Scientists have discovered that female bonobos band together to protect against male harassment. Older females will help unrelated younger females, a behavior not usually seen in other primates. The findings are in a study just published in the journal Animal Behaviour.
In some primate species, females will help protect each other. Generally, this occurs in species where females stay with their family while males leave after reaching sexual maturity. Since the females are all related, it makes sense for them to help each other. Bonobos, however, are male-philopatric, meaning the males are the ones that stay in the group while females leave their birth family. Female bonobos in a group are unrelated so it puzzled scientists to observe them forming coalitions to attack males.
Male bonobos will sometimes harass and attack younger females. Older females, even ones not friendly with the female being harassed, will help drive off the aggressive males. All of the females in the group will often form alliances, regardless of relatedness or friendships. The researchers noted that they always won against the males when they banded together in this way, reducing overall aggression in the group.
The authors speculate that bonobo females evolved this behavior in order to protect against male aggression. By working together, everyone benefits and new females can safely join the group. The researchers also believe these partnerships may benefit the older females in another way. If younger females begin spending a lot of time with the older females to stay safe, they might mate with the older females’ sons in the future.
Forming coalitions allows female bonobos to combat male aggression, helping them stay safe and in charge. In bonobo societies, older females are at the top of the social hierarchy. These older females benefit from helping younger females because it’ll provide future mating opportunities for their sons. The authors also speculate that these behaviors help foster friendships, increasing tolerance in the group.
Nahoko Tokuyama and Takeshi Furuichi. Do friends help each other? Patterns of female coalition formation in wild bonobos at Wamba. Animal Behaviour (2016).