Scientists strap tiny computers to bats to listen to them hunting
The bats navigate using echolocation calls that "would be like a whisper to us.”
Bats are able to fine-tune their echolocation when hunting by controlling their flight path and call volume, a study has found.
Scientists were able to hear how bats use prey echoes for hunting by strapping tiny computers to some wild greater mouse-eared bats in Bulgaria to record their echolocation calls.
The research suggests that hunting bats narrow their sensory volumes by more than a thousand times to only focus on the prey, thereby reducing the clutter from other echoes.
“We experienced the world through the ears of the bats by recording their echoes directly on-board while they were hunting for insects at night," said lead author Dr Laura Stidsholt, from Denmark’s Aarhus University. “We wanted to use the tags to find out how bats control what they ‘see’ when they hunt tiny insects on the wing on super-fast timescales.
“We used the sound recordings to find and track echoes from prey and vegetation, and to our surprise we found that the bats are guided by extremely weak prey echoes that would be like a whisper to us.”
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According to co-author Dr Holger Goerlitz, from Germany’s Max Planck Institute of Ornithology, it’s “like an acoustic version of a tunnel vision that briefly makes their world much simpler”.
“The weak prey echoes might therefore be a consequence of the small sensory volumes shaped to hunt close to background clutter,” he said.
The research is published in the Science Advances journal.
Reader Q&A: Why are there so many species of bat?Asked by: Tamsin Nicholson, Warwickshire
There are more than 1,200 bat species in the world, accounting for almost a fifth of all mammal species. Part of the reason for this is that bats are the only mammals with flapping flight, which means that bat colonies can travel long distances and become geographically isolated from each other, splitting into separate species.
But a 2011 study at the University of Massachusetts suggested that their diversity might also be because the diets of different bat species tend to be highly specialised. This means that if a genetic mutation causes, for example, a small change in the shape of the skull or the bite force of the jaw, a bat might be able to eat a new type of fruit or insect that other bats in the area can’t handle.
This gives a big selective advantage to the descendants of this bat, and the mutation spreads. Within an evolutionary short time, the population has split into two groups and another bat species is born.