London, Jan 12 (ANI): A new study has shown that alpha-male chacma baboons allow lower-ranking males to mate with their females as a way to protect the dominant male's own offspring in their absence.
Louise Barrett of the University of Lethbridge in Alberta, Canada, and colleagues reached at this conclusion by studying 11 years of observations from a baboon troop in De Hoop Nature Reserve, South Africa, reports New Scientist.
Chacma baboons have a despotic social structure in which a single alpha male can almost completely monopolise mating opportunities by guarding females during their oestrus periods.
Yet Barrett found that subordinate males in the De Hoop troop fathered 23 of 64 offspring during that time.
Closer analysis showed that this was not because the alpha male was too tired, too busy, or too inexperienced to guard the females.
Instead, he appeared to be willingly ceding copulations to subordinate males.
The alpha male's apparent generosity may be a strategy for protecting his young after he is no longer around.
When an alpha male dies or wanders off, new alpha males - usually from an outside group - move in, and tend to try to kill infants from the previous regime.
Barrett said that having 'spare dads' in the troop helps ensure that these infants receive protection.
Sure enough, subordinate males who had fathered an offspring were more likely to stick with the troop - an average of 23 months, versus just five months for subordinates without offspring.
This may allow them to form closer social bonds with the females, which makes them more likely to protect females and infants.
The study appears in Proceedings of the National Academy of Sciences. (ANI)