Baby monkeys speed through childhood to avoid being killed by adult males, according to a new study on wild ursine colobus monkeys.
Researchers at the University of Ontario monitored the behavior of nine groups of wild ursine colobus monkeys from 2007 to 2014 and found that babies facing greater risks of being killed by adult males developed faster than their safer counterparts.
"Infanticide occurs in many animals, including carnivores like lions and bears, rodents like mice, and in primates," said lead researcher Iulia Bădescu, a Ph.D. candidate in evolutionary anthropology at the University of Toronto, according to a university release.
"Typically, an adult male kills an infant sired by another male so that he can mate with the mother and sire his own infants with her," she explained.
Bădescu and her team tracked the development of ursine colobus monkeys by studying changes in their fur color. Researchers explain that colobus babies are born with white fur that turns grey after a few weeks and then black and white between two and five months.
Study observations revealed that the fur of baby monkeys at greater risk of infanticide changed quicker from white to grey to black and white.
"We found that infants facing a greater risk of infanticide developed faster than infants facing lesser risk," said co-researcher Pascale Sicotte of the Department of Anthropology and Archaeology at the University of Calgary.
Previous studies on infanticide behavior revealed that babies living in groups with multiple males are more likely to be killed.
Researchers hypothesize that mothers of babies at risk of infanticide may invest more energy in their infants in a short time span to speed development.
"We know that infanticide is the result of an evolutionary arms race, where males compete with each other for reproduction and try to influence females in mating with them," Sicotte added. "In species where it happens more often, it can certainly influence the nature of the social relationships between males, as well as between males and females."
"Infant males are at greater risk of infanticidal attacks because killing a male infant not only gives reproductive access to the mother, but also eliminates a future sexual rival for the infanticidal male and his future offspring," Bădescu explained.
Researchers said the next step would be to understand how the mother perceives the threat of infanticide and the exact mechanism by which they help accelerate infant development.
The findings are published in the journal Animal Behaviour.
