Nathusius' bats optimize long-distance migration by flying at maximum range speed

Area of Science:

• Zoology
• Animal Migration
• Bioenergetics

Background:

• Aerial migration is a rapid but energy-intensive mode of seasonal movement.
• Understanding the energetic demands of migration is crucial, especially for bats.
• Specific data on the energy requirements for bat migration is limited.

Purpose of the Study:

• To investigate the energetic cost and flight speed of the long-distance migratory Nathusius' bat (Pipistrellus nathusii).
• To determine the optimal traveling speed for long-distance migration in this species.
• To compare flight speeds in captive bats with those observed in wild populations.

Main Methods:

• Measured flight metabolism in relation to airspeed using wind tunnel experiments.
• Inferred maximum range speed (optimal traveling speed) from metabolic data.
• Compared captive bat flight speeds with field observations of wild Pipistrellus nathusii.

Main Results:

• A U-shaped relationship between flight metabolic power and airspeed was observed in most captive bats.
• The average flight metabolic rate was 0.98±0.28 W, consistent with allometric predictions.
• Wild Nathusius' bats migrated at an average speed of 6.9±0.7 m/s, which falls within the inferred optimal range speed.

Conclusions:

• Nathusius' bats appear to migrate at an energetically optimal speed.
• Observed migratory speeds suggest that aerial refueling may not significantly reduce the bats' travel velocity.
• The findings provide valuable insights into the bioenergetics of bat migration.