Even though female mountain gorillas remain a member of the group into which they were born, and regardless of the odds that their fathers are the alpha male of those groups, inbreeding amongst members of the species is rare, according to a new study.
Writing in the latest edition of the journal Behavioral Ecology and Sociobiology, Max Planck Institute for Anthropology researcher Linda Vigilant and her colleagues explain that the female mountain gorillas have developed a strategy designed to avoid mating with their fathers.
These tactics are so effective that the odds of a father-daughter mating pair amongst members of the species is essentially zero, the authors explained in a statement. While a dominant male often remains in charge of his group as his daughters sexually mature, the researchers report that 60 percent of females typically move on to another group, away from their fathers.
Age preferences may explain the lack of inbreeding
Vigilant and her fellow investigators performed genetic testing on fecal samples to establish the paternity of 97 mountain gorillas, and found that on average, 72 percent of offspring were part of a group with more than one male present. However, not one of them was found to be the father of one of his daughter’s offspring.
“The probability of a dominant male siring his daughter’s offspring is effectively zero, while on average he has almost two-to-one odds of siring any other offspring,” Vigilant said. Some forms of inbreeding were discovered, however, as nine out of 79 gorillas living amongst four groups of gorillas that have been monitored since 1967 were found to be at least half-siblings.
Even though adult male gorillas are so much larger than female ones, it is the females that make choices pertaining to mates and initiate most of the reproductive behavior. The discovery that more than one subordinate male can father offspring in a group appears to indicate that female gorillas have different preferences when it comes to selecting a mate.
So how do fathers and daughters know how to avoid copulating with one another? Vigilant and her colleagues found that the daughters of dominant males seek out subordinate males which are far younger than their fathers, which could suggest that they use relative age to avoid inbreeding with their fathers. Furthermore, the results suggests that dominant males may prefer mating with older females who are already experienced mothers, the authors added.