Aerial migration is the fastest, yet most energetically demanding way of seasonal movements between habitats.
Aerial migration is the fastest, yet most energetically demanding way of seasonal movements between habitats. A new study led by scientists at the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) investigated the energy requirements and travel speeds of migrating Nathusius’ bats (Pipistrellus nathusii). Using a wind tunnel experiment to determine the exact energy demands of different flying speeds and a field study to record actual travel speeds of migrating bats, the scientists demonstrated that bats travel at the speed where their range reaches a maximum, enabling them to cover long distances with a minimum amount of energy. How the researchers tracked down this cruise control is published in the “Journal of Experimental Biology”.
For many taxa, and bats in particular, scientists still lack a clear understanding of the energy requirements for migration. A team of scientists lead by Sara Troxell and Christian Voigt from the Leibniz-IZW designed an ambitious experimental study to make substantial progress on this question. The first part of the study was a wind tunnel experiment combined with measurements in a respirometry chamber. The chamber allowed the scientists to precisely track the CO2 enrichment in the air from the breath of the bats, from which they calculated the metabolic rate during flight. By repeating these measurements directly before and after one-minute flights at various speeds in the wind tunnel, the scientists recorded flight metabolic rate in relation to air speed and then calculated the flight speed with the best energy to distance ratio. The second part of the study was conducted at a migratory corridor along the Baltic Sea coast in Latvia. Using the echolocation calls of migrating Nathusius’ bats, the scientists established the flight trajectories of these bats which allowed them to measure the actual speed of migration. “Our study confirms that the observed flight speeds are consistent with the expectation that migratory bats practice optimal flight speeds for covering the largest distance with the least amount of energy”, Troxell and Voigt concluded. This speed is around 7.5 meters per second, equivalent to 27 kilometres (16 miles) per hour.
Read more at Forschungsverbund Berlin
Image: This is Nathusius' bat (Pipistrellus nathusii). (Credit: Christian Giese)
