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Abstract Many mammalian species display sex differences in the frequency of play behavior, yet the animal literature includes few longitudinal studies of play, which are important for understanding the developmental timing of sex differences and the evolutionary functions of play. We analyzed social play, solitary play, and grooming using an 18‐year data set on 38 wild white‐faced capuchin monkeys (Cebus capucinus) followed since infancy. Rates of each behavior were measured as the proportion of point samples taken during focal follows in which the individual engaged in each behavior. To determine sex differences in these rates, we ran a series of generalized linear mixed models, considering both linear and quadratic effects of age, and chose the optimal model for each of the three behavioral outcomes based on information criteria. Rates of both social play and solitary play decreased with age, with the exception of social play in males, which increased in the early juvenile period before decreasing. Male and female capuchins had different developmental patterns of social play, with males playing more than females during most of the juvenile period, but they did not display meaningful sex differences in solitary play rates. Additionally, males and females had different patterns of grooming over the lifespan: males participated in grooming at low rates throughout their lives, while adult females participated in grooming at much higher rates, peaking around age 11 years before declining. We suggest that male and female white‐faced capuchins may adopt alternative social bonding strategies, including different developmental timing and different behaviors (social play for males vs. grooming for females). Our results were consistent with two functional hypotheses of play, the practice and bonding hypotheses. This study demonstrates that play behavior may be critical for the development of sex‐specific social strategies and emphasizes the importance of developmental perspectives on social behaviors.
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Genetic Variation in Male Aggression Is Influenced by Genotype of Prior Social Partners in Drosophila melanogaster
Social behaviors can be influenced by the genotypes of interacting individuals through indirect genetic effects (IGEs) and can also display developmental plasticity. We investigated how develop- mental IGEs, which describe the effects of a prior social partner’s geno- type on later behavior, can influence aggression in male Drosophila melanogaster. We predicted that developmental IGEs cannot be esti- mated by simply extending the effects of contextual IGEs over time and instead have their own unique effects on behavior. On day 1 of the ex- periment, we measured aggressive behavior in 15 genotypic pairings (n p 600 males). On day 2, each of the males was paired with a new opponent, and aggressive behavior was again measured. We found con- textual IGEs on day 1 of the experiment and developmental IGEs on day 2 of the experiment: the influence of the day 1 partner’s genotype on the focal individual’s day 2 behavior depended on the genotypic iden- tity of both the day 1 partner and the focal male. Importantly, the devel- opmental IGEs in our system produced fundamentally different dynam- ics than the contextual IGEs, as the presence of IGEs was altered over time. These findings represent some of the first empirical evidence dem- onstrating developmental IGEs, a first step toward incorporating de- velopmental IGEs into our understanding of behavioral evolution.
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- Award ID(s):
- 1856577
- PAR ID:
- 10498729
- Publisher / Repository:
- The American Naturalist
- Date Published:
- Journal Name:
- The American Naturalist
- ISSN:
- 0003-0147
- Page Range / eLocation ID:
- 000 to 000
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1086/729463
