Consistent Individual Differences and Plasticity in Migration Behaviour of Three North American Ungulates

Area of Science:

• Ecology
• Animal Behaviour
• Evolutionary Biology

Background:

• Migratory herbivores rely on synchronized timing between spring migration and plant green-up for optimal foraging.
• Changes in plant green-up timing due to climate shifts challenge this synchronization.
• Herbivore populations may respond through phenotypic plasticity or evolutionary adaptation.

Purpose of the Study:

• To quantify plasticity and individual variation in spring migration timing in response to plant green-up.
• To investigate selection for high-quality forage based on green-up timing.
• To understand how North American ungulates manage migration timing in a changing environment.

Main Methods:

• Utilized behavioral reaction norms to analyze migration timing in three North American ungulate species.
• Assessed plasticity in arrival and departure dates from winter and summer ranges.
• Quantified repeatability of migration timing.

Main Results:

• Spring arrival to summer range, but not winter range departure, showed plasticity in response to green-up timing.
• Both arrival and departure timings were found to be repeatable across individuals.
• Suggests herbivores adjust migration pace to synchronize with plant availability.

Conclusions:

• Herbivores synchronize migration with plant green-up by modulating their migration pace.
• Individual differences in migration timing provide a buffer against environmental changes.
• Understanding plasticity and variation is key to predicting species' fate in a changing world.