Monogamy better for monkey families, study suggests

It seems there is trouble in paradise for a rare monogamous species of monkey, after a University of Derby biologist found committed couples are targeted by aggressive singles determined to break up a happy home.

For her study published in the journal PLoS ONE earlier this month (April 2013), Lecturer in Biology Maren Huck, spent almost 15 months in the sub-tropical gallery forest of Northern Argentina observing owl monkeys. The pairs of the species are, unusually for primates, monogamous.

Maren's observations of the monkey's mating system contributed to a 16 year-long study of 18 owl monkey groups with co-researcher Eduardo Fernandez-Duque, of the University of Pennsylvania (USA).

"Owl monkeys are one of a few monogamous primates who find and mate with a single partner, raising offspring together each year," said Maren.

"Little is known about this rare primate behaviour, and it is often assumed that all of the pairs and individuals in groups face little aggression or competition, once they are part of a couple. However we discovered that occasionally a 'single' owl monkey attacked a couple and replaced a partner. A phenomenon that sometimes had fatal consequences for the expelled monkey."

The study found that this went on to have significant implications for the reproductive success of the newly formed couple, with the new pair going on to produce far fewer offspring than couples who had not been parted. Monkeys with one partner for life produced 25% more infants per decade than those who had had two or more partners following a break-up.

This contrasts with other species of animals and birds, such as the kittiwake, which 'divorce', and whose lifetime reproductive success following a break-up is higher than if they remained with its original partner.

"We think this is due to the new owl monkey couple missing a reproductive season as they become familiar with one another," said Maren.

In addition to her work on the behavioural, genetic, and hormonal aspects of the mating system owl monkeys, Dr Huck has also carried out research studies that compared the behaviour and social structure of urban badgers with countryside populations, examined the physical barriers facing populations of wolves and lynx in Poland and investigated the social and genetic mating system of the moustached tamarin.