Evidence for an Adaptive, Large-Scale Range Shift in a Long-Distance Terrestrial Migrant

Area of Science:

• Ecology
• Animal Behavior
• Climate Change Adaptation

Background:

• Long-distance migrations are key adaptations for mobile terrestrial animals in seasonal environments.
• Understanding migratory animals' resilience to rapid environmental change and adaptation mechanisms is crucial.
• Arctic regions are experiencing rapid warming, impacting wildlife habitats and behaviors.

Purpose of the Study:

• To investigate a dramatic shift in the wintering range of the Western Arctic Herd of caribou (Rangifer tarandus).
• To analyze the adaptive significance and drivers of this range shift in response to environmental changes.
• To understand the role of collective memory and decision-making in caribou migration patterns.

Main Methods:

• Documented a shift of over 500 km in the wintering range of the Western Arctic Herd between 2012 and 2020.
• Analyzed nearly 200 documented mortality events in relation to the range shift.
• Correlated overwinter survival rates in different habitats with migration patterns and collective memory.

Main Results:

• Caribou shifted from maritime tundra to mountainous areas for wintering.
• Overwinter survival in the maritime tundra declined significantly, while mountainous areas offered intermediate, less variable survival.
• The range shift partially mitigated increased mortality but did not fully reverse it, with evidence of poorer winter nutrition.
• Collective memory of poor preceding winter conditions was a strong predictor of southward migration.

Conclusions:

• The Western Arctic Herd's range shift demonstrates adaptive behavior in response to rapid environmental change.
• Collective decision-making and memory play a significant role in fitness outcomes for highly mobile species facing dynamic environments.
• While adaptive, the range shift highlights the challenges migratory animals face in fully compensating for climate change impacts.