Natures wonders: migrating bats on cruise control (Introduction)

by David Turell , Friday, March 01, 2019, 01:48 (2093 days ago) @ David Turell

They may fly up to 2,000 km:

https://cosmosmagazine.com/biology/a-bat-released

'This is a Nathusius bat (Pipistrellus Nathusii) flying, and not at all stressed.

"Researchers Sara Troxell and Christian Voigt from the Leibniz Institute for Zoo and Wildlife Research in Germany recently tested a number of the bats in the field and in wind tunnels to determine the energy they expended while aloft.

"They discovered, in effect, that they are equipped with a form of cruise control. In different circumstances, the animals all selected the flight speed that would allow them to cover maximum distance and minimum energy cost.

"For the Nathusius bat, the optimal flight speed was around 27 kilometres an hour. The species, which is resident in Europe, is known to undertake journeys of as long as 2000 kilometres to reach hibernation sites.

***

"ABSTRACT
Aerial migration is the fastest, yet most energetically demanding way of seasonal movement between habitats. However, for many taxa, and bats in particular, we lack a clear understanding of the energy requirements for migration. Here, we examined the energetic cost and flight speed of the long-distance migratory Nathusius’ bat (Pipistrellus nathusii). We measured flight metabolism in relation to airspeed in a wind tunnel, inferred the optimal traveling speed over long distances, i.e. maximum range speed, and compared this value with flight speed measured in wild conspecifics. Body mass and wing morphologies were similar in captive and wild bats, indicating that the body condition of captive bats was similar to that of migratory bats. Nine out of the 12 captive bats exhibited a U-shaped relationship between flight metabolic power and airspeed when flying in the wind tunnel. The flight metabolic rate across all airspeeds averaged 0.98±0.28 W, which corresponds well to established allometric relationships between flight metabolic rate and body mass for bats. During summer migration, P. nathusii traveled at an average speed of 6.9±0.7 m s−1, which was significantly higher than the minimum power speed (5.8±1.0 m s−1), yet within the range of expected maximum range speed inferred from wind tunnel experiments. This suggests that P. nathusii may migrate at an energetically optimal speed and that aerial refueling does not substantially lower migratory speed in P. nathusii.{"

Comment: An adaptation like soaring birds on updrafts.