A few questions about play...

Question: Are certain families more playful than others? If so, do you think that it results more from genetics or rearing and influence of the mother and older siblings?

Great follow up! But oh man, that's a LOT to unpack (in the good way).

My dissertation project investigates the development of sex differences in chimpanzee social strategies with a focus on play to track those diverging strategies. One of the questions that my data will address is whether males are generally are more playful than females, and if so, how early in development does that difference emerge (see footnote 1 for more on sex differences)? We have some good evidence from other sites (like Gombe, Lonsdorf et al. 2014A, Lonsdorf et al. 2014B) that sex differences in the amount of time spent playing and increased number of social partners among males do emerge early in development. That said, yes, some families do seem (and certainly are actually) more playful than others. 

While I haven’t dived directly into “family effects” yet, it seems to me that bigger families with more siblings are more playful. Of course, this might be entirely explained by the fact that having more siblings around means having more play partners around. Additionally, based on those prior findings about young male sociality, It can also be affected by whether or not those family groups are made up of more male versus female siblings. Honestly, I do think that availability has a lot to do with it: as long as there’s someone around to play with, its most likely going to happen. 

Have babies, will play!

Lia also has a long line of kids that play with each other pretty constantly... I feel like together, the impression you really get from this post is that all the infants do is bite feet...

​In my study, since our primary interest focuses on sex differences, we need to quantify maternal and paternal effects in oder to control for them. In other words, we want to make sure that any sex differences we find are really caused by sex and not a consequence of have one mom that has all female offspring, and another has all males and really each family is just more like their mom. However, we should be able to use my dataset to address general maternal experience effects versus “just” genetics contributed by fathers. If those models show that either paternal or maternal identity has a large effect on differences in male and female social behavior, then of course I plan to dive right in and tease them apart! 

Outamba's family is particularly large, particularly playful, and almost entirely female- which is a great example of why we have to be really careful to control for maternal identity in our statistical approaches

First of all, I just want to say that I really love answering readers' questions and talking about the parts of chimpanzee behavior that other people are interested in too! So please, please, PLEASE, keep them coming! I can promise you that, even if it takes me a bit of time, I will get back to you and answer your questions as well and as thoroughly as possible. Every time :) 

Question: Do you think playful adults like Tenkere were playful infants, like Tembo, and that Tembo will continue on as a playful adult? 

To answer your question: yes, in general, I do think that more playful mom’s raise more playful offspring. But it’s a complex problem! I’m going to try to answer you as completely as I can while also trying to keep it brief and not bore people.  ​

Mom's also have different play styles. It might not look like it but Tongo is playing with Tangawizi just by wiggling her toes for him to grab and bite at.

​The amount of time that chimpanzees spend playing either on their own or socially, declines quite a lot with age. This is pretty typical across mammals, and especially primates: infants and juveniles play a lot, then, as they reach reproductive maturity, play becomes much less frequent and by adulthood, playing is quite rare. However, my suspicion is that, “playfulness” as a sort of personality trait remains relatively stable throughout life.

Here, Wangari show us her passive hand play style with Winza.

Additionally, to fully consider playfulness, we have to think about energy availability too. We know that, in general, sociality is limited or constrained by food (aka energy) availability and play is one of the most energetically expensive types of social behavior. However, when food availability starts to decline, playfulness might change quite a lot both between and within individuals. Even among those certain individuals are very playful when food is ample, some individuals might be reduce play more or less than others if there isn’t as much calorie-dense food around. For those reasons, it’s very important to consider relative playfulness in two ways: first, how playful is one individual is compared to others in the same group at the same time after controlling food availability? Second, for each playful individual, how does playfulness change across time and during times of plentiful versus scarce food availability?

The most accurate way for me to word my answer to your question it that I predict, after controlling for typical declines in play with age and current energy availability, that relatively more playful chimps remain relatively more playful. ​ But stay tuned because I will have a more concrete answer coming right up as soon as I can get through these videos!

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Footnotes:​
1In chimpanzees, adult males are generally considered to be more social than females (for details, check out the references at the bottom of this footnote), however, we don’t know if this sex difference is present from birth or emerges at some point during development. As play is the most common social interaction among young chimpanzees, that is one type of behavior that we can focus on to examine sex differences. As I analyze my dissertation data I’ll be trying to answer questions like: are males more playful than females? Do they initiate play more often? Spend more time playing? If so, how early does this sex difference emerge and how do general patterns of playfulness change with age? Do males and females play differently? Do they use different play styles? Focus on different partners? Do they use different play styles in response to the partners that they choose? 

(1) Goodall, J. (1986). The chimpanzees of Gombe: Patterns of behavior. 
(2) Wrangham, R. W. (1980). An ecological model of female-bonded primate groups. Behaviour, 75(3), 262-300.
(3) Wrangham, Richard W. "Why are male chimpanzees more gregarious than mothers? A scramble competition hypothesis." Primate males: causes and consequences of variation in group composition. Cambridge University Press, Cambridge (2000): 248-258.
(4) Otali, E., & Gilchrist, J. S. (2006). Why chimpanzee (Pan troglodytes schweinfurthii) mothers are less gregarious than nonmothers and males: the infant safety hypothesis. Behavioral Ecology and Sociobiology, 59(4), 561-570.
(5) Lehmann, J., & Boesch, C. (2009). Sociality of the dispersing sex: the nature of social bonds in West African female chimpanzees, Pan troglodytes. Animal Behaviour, 77(2), 377-387.