How Bats Find Their Pups in Complete Darkness - Space and astronomy

Research from Doshisha University shows that mother bats can distinguish their own offspring by their isolation calls, while their heart rate changes in response to specific vocalizations.

Finding a pup in a crowded bat colony is a demanding task. Mothers must identify their offspring among hundreds or even thousands of animals communicating in total darkness. A study by researchers at Japan’s Doshisha University, published in Frontiers in Ethology, examined how this recognition works and what happens physiologically when mothers hear their young.

The research focused on a colony of Alionoctula abramus, a small East Asian bat that often roosts in human-made structures such as roofs and attics. The colony lives near Doshisha University and had already been observed by the researchers in an earlier separation experiment, in which only the biological mother left the colony to search for an isolated pup.

For the new study, the team placed four pregnant females in a laboratory colony. Each gave birth to three pups. The researchers recorded the young bats’ isolation calls, vocalizations that function somewhat like a baby’s cry by attracting the mother’s attention. These calls were distinctive for each pup.

The bats’ rapid development allowed the researchers to follow the young until they became independent. After 12 days, the pups stopped producing isolation calls. By 30 days, they began sleeping apart from their mothers and had started producing adult vocalizations, which were also recorded.

The researchers then played the mothers a series of calls, including those of their own pups, unrelated pups and an unfamiliar adult. The mothers’ heart rates increased when they heard the isolation calls of their own offspring, but remained at normal levels when they heard calls from another pup. The response to their offspring also continued when the young bats produced adult calls after becoming independent.

Calls from an unfamiliar adult also caused the mothers’ heart rates to rise. The researchers said this shows that the bats’ hearts respond to the stimulus, but an electrocardiogram alone cannot establish whether the reaction is positive or negative.

The authors cautioned that the results should be confirmed with a larger sample, since the study involved only four mothers. Even so, the findings indicate that mother bats use individualized vocal cues to recognize their offspring in the darkness of the colony.

Sources: Focus.it.