The Social Network: Why mama chimps behave differently with sons and daughters

Ah, social skills. The curse of awkward teenagers everywhere and a key factor in determining the success of your upcoming blind date. As humans, we use our social skills to communicate and interact with others in both selfish and altruistic ways.

Like humans, chimps are highly social animals that live in communities. (Source)
Like humans, chimps are highly social animals that live in communities. (Source)

Chimpanzees, our closest living relative, also possess deft social skills. Adult male chimpanzees rely heavily on their social skills to form coalitions with other males to help them rise in the ranks and produce more offspring. On the other hand, female chimpanzee hierarchies are not determined based on strength and aggression, but rather, based on age. Females also spend a lot of time by themselves, nursing and taking care of their offspring. Are having good social skills, then, more important for male chimps than for female chimps? Would male infant chimps benefit more from having social interactions than females?

These are the types of questions that interest Dr. Carson Murray, a primate behaviour ecologist. Dr. Murray studies the relationship between mothers and infants in chimpanzees and how that relationship can influence the well-being of the offspring and its eventual success as an adult. In a new study published last week, Dr. Murray and her colleagues looked at whether mothers of sons behave more socially than mothers of daughters to help their sons develop better social skills.

Mother chimps play a key role in the development of survival and social skills in their young. (Source)
Mother chimps play a key role in the development of survival and social skills in their young. (Source)

For the last 40 years, researchers at Gombe National Park in Tanzania have been carefully following individual chimpanzees and recording their movements and associations. Like humans, chimpanzees have a dynamic social system. While chimpanzees live in stable communities, these communities often break into smaller subgroups, or parties, that travel, forage or rest together. The make-up of parties changes constantly as old members leave and new members join. Using data collected over a 37-year period, Dr. Murray’s team was able to compare the behaviour of the same mother when she had male and female infants.

The researchers found that mothers with sons spent more time with other chimps than mothers with daughters. In the first six months of infancy, mothers with sons spent on average roughly 55% of their time in parties while mothers with daughters spent on average 40% of their time in parties. Mothers with sons belonged to parties that were larger than those of mothers with daughters. During the first six months, mothers with sons also spent more time in parties with both male and female chimps than mothers with daughters. There was no difference in the amount of time the different mothers spent in female-only parties. This means that from a very early age, male infant chimps are being exposed to a wider social network with more male role models than female infant chimps.

If social skills are so useful, why aren’t mothers equally social with daughters as they are with sons? As it turns out, hanging out with others can also be quite stressful and dangerous. Being in a party increases competition for food and also puts the infant at a higher risk of infanticide by other members of the party. It seems like mothers with sons make a calculated decision to spend more time with others because the potential benefits to their sons outweigh the potential risks of associating with others. By exposing their sons to large social groups and older males early in their life, these mothers are providing opportunities for their sons to observe and learn important social skills. In fact, an earlier study looking at the same population in Gombe found that when mothers more frequently associated with adult males during their sons’ early years, their sons were more likely to achieve a higher rank as adults. In the case of daughters, increased social exposure provides few, if any, advantages down the road so mothers are more likely to avoid the risks of associating with others.

The limited edition Lego Research Institute set featuring female scientists sold out within a day. (Source)
The limited edition Lego Research Institute set featuring female scientists sold out within a day. (Source)

How does this study relate to humans? There is already a growing body of work that focuses on how parents behave differently towards their child based on the child’s gender. For example, researchers looked at how moms intervened in their child’s risky behaviour on a playground. They found that daughters received more cautions and warnings about risk and vulnerability for injury while sons received more statements encouraging risk-taking behaviour. Now, more than ever, there is increased awareness and concern about gender stereotypes in children’s toys and movies. As parents fight to put strong female role models in Disney movies and pink tool kits on store shelves, it’s important to keep in mind that our words and actions may, themselves, be inherently gender-biased.

References:

Murray, C.M., Lonsdor, E.V., Stanton, M.A., Wellens, K.R., Miller, J.A., Goodall, J., and Pusey, A.E. (2014) Early social exposure in wild chimpanzees: Mothers with sons are more gregarious than mothers with daughters. Proceedings of the National Academy of Sciences, 111: 18189-18194.

Morrongiello, B.A., and Dawber T. (2000) Mothers’ responses to sons and daughters engaging in injury-risk behaviors on a playground: implications for sex differences in injury rates. Journal of Experimental Child Psychology, 76: 89-103.

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