Search

For over a century, the evolution of animal play has sparked scientific curiosity. The prevalence of social play in juvenile mammals suggests that play is a beneficial behavior, potentially contributing to individual fitness. Yet evidence from wild animals supporting the long-hypothesized link between juvenile social play, adult behavior, and fitness remains limited. In Western Australia, adult male bottlenose dolphins ( Tursiops aduncus ) form multilevel alliances that are crucial for their reproductive success. A key adult mating behavior involves allied males using joint action to herd individual females. Juveniles of both sexes invest significant time in play that resembles adult herding-taking turns in mature male (actor) and female (receiver) roles. Using a 32-y dataset of individual-level association patterns, paternity success, and behavioral observations, we show that juvenile males with stronger social bonds are significantly more likely to engage in joint action when play-herding in actor roles. Juvenile males also monopolized the actor role and produced an adult male herding vocalization ("pops") when playing with females. Notably, males who spent more time playing in the actor role as juveniles achieved more paternities as adults. These findings not only reveal that play behavior provides male dolphins with mating skill practice years before they sexually mature but also demonstrate in a wild animal population that juvenile social play predicts adult reproductive success., Competing Interests: Competing interests statement:The authors declare no competing interest.

Investigations into cooperative partner choice should consider both potential and realised partners, allowing for the comparison of traits across all those available. Male bottlenose dolphins form persisting multi-level alliances. Second-order alliances of 4-14 males are the core social unit, within which 2-3 males form first-order alliances to sequester females during consortships. We compared social bond strength, relatedness and age similarity of potential and realised partners of individual males in two age periods: (i) adolescence, when second-order alliances are formed from all available associates, and (ii) adulthood, when first-order allies are selected from within second-order alliances. Social bond strength during adolescence predicted second-order alliance membership in adulthood. Moreover, males preferred same-aged or older males as second-order allies. Within second-order alliances, non-mating season social bond strength predicted first-order partner preferences during mating season consortships. Relatedness did not influence partner choice on either alliance level. There is thus a striking resemblance between male dolphins, chimpanzees and humans, where closely bonded non-relatives engage in higher-level, polyadic cooperative acts. To that end, our study extends the scope of taxa in which social bonds rather than kinship explain cooperation, providing the first evidence that such traits might have evolved independently in marine and terrestrial realms.

Background: Reported risk factors for the development of a psychogenic movement disorder (PMD) include young age, female gender, history of abuse, current or past psychiatric disorder, lower levels of education and socioeconomic status, and employment as a healthcare worker. Although employment in healthcare is included in several diagnostic criteria for PMD, as well as in many case series, this association has never been validated., Methods: Using the University of Maryland Movement Disorder Database (UMMDD), we identified PMD cases, as well as patients with isolated focal dystonia as controls. An experienced movement disorder specialist diagnosed all patients, and all cases met criteria for clinically established PMD. Demographic and occupational histories were obtained from medical records and were supplemented by telephone interviews. PMD cases and controls were compared using t tests/χ 2 tests., Results: Controls (n = 148) were older than PMD cases (n = 132), with an average age of 61.4 and 52.1 years, respectively ( P  <   0.001); there were no significant differences between groups with respect to gender, education level, and ethnicity. The proportion of healthcare workers was not significantly different between PMD cases and controls (25% of PMD cases vs. 20% of controls; P  =   0.28)., Conclusions: In contrast to traditional teaching, this investigation demonstrates that in our patient population, patients with a PMD were no more likely to be employed as healthcare workers than patients with isolated focal dystonia. This study calls into question the use of employment in healthcare as a reliable criterion to support the diagnosis of PMD.