Researchers at Tel Aviv University found that adopted fruit bat pups behave like the adoptive mother
What influences our behavior as adults? Heredity or the environment? And what happens to those who grew up and were not raised by their biological parents? Bat researchers at Tel Aviv University conducted a 'cross-adoption' experiment - urban fruit bat pups adopted by village mothers, and vice versa - with the aim of testing whether the trait of boldness, which characterizes urban bats, is genetic or acquired. The findings revealed that the adopted puppies behave like the adoptive mothers, and not like the biological mothers: puppies adopted by an urban mother are bolder, more inclined to take risks, and learn faster than those born in the city but adopted by a mother living in the countryside.
Is courage innate or acquired?
The study is the first of its kind conducted in bats, and also the first time that the 'environment versus heredity' question has been examined for the boldness trait in urban animals. It was carried out under the leadership of Prof. Yossi Yuval, Head The Sagol School of Neuroscience, Friend School of Zoology in the George S. Wise Faculty of Life Sciences, and the Steinhardt Museum of Nature, along with Dr. Lee Hartan, Nassim Gonchir, Michal Hendel and Orit Dash from Prof. Yuval's lab, and Prof. H. Bobby Poukidis from the University of Arizona.
"We asked to check whether boldness is transmitted from the mother, learned through the experience of the individual, or arises from genetic inheritance. The results of the study imply that the trait is transferred to the puppy in some way from the mother who raises and nurses it - even if she is not its biological mother," reveals Prof. Yuval, the leader of the study, which was recently published in the journal B.M.C. Biology.
Dr. Hartan explains: "Most animals do not live in the urban environment, but certain species actually thrive in it, and we are trying to understand how they do this. Fruit bats are an excellent example of a species that has adapted well to the man-made urban environment. Thriving colonies of fruit bats exist in Tel Aviv and other cities, at the same time as colonies that continue to exist in wild areas. It is known that one of the characteristics of animals that adapt to life in the city is boldness and willingness to take risks. In our research, we sought to examine in laboratory conditions whether this behavior is genetic or acquired."
The city bat and the village bat
The researchers brought 86 pup and mother pairs of fruit bats to the laboratory and divided them into two groups: 61 pairs from 4 urban colonies, and 25 pairs from 3 colonies located in a rural area. In a series of experiments they examined behavioral differences between the groups, with special emphasis on the bats' tendency to take risks, or if you will, how bold they are.
In a preliminary experiment, the researchers placed food inside a device that required the adult bats to land and go inside to reach the desired food. They found that the city bats rose to the challenge immediately and without difficulty, while the villagers hesitated at first, learning how to get to the food only after a few days. "Similar differences were previously discovered in studies on birds: it was found that birds that live in the city are bolder than their counterparts that live outside the city. Our study is the first to examine this issue in bats," says Prof. Yuval.
Now the researchers wanted to check if that boldness (or lack thereof), is an innate trait or is it acquired as part of the bat's adaptation to life in the city. To do this, they conducted the exact same test on the young bat pups who were still being fed by their guardians and had never foraged independently in the environment where they were born. The researchers discovered that, like their parents, the urban puppies are bolder and learn faster than their country counterparts. Prof. Yuval: "These findings seem to imply that the trait of boldness is innate, and that the urban puppies inherit it genetically from their parents. However, a young puppy was exposed to its mother, so we decided to check if it is affected or learns from her even after birth."
When you grow up you will be brave and bold like me. Mother and pup of fruit bats (photo: Yuval Barkai)
The challenging life of the big city
To test this, the researchers performed a 'cross adoption': puppies born to urban mothers were raised by rural mothers, and vice versa. "We found that the puppies behave like the adoptive mother, and not like the biological mother," explains Dr. Harthan and continues, "The meaning is that it is an acquired trait and not innate, transferred from the mother to the puppy in some way. We hypothesize that the trait may be transmitted to the pup through some component in the mother's milk." In another experiment, the researchers found that the level of the hormone cortisol is higher in the milk of urban mothers compared to rural mothers, but it is still not possible to determine with certainty that this is the mechanism of intergenerational transmission.
"The urban environment presents animals with more challenges and a wider variety of situations, therefore bats and other animals that choose to live in the city are required to develop greater courage and learning capacity" concludes Prof. Yuval. "In our research, we focused on elf cubs to examine whether the bold behavior is the result of genetics, environment, or a combination of the two. In light of the findings, we believe that the trait is passed on to the cubs through an ingredient in the milk they suck from the mother in the initial stages of development." And Dr. Harthan adds: "We believe that a deep understanding of the needs and behavior of urban animals will help in the future to protect them and adapt urban development to their needs."
More of the topic in Hayadan:
