Migratory behaviours are risk-sensitive to physiological state in an elevational migrant.

Area of Science:

• Ecology
• Animal Behavior
• Physiology

Background:

• Seasonal environments pose challenges for animals, requiring adaptations like fat accretion for survival.
• Body fat levels are crucial physiological indicators that can influence animal behavior and risk assessment.

Purpose of the Study:

• To investigate the relationship between body fat and migratory behavior in Sierra Nevada bighorn sheep (Ovis canadensis sierrae).
• To test if migration is risk-sensitive to an animal's physiological state, specifically body fat reserves.

Main Methods:

• Utilized movement data from male Sierra Nevada bighorn sheep.
• Indexed physiological state by measuring body fat levels.
• Analyzed the correlation between body fat, migration probability, elevational distance migrated, and switching rates between migratory tactics.

Main Results:

• Decreasing body fat was associated with an increased probability and elevational distance of migration.
• Population-level migration switching rates were inversely related to pre-migration body fat levels.
• Observed variations in these effects across different metapopulations.

Conclusions:

• Bighorn sheep migration is demonstrably risk-sensitive to physiological state (body fat).
• Inadequate fat reserves may compel animals to trade off starvation risk for predation risk.
• Risk-sensitive migration provides behavioral flexibility crucial for long-term persistence in complex environments.