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Genetic ties influence the social behavior of aging animals

According to a new study led by the University of Exeter, the structure of family groups – defined in terms of “relatedness,” or the strength of genetic links to members of a social group – gives animals incentives to help or harm their social group as they age. The experts found that, when living in a group of close genetic relatives, it is in an animal’s best interest to behave in ways helping the whole group. By contrast, when living among less related, or unrelated individuals, the best strategy for individual animals often appears to be selfish or even harmful behavior.

“We wanted to know how an individual’s relatedness to their group changes as they age, and what consequences this might have for behavior,” said study lead author Sam Ellis, a research fellow in Animal Behavior at Exeter.

“We made a model to predict these changes and then tested it using data on banded mongooses, chimpanzees, badgers, killer whales, spotted hyenas, rhesus macaques, and yellow baboons. Our model fitted the real data. This is exciting is because it allows us to make predictions about how and why social behaviors can change with age.”

For instance, while male and female killer whales both remain in the same group as their mothers, with females thus having a growing number of close relatives around them as they age, female spotted hyenas usually live among fewer close relatives as time passes – features which structure these animals’ behavior towards their group members.

“Across a wide range of species, we see age-related changes in helping and harming behavior which can also differ between males and females,” explained study co-author Darren Croft, an expert in Social Evolution at the University of Leeds.

“Our new work shows that understanding how relatedness to the family group changes with age is key in understanding how the incentives to help or harm the group changes across the lifespan, which can potentially explain these differences across species and between the sexes.”

“This research opens the door for future studies by providing testable predictions for how patterns of helping and harming will change across the lifespan and we eagerly anticipate new work testing these predictions,” he concluded.

The study is published in the journal Nature Ecology and Evolution.

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By Andrei Ionescu, Staff Writer

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