Lesser short-nosed fruit bat. Photo by Anton Croos via National Geographic.
Bats represent an enormous amount of the mammal species alive today, but we still have a lot to learn about them. We have direct experience with a particularly large species of fruit bat called the Indian flying fox or Greater Indian Fruit Bat, and we’ve also learned earlier this year about insectivore bats in Thailand that can protect rice paddies from pests. Now we hear that fruit bats, contrary to prior scientific belief in much of the bat-biology community, can also use sonar echolocation to navigate the way insect-eating bats do. Whereas all insectivorous bats use vocal projections of sound to echolocate and find prey, most fructivorous bats have large eyes that they use to locate fruit or nectar. Three species of the fruit-eaters, however, have now been shown to use a very crude and relatively inaccurate form of echolocation using clicks created by their wingbeats. National Geographic writer Ed Yong reports:
Together with Sara Bumrungsri and Yossi Yovel, [Arjan Boonman] studied the cave nectar bat, as well as the lesser short-nosed fruit bat and the long-tongued fruit bat. He found that as the animals flew in a pitch-black tunnel, they all made audible clicks. The clicks aren’t accidents of flight. The team showed that the bats can adjust the rate of these sounds, and they click more furiously when flying in the dark than in dim light. Perhaps they actually use these noises to find their way around.
To test this idea, the team released the bats into a room containing a dozen inch-thick hanging cables. This kind of obstacle course is a classic of bat research, and echolocating species can easily weave their way around the cables. The fruit bats could not. Despite their clicks, they crashed often.
But the team didn’t give up. They trained a dozen cave nectar and short-nosed bats to discriminate between two big metre-wide boards: a harder one that’s great at reflecting echoes, and a cloth-covered one that absorbs more sound. Visually, the boards were similar; acoustically, worlds apart. And the bats could tell. They quickly learned to land on the right target and did so 7 times out of 10.
To read the full original article from NatGeo’s Phenomena section, click here.
