Ear size matters
Bats navigate the dark using echolocation. Echolocation is enhanced by external ears, but external ears are thus expected to compromise flight efficiency. At the same time, previous research has suggested that large ears also produce more aerodynamic lift than small ears.
In this study, the flight lab researchers together with a Danish collegue found that both species had higher body drag than previously assumed and that the large-eared species had a higher body drag coefficient, but also produced relatively more ear/body lift than the small-eared species, in line with prior studies on model bats. The relatively higher power of the large-eared species - resulting in lower optimal flight speeds - support the notion of a trade-off between the acoustic benefits of large external ears and aerodynamic performance. The result of this trade-off would be the eco-morphological correlation in bat flight, with large-eared bats generally adopting slow-flight feeding strategies.
Read more about the study on biology.lu.se
To the paper "Body lift, drag and power are relatively higher in large-eared than in small-eared bat species", by n the Journal of the Royal Society Interface.