The wide-eyed, smiley-faced male Azara’s owl monkeys of Argentina are among the most faithful mates and best fathers in the world, according to a study that also found a strong link between fidelity and the quality of child care in 15 mammalian species.
Researchers have known that the owl monkeys stick together, but they could not be certain that the males were always the fathers of the children they so devotedly cared for. Studies with birds and other species have shown that fathers often unwittingly care for offspring that are not theirs.
Not so for the owl monkeys, says Eduardo Fernandez-Duque, the lead author of the study in the Proceedings of the Royal Society B. "The monkeys are in a monogamous relationship, the males are fully committed to caring for the offspring, and when we check the genetics, we have straight monogamy," he said. In other words, all of the offspring were descended from the caretaking males. None was the product of a promiscuous relationship.
"There is nothing like this in other primates or mammals," Fernandez-Duque said. "Every single male studied over 18 years in captivity and in the field has shown devoted care." When you see a baby riding on an adult, "you can put your money down — the adult is a male."
'No right or wrong for humans'
Is it fair to say that the owl monkeys put humans to shame?
"There is no right or wrong for humans," Fernandez-Duque said. Many human societies are monogamous, but that arose in many of those societies after the development of states, he said. Monogamy is often enforced by the state, but that doesn't mean couples are truly monogamous, he said: "A lot of evidence suggests that humans are not monogamous."
Azara's owl monkey is the first primate and only the fifth animal species shown to be perfectly monogamous. The other animals are the California mouse, certain coyotes, the Malagasy giant jumping rat, and Kirk's dik-dik, a small antelope.
Fernandez-Duque and his colleagues collected data on 15 species of mammals that appeared to be monogamous and found that the fathers' investment in their offspring was correlated with promiscuity: The less promiscuity, the more time they devoted to their offspring. The study could not say which came first.
Two studies published last July offered conflicting explanations for the origin of monogamy. One argued that males stuck with their mates to protect their offspring, while the other suggested that males clung to females to protect their breeding rights with their mate. That question remains unresolved.
'A first for primates'
This week's study "is really a first for primates," said Kermyt G. Anderson, an anthropologist at the University of Oklahoma who is co-author of a book on fathers called "Fatherhood." He said there is "surprisingly little data" on monogamy in primates, the classification that includes monkeys, apes and humans.
The link between monogamy and fathers' care for their children fits evolutionary theory, he said. "Males should invest in their offspring only if it's likely to be their offspring," he said.
Studies of monogamy and paternal care in human societies are complicated by the enormous variation in human societies, Fernandez-Duque said. Some communities, such as the Aka pygmies of Central Africa, are marked by strong parental care and close relationships, he said. "In those societies, men and women tend to spend a lot of time together," he said.
In addition to Fernandez-Duque, the authors of "Correlates of Genetic Monogamy in Socially Monogamous Mammals: Insights From Azara's Owl Monkeys" include Maren Huck, Paul Babb and Theodore Schurr.