Wild bats instinctively catch fish

Long-fingered bats feed almost exclusively on insects, but they can also be keen fisherman, should the opportunity arise.

Ostaizka Aizpurua at the University of Copenhagen in Denmark and colleagues found this angling skill remains dormant in the bats until the right circumstances arise.

The work was published in PLOS One.

The long-fingered bat (Myotis capaccinii) is a big-nostrilled bat from Morocco, Algeria, southern Europe and the Middle East. And although the species is a widespread and devout insect-eater, some isolated populations of long-fingered bat have puzzled scientists by showing a proclivity towards fishing.

Aizpurua and her crew wanted to test how this ability to diversify food sources arose – and if it was present across the whole species.

This modification process is called “behavioural plasticity”. In this instance, it refers to an animal’s ability to broaden its diet if a new food source becomes available. It’s a bit like our ability to be flexible with cuisine choice if we’re particularly hungry.

To study the origins of this behaviour modification, the team analysed two groups of bats – individuals observed eating fish in their natural habitat and another population that stuck to insects.

“Aiming to get insight into the origin of fishing behaviour in long-fingered bats, we studied in the field the differences in sensorial and mechanical reactions to insect-like (stationary) and fish-like (temporary) prey stimuli between well-known piscivorous [fish-eating] and strictly insectivorous [insect-eating] individuals,” the researchers write.

The team found that both groups showed similar responses to fish-like prey, making longer and deeper dips when the target disappeared under the water, and also uttering a different vocalisation.

The researchers suggest these behaviours are part of the natural repertoire of all long-fingered bats.

But bats that had previously eaten fish showed a greater adeptness at this behaviour and made the switch to “fishing” behaviours much more quickly, suggesting that although the behaviours are probably innate, these skills can be improved through practice.

“All individuals seem to be mechanically and sensorially adapted to detect and capture fish, although under appropriate environmental conditions, they would further improve their technique by experience and/or social learning.”

The researchers say further research into how long these skills take to hone might shine a light on the learning processes of mammals and ongoing adaptation in nature.