In early summer, the females of certain bat species gather in what are called maternity colonies, to give birth. In these abandoned caves or mines, the number of bats can easily double, with a population totaling thousands of individuals. How does a female manage to recognize her baby?
One step at a time
Bats living in big colonies use different cues to identify their young: spatial memory, sound, smell, touch and sight.
Finding a baby in all that space
As soon as she arrives in the cave, the bat uses her spatial memory. She can tell if her little one is near the entrance or the back, on the left or on the right. And she heads towards that area.
Vocalizing to get reconnected
Next come the auditory cues. Young bats are like humans: they make noise. From birth, the young one twitters and its mother answers with various vocalizations. Mother and baby learn to recognize each other very early on through what’s known as isolation calls. To locate her baby in the cave, the female emits an echolocation call. In the crush of an extremely dense colony, a baby can recognize its mother at a distance of one meter just by the sound. It will reply with an isolation call, which brings mother and child back to each other. That behavior can be observed in two of our chiroptera: the little brown bat (Myotis lucifugus) and the big brown bat (Eptesicus fuscus).
Every bat has its own smell
Finally, in the last moments, olfactory clues guarantee recognition of the young one. In fact, females and their babies have numerous scent glands. In certain species, the submandibular gland grows by 25 percent in the first few days after birth. When she leaves her cave, the mother rubs that gland against her baby’s face, which makes it that much easier for her to spot it when she comes back. Here again, the smell is slightly different from one bat to another.
Finally, in our little brown bat (Myotis lucifugus) and our eastern pipistrelle (Pipistrellus subflavus), tactile memory is important. Just before leaving her baby, the female will carry out some grooming on it, and does the same thing on her return. This behavior stimulates recognition of individuals, but it also facilitates defecation and urination in the young one.
In fact, bats are like us. They use their memory and their senses. For us, their cries are no more than a mix of cacophonic noises, but for them this is a real form of communication.