The Egyptian Fruit Bat, or Egyptian Rousette, is a species of bat that is found throughout Africa and the Middle East. As its name projects, the fruit bat consumes large amounts of fruit each night, such as wild dates and soft fruit.
In order to feed on specific fruit trees – it tends to eat fruit that contains insects and fungus – they must fly dozens of kilometres each night and return home on the same night.
Researchers were intrigued by how these bats are able locate specific trees at night. Scientists at the Hebrew University of Jerusalem
attached miniaturized GPS devices that weigh 10 grams on the bats to study mammal navigation, according to a news release from the university
. The GPS also included a battery and memory logs.
They then tracked the movements of these bats from their cave located in Beit Shemesh over a series of consecutive nights. The bats flew in a straight line at speeds of 40 KM/H and at an elevation of hundreds of meters.
Each night, the bats went to the same tree and avoided similar trees near their cave – since they flew to specific trees, scientists ruled out smell as a navigational method.
For further analysis, researchers brought the bats to a new area in the desert where some bats were released at dusk and others at dawn. The ones released first had no difficulty locating the fruit trees, while the others “made a beeline back to the cave once they were released.”
The results of the study – published in the Proceedings of the National Academy of Sciences (PNAS)
– show that bats have an internal cognitive map of their home region, which is primarily based on visual landmarks (I.E. hills and lights).
Researchers also conclude that bats have a “large-scale navigational mechanism” and “rival those of homing pigeons.”