PREVIEW

A study published in the journal Frontiers in Ethology has shown that male baby chickens play significantly more than female chicks.
Researchers on the study concluded that male chicks play more than female chicks after incubating white leghorn chickens on a farm and determining each chick’s sex based on its wing measurements.
Once born, the chicks lived in cages and were taken to larger arenas called ‘playpens’ for half an hour twice per week.
During this play time, researchers scored the occurrence of play by each chick.
The chicks observed in the study were between six and 53 days old.
“Here we show for the first time that there are clear sex differences in the age-related development of play in chickens,” the study’s author Rebecca Oscarsson said in a statement. “This difference is mainly because males engage more in social and object play.”
While observing the baby chickens, researchers distinguished 12 different play behaviours: frolicking, wing flapping, chasing objects, pecking objects, exchanging objects with other chicks, sparring, jumping, sparring stand-offs, worm-running, and others.
The researchers simulated worm-running by introducing a fake rubber worm into the playpen about 10 minutes into play time.
They speculate that this play behaviour marks a precursor to ‘tidbitting’, a courtship behaviour wherein an adult male chicken manipulates food items for the enjoyment of an adult female chicken.
After scouring their data, the researchers concluded that the male chicks played more overall than the female chicks.
In particular, male chicks participated far more in object play – chasing objects, pecking objects, exchanging objects with other chicks – and social play – sparring, jumping, sparring stand-offs.
Male chicks played most when they were 43 days old on average, while female chicks played most when they were 36 days old on average.
“We still don’t know the adaptive function of play for any species,” Linköping University professor Dr Per Jensen added in his own statement. “However, the present study indicates that a possible function is to prepare animals for specific challenges they may encounter later in life. In a species like the chicken, where only males compete for territories, it makes sense that they engage in more social play as young.”
Domestic chickens are directly descended from red jungle fowl, which feature pronounced differences in morphology, colouration, and behaviour between the sexes.
The study’s researchers suggested that chickens inherited their differences in play behaviour from this ancestor, and that they play to prepare for adult life.
Also known by its Latin name Gallus gallus, the red jungle fowl is a tropical bird found across South Asia.
An adult male red jungle fowl can grow up to 28 centimetres (11 inches), and the whole bird may be as long as 70 centimetres (28 inches), while a female red jungle fowl may grow up to three-quarters of this size.
Dr Jensen continued, “Many questions remain unanswered with respect to the adaptive functions of play, for example its effects on later cognitive abilities. We now plan to look into the neurobiological and genetic mechanisms of play.
“For example, it’s possible that the early development of the cerebellum is linked to play behaviour.”