The differences in the frequency of play by chicks can be explained by sex differences in behaviour of adults.
Scientists have being observing the frequency of play by aged chicks between six and 53 days old. The examination showed that males engaged more frequently in social and object play than females.
The scientists observed the chicks for 30 minutes in these playpens and scored the occurrence within 15-second intervals of play by each chick. The chicks were observed on 15 different days, when they were between six and 53 days old.
The researchers distinguished 12 distinct play behaviours. Examples of locomotor play were frolicking and wing flapping. Object play included chasing an object or pecking at it or exchanging it with another chick. Social play included sparring, jumping, and sparring stand-offs.
Object play was more frequently seen than social play, while locomotor play was least common. Both females and males showed every type of playful behaviour.
However, the frequency of play differed between them: male chicks played more overall than females. This was due to males engaging more often in object and social play, while there was no difference between the sexes in the frequency of locomotor play.
The researchers concluded that these patterns can be explained by the strong sexual dimorphism of adult red junglefowl, who are the ancestors of domestic chickens. Red junglefowl display a pronounced difference between the sexes in morphology, coloration, and behaviour.
This difference means that male chicks benefit more from practicing skills related to physical ability and social tactics.
Play is widespread across the animal kingdom. Yet what is its function? One hypothesis is that play is beneficial to individuals because it allows them to practice skills needed later in life.
Red junglefowl were domesticated by humans between 7,000 and 8,000 years ago in mainland Southeast Asia. In all junglefowl species, males are more colourful, aggressive, and vigilant than females, and provide food for their mates.
Many questions remain unanswered with respect to the adaptive functions of play, for example its effects on later cognitive abilities.
The research appears in the journal Frontiers in Ethology, titled “Male chicks play more than females – sex differences in chicken play ontogeny.”
