Barbastelle bats (Barbastella barbastellus) are furtive hunters. They have to be, because the moths they prey upon have developed ears to hear the bats’ echolocation calls and avoid being caught. The bats have countered this adaptation with one of their own: they use softer calls so that moths won’t hear them until it’s too late. Barbastelle calls are more than 10 times quieter than those of other bats that hunt insects with echolocation.
Researchers reported yesterday (March 14) in Functional Ecology that the bats also reduce their call volume as they close in on their prey. They tethered moths (Noctua pronuba) to a fishing rod and recorded barbastelle bats attacking them to analyze the intensity of their calls from the moths’ perspectives.
“Barbastelle bats call with surprisingly low intensity, usually a characteristic of species that hunt in cluttered habitats and need to avoid distracting echoes from branches and leaves,” says biologist Daniel Lewanzik of the Max Planck Institute of Ornithology in a press release. “Low intensity calls come at a cost though. They do not reach far and as a result, insects can only be detected from a close distance.”
D. Lewanzik, H.R. Goerlitz, “Continued source level reduction during attack in the low-amplitude bat Barbastella barbastellus prevents moth evasive flight,” Functional Ecology, doi:10.1111/1365-2435.13073, 2018.