A person trying to learn their way around a new neighborhood might look at a map. You wouldn't benefit from being carried upside-down in the dark.
The study was published last month in Current Biology. The bat pups gain skills when their mothers take them on nightly trips between caves and trees.
Bat mothers carry their young while flying, according to a behavioral ecologist at the Max Planck Institute of Animal Behavior in Konstanz, Germany. Egyptian fruit bats are attached to their mothers for the first three weeks of life. While a mother searches for food, her pup clings to her body with two feet and its jaw, sticking its teeth around her nipple. Older pups that weigh 40 percent of what they do can still be seen flying with their mothers.
It hadn't been clear why the moms go to this length instead of leaving pups in the cave where they roost, as some other species do. Dr. Goldshtein and Lee Harten were both graduate students at Tel Aviv University when they worked on this maternal mystery.
Egyptian fruit bat mothers and pups were captured by researchers. They attached a tag to each bat that contained a radio transmitter and miniature gps device. The bats were brought back to the cave.
Dr. Harten was on the roof of a 10-story building with a view of the cave to track the bats. She ordered Dr. Goldshtein to follow the radio signals of bat pairs as they flew out at night. There was a problem with the pup's movement, because the mother's signal disappeared.
Dr. Harten said that they thought they were doing their job wrong.
The image is.
A bat is flying over Tel Aviv.
They needed the data for better answers. Finding the devices themselves was a challenge because there was no way to control where the tags fell. Rats dragged them into their burrows when they landed in roads or bushes. The scientists had to go to people's homes and ask for permission to search. Dr. Goldshtein said that you need a lot of charm.
It was more than a year into their project before they realized their early results were correct. The signals of mother and baby bats differed because the mothers were abandoning their babies in trees while they hunted for food.
Dr. Goldshtein said that they couldn't imagine the mother leaving the pup on the tree.
They have been doing field work for over five years. When Egyptian fruit bats pups are a few weeks old, their mothers fly to a tree and leave them there without supervision, like a day care drop-off. The mother might come back throughout the night to nurse the pup. She takes the pup home when she is done.
The mother uses the same tree over and over. As the pup gets older and heavier, the mother shifts to a tree closer to the cave.
The mother leaves the cave when the pup is 10 weeks old. The young bat flies straight to its most recent drop-off site after emerging from the cave for the first time. The pup uses the drop-off tree as a starting point for its own exploration as it grows older.
Dr. Goldshtein said they were amazed to see the results. The baby bats hang from their mothers bellies. The authors don't know how learning works. Egyptian fruit bats can echolocate using clicks of their tongue, but they think it may be by sight.
The authors did a great job of uncovering the poorly understood interactions between mother bats and pups, said Mirjam Knrnschild, a behavioral ecologist at the Museum of Natural History in Berlin. She said that the results suggest that mothers help their pups with orientation.
Dr. Knrnschild was surprised that pups can memorize routes while being carried upside-down. She said she found it astonishing.
