Modular switches shift monarch butterfly migratory flight behavior at their Mexican overwintering sites

Area of Science:

• Animal Behavior
• Ecology
• Neuroethology

Background:

• Eastern North American monarch butterflies undertake long-distance seasonal migrations.
• Migratory behaviors, including sun-dependent flight, are observed during fall and spring migration.
• The transition in migratory behavior at overwintering sites remains poorly understood.

Purpose of the Study:

• To investigate the behavioral states of monarch butterflies at their overwintering sites.
• To determine how monarchs transition between migratory and overwintering behavioral states.
• To identify the underlying mechanisms of flight propensity and orientation control.

Main Methods:

• Utilized a modified Mouritsen-Frost flight simulator to test monarch butterflies.
• Collected data from monarchs during their fall migration and at Mexican overwintering sites.
• Analyzed individual directionality, group orientation, and flight propensity.

Main Results:

• Fall migratory monarchs exhibit sustained flight propensity and direction-based flight reinforcement.
• Overwintering monarchs show reduced flight propensity and lose individual directionality, resulting in loss of group orientation.
• Overwintering monarchs orient axially in a time-of-day dependent manner, suggesting local directional heading.

Conclusions:

• Migratory flight behavior in monarchs involves dynamic, state-dependent switches for flight propensity and orientation.
• These behavioral modules are controlled in a season- and location-dependent manner.
• A model is proposed where modular control governs migratory flight dynamics.