Spring phenology drives range shifts in a migratory Arctic ungulate with key implications for the future

Area of Science:

• Ecology
• Climate Change Biology
• Wildlife Ecology

Background:

• Annual variation in phenology significantly affects animal behavior and survival.
• Climate change is advancing spring phenology globally, necessitating research into animal responses.
• Migratory barren-ground caribou (Rangifer tarandus) face challenges with short Arctic summers and shifting seasonal events.

Purpose of the Study:

• To investigate the influence of spring phenology on the behavior and space-use patterns of the Porcupine Caribou Herd (PCH).
• To examine how snow melt and vegetation growth affect current and future PCH distributions.
• To project potential shifts in PCH habitat use under future climate change scenarios.

Main Methods:

• Quantified PCH selection for snow melt and vegetation phenology using machine learning models.
• Determined how phenological selection drives annual shifts in PCH space-use.
• Projected future PCH distributions based on climate-driven phenology models.

Main Results:

• Caribou exhibited strong, scale-dependent selection for snow melt and vegetation growth.
• During calving, caribou selected greener, snow-free areas at finer scales within broader landscapes.
• During post-calving, caribou preferred vegetation with intermediate biomass indicating high forage quality.
• Annual phenology variation predicted major shifts in PCH space-use, with early springs favoring Alaska and late springs favoring Yukon.
• Projected climate change advances spring phenology, shifting PCH distributions westward into Alaska.

Conclusions:

• Caribou selection for specific phenological stages drives significant annual shifts in space-use.
• Future climate change is likely to alter PCH calving and post-calving distributions.
• Maintaining sufficient suitable habitat is crucial for caribou behavioral plasticity and adaptation to changing environments.