Cooperation Helps Monkeys Too

Here, a lesser male sits with an offspring that he may not have been to produce without joining and helping an alpha male out. (Photo : Noah Snyder-Mackler)

The old axiom that teamwork and cooperation breeds more success than going at it alone is evident in our human society. It seems that our cousins on the evolutionary tree have taken notice, and are taking notice. Turns out that alpha male gelada monkeys who allow subordinates into their group rather than beating them back have longer tenures as top dog and breed on average three more offspring during their lifetime.

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Cooperation between animals is not uncommon, and many interesting bonds take place in nature.

"For example, in some species unrelated males will sometimes tolerate the presence of one another and, in rare cases, form bonds and even appear to cooperate," said research leader Noah Snyder-Mackler.

"These findings demonstrate a benefit of forming multi-male groups in a predominantly single-male system, an important step in the evolution of sociality among unrelated competitors," Bergman said.

But why would an alpha male with a cast of females at his disposal to mate with allow other males to intrude on his chances of passing on his genes? The answer is quite simple: defensive purposes.

By allowing lesser males into his group, an alpha male gelada can expect them to help protect the group and the alpha male from other intruding males. There is less pressure on the alpha male to be the only line of defense, and there is always strength in numbers.

An intriguing observation from the study shows that subordinate males who were allowed to mate stuck around the group longer.

"This suggests," Thore Bergman, an assistant professor of psychology at Michigan with whom Snyder-Mackler collaborated with on the study. "That the alpha males may allow the subordinate to reproduce as a 'staying incentive' for defending the group, a payment for their services."

The research does not conclude that this behavior is completely kosher with the alpha male, and it is possible that lesser males may simply be stealing chances to mate when they can.