Nature vs. nurture: Boldness in baby fruit bats an acquired trait, not hereditary - study

Animals that are adapted to living in cities are known to be less risk-averse than those living in rural environments. The TAU team wanted to find how this trait occurs in fruit bat pups.

A baby bat with its adoptive mother (photo credit: TEL AVIV UNIVERSITY)
A baby bat with its adoptive mother
(photo credit: TEL AVIV UNIVERSITY)

Baby fruit bats behave like their adoptive mothers rather than their biological mothers, researchers from Tel Aviv University (TAU) found in a study published in the peer-reviewed journal BMC Biology in September.

Animals that are adapted to living in cities are known to be less risk-averse than those living in rural environments. The TAU team wanted to find how this trait occurs in fruit bat pups and whether it is genetic or acquired.

The researchers, led by Prof. Yossi Yovel, Head of the Sagol School of Neuroscience, and including Dr. Lee Harten, Michal Handel, Orit Dash and Nesim Gonceer of TAU and Prof. H. Bobby Fokidis from Florida's Rollins College, brought 86 pairs of fruit bats, with each pair consisting of a mother and a pup. 61 pairs were from 4 different urban colonies and 25 pairs were from 3 rural colonies.

In the first phase of the experiment, they put food inside a box that could only be accessed by adult bats who landed on top of it. The city bats were easily able to get the food, while the rural bats took several hours to figure it out.

Next, the researchers did the same thing, but this time with the baby bats. They found that, like the adult bats, the urban pups were bolder and learned faster than the rural ones, leading the team to believe these traits were inherited from the biological mothers.

Prof. Yossi Yovel, Head of TAU's Sagol School of Neuroscience (credit: TEL AVIV UNIVERSITY)Prof. Yossi Yovel, Head of TAU's Sagol School of Neuroscience (credit: TEL AVIV UNIVERSITY)

In order to determine if and how the bat pups were impacted by their mothers' conditioning, the researchers then left the pups of city-dwelling bats to be raised by rural mothers and left rural pups with urban mothers, and then studied variations in the pups' behavior, specifically regarding their boldness.

The team found that the pups tended to behave more like their adoptive mothers than their biological mothers, possibly due to higher levels of the hormone cortisol in the urban mothers' milk.

"The urban environment presents animals with more challenges and a greater variety of situations. It is therefore plausible that bats and other animals living in the city require more boldness and higher learning skills," Prof. Yovel said. "In light of our findings, we hypothesize that the [boldness] trait is passed on to pups in early stages of development, through some component of their mothers' milk."