Baby monkeys grow faster to avoid being killed by adult males

Date: March 17, 2016

Source: University of Toronto

Natural selection has shaped the ways in which babies grow in different species, including the rate or speed with which they develop.

A new study by Canadian researchers suggests that some baby monkeys develop faster than others in the same population, and that this is best explained by the threat of infanticide they face.

The study, led by Iulia Bădescu, a PhD candidate in evolutionary anthropology at the University of Toronto (U of T), and Professor Pascale Sicotte of the Department of Anthropology and Archaeology at the University of Calgary (U of C), looked at infant development in wild ursine colobus monkeys. The study is published in the April 2016 issue ofAnimal Behaviour, and available online today.

"Infanticide occurs in many animals, including carnivores like lions and bears, rodents like mice, and in primates," said Bădescu. "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."

Black-and-white colobus includes several species of medium-sized monkeys found throughout equatorial Africa. They have black bodies with white hair that sometimes forms a bushy white beard and sideburns, or can extend down the back like a 'cape' and down the tail. They are distinguished from many other monkeys by their lack of an opposable thumb and their cow-like stomachs that allow them to digest the fibrous leaves they eat.

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