A new study reports gelada baboons are as tactically deceptive as people when it comes to trying to cover their sexual indiscretions with another from their mate. No, they’re not covertly deleting their text or email messages. Nor are baboons anxiously explaining why they’re frequently working later than usual, using the time to have an illicit rendezvous.
Aliza le Roux, a behavioral ecologist at the University of the Free State in South Africa indicates there are evolutionary roots to hiding sexual infidelity. However, it’s rare to see it revealed outside of human society.
Le Roux and her colleagues ventured to the Simien Mountains National Park in Ethiopia and observed the hierarchies and social behaviors of gelada baboons. From January 2009 to December 2011 researchers documented activity amongst 19 reproductive units.
A gelada can typically live to around 20 years old. The most basic groups of geladas are reproductive units made up of one to 12 females, their young, and one to four males. There are also all-male units made up of two to 15 males. Herds consist of up to 60 reproductive units, sometimes from different bands. Communities are made of one to four bands whose home ranges overlap.
Gelada baboons (Theropithecus gelada) cohabitate in social units composed of several females and a dominant alpha male. This “top dog” has exclusive rights to the females. However, subordinate males manage to sire an average of 17 percent of the offspring. Analysts recorded 939 in-unit copulations between a dominant male and one of his females and 93 external-unit copulations where intercourse occurred between a subordinate male and a female.
Geladas only reside in the high grassland of the deep gorges of the central Ethiopian plateau. It would be assumed a dominant male would detect and inhibit infidelity from occurring. But researchers found cheating happened when the alpha male was at least 65 feet away. Instead of producing typical loud mating calls, cheating geladas attempted to conceal the torrid affair by remaining abnormally quiet. The study team considered these behaviors as tactically deceptive and not solely opportunistic.
It was also found that alpha males in the units inflicted punishments on those caught cheating, rushing at the pair and trying to bite them, along with other demonstrations of aggression. This reaction did little to deter the infidelity long-term as the cheating pair would eventually re-offend.
[Image via Wikipedia]