This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A mother bat has one crucial challenge: find her own babies among hundreds of other bats in the colony. Making sure she cares for and nurses only her own offspring is important to ensuring their survival.
Among Japanese house bats, mothers keep track of their pups using the babies' isolation calls. To understand how these calls affect the mothers, the researchers monitored changes in the heart rates of mother bats presented with calls from their own babies and other bats' babies. Although the mother bats didn't react to calls from other bats' pups, the sound of their own pups made their hearts beat faster.
"The inspiration for our study began with a striking observation in our laboratory colony. When a pup was separated from their roosting area, only the biological mother immediately rushed over to bring it back," said Dr. Kazuki Yoshino-Hashizawa of Doshisha University, lead author of the article in Frontiers in Ethology.
"We knew that pups emit isolation calls—acoustic distress signals—when separated. But seeing this strict behavioral selectivity made us wonder: What is happening inside the mother when she hears these calls?" The scientists captured four pregnant bats from a colony roosting near Doshisha University. Each bat gave birth to a litter of three pups.
When the pups were 2 days old, the scientists recorded samples of their isolation calls. Because some of the litters contained no females, the scientists recorded calls from only male pups to rule out any variation based on the sex of the pup. "Isolation calls are specific vocalizations emitted by pups when they are separated from their mothers, functioning like a human baby's cry," said Yoshino-Hashizawa.
"When a pup is lost or separated in a dark colony, these calls alert the mother to locate them. Pup calls have individual signature features, allowing mothers to tell them apart." The pups grew quickly: At about 8 days old, they started to produce their first echolocation calls, and after about 12 days they all stopped uttering isolation calls. By the time they were 30 days old, they were able to fly and produce echolocation calls like adults, and they no longer roosted next to their mothers.
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