindeer (Rangifer) populations are declining due to various stressors.
• Arctic warming increases tundra shrub quantity but its impact on forage quality for Rangifer is unknown.
• Forage quality is critical for Rangifer body condition and reproductive success.

Purpose of the Study:

• To investigate the impact of experimental summer warming on the quality of forage available to the Bathurst caribou herd.
• To assess changes in nutrient content, phenolics, and fiber in key Rangifer forage species under warming conditions.
• To understand how warming-induced forage quality changes affect Rangifer adaptability and conservation needs.

Main Methods:

• Utilized experimental greenhouses over 8 years in the Canadian Low Arctic to simulate summer warming.
• Measured leaf forage quality and digestibility of Betula glandulosa at six intervals during the growing season.
• Analyzed five other common vascular plant and lichen species for forage quality in late summer.

Main Results:

• Experimental warming reduced Betula glandulosa leaf nitrogen by approximately 10% in early to mid-growing season.
• Warming increased phenolic concentrations by 38% in the graminoid Eriophorum vaginatum, reducing its forage quality.
• Warming had mixed effects on the lichen Cetraria cucullata, increasing nutrients and decreasing fiber but also raising phenolic content.

Conclusions:

• Warming-induced changes in forage quality and species-specific responses emphasize the importance of Rangifer diet adaptability.
• Early-season reduction in Betula glandulosa nitrogen content is a concern for calf growth.
• Demonstrated significant warming impacts on forage quality, underscoring the need for effective Rangifer range conservation to support adaptability in a changing Arctic environment.