Who Knew? Chicks Play Just Like Kittens And Puppies

by techlowdown · 29 August 2022

Young animals explore and learn about the world through play, but many people are surprised to learn that young birds — yes, even domestic chickens — devote a lot of time playing, just like puppies and kittens

“I did not become a vegetarian for my health, I did it for the health of the chickens.”

— Isaac Bashevis Singer (1903 — 1991)

People are familiar with play behaviors in puppies and kittens, but these same people, who typically are not familiar with birds, are often surprised to learn that young birds also play.

Play behavior appears to be ubiquitous in most young animals, and is a way for them to explore and to learn about the world. Further, play behavior is typically characterized by positive emotions, so for these reasons, playfulness can serve as an indicator of positive welfare states in animals.

But reliably identifying play behavior and distinguishing it from non-playful behavior can be quite difficult in some animals, and especially in birds. And far-and-away the most common bird on the planet is the domestic chicken. Which raises the questions: what effects does domestication have on playful behavior in chicks, and what effects do early stressful experiences have on chick playfulness?

In general, domestication of a species is associated with a range of changes in appearance, physiology and behavior, commonly known as the domestication syndrome (ref). These changes include reduced fearfulness towards humans, reduced susceptibility to stress and increased sociability and playfulness. But the genetics underlying behavior are poorly understood.

“Chickens are excellent models for [these studies], since its ancestor, the Red Junglefowl, can be kept in captivity and will breed readily with the domestic variants”, said the senior author of the study, ethologist Per Jensen, a professor in the Department of Physics, Chemistry and Biology at Linköping University. Professor Jensen is an expert in animal behavior (ethology) who specializes in studying the domestication process, animal welfare and behavioral genetics. He also coordinates the AVIAN Behavior Genomics and Physiology group within this department.

“Furthermore, being the most common food producing animal in the world, anything we find out about the behaviour and needs of chickens can be used to improve their welfare on farms”, Professor Jensen told me in email.

Professor Jensen and his team started by comparing play behavior of domestic chicks with that of their wild progenitors, red junglefowl. They didn’t expect to see any qualitative differences in the chicks’ play behavior, but they proposed that they may possibly see increased playfulness in domesticated chickens. To test this prediction, Professor Jensen and his team provided 10 groups of 4 chicks with access to specially designed ‘playgrounds’ for 30 minutes at a time and filmed their behavior. They also provided 10 groups of 4 red junglefowl chicks access to these playgrounds and filmed them.

“We studied the development of young chickens from hatching onwards, by offering them a special ‘playground’ several times a week”, Professor Jensen explained.

In subsequent video analyses, Professor Jensen and his collaborators identified 14 different types of play in the study chicks including picking up objects in their beaks and chasing each other around, and “play fighting” by jumping and bumping their chests against one another.

As predicted, both domestic chicks and red junglefowl chicks showed the same play behaviors. Additionally, Professor Jensen and his collaborators found that the intensity of playful behavior peaked in both domesticated chicks and in red junglefowl chicks between between 25 and 40 days of age — just before the young birds become independent from their mothers. The researchers also found play behavior gradually decreased in birds older than six or seven weeks.

To identify how play changes between wild life and domestic life, Professor Jensen and his collaborators once again compared playful behaviors between domesticated chicks and red junglefowl chicks. The researchers found that play behaviors were identical in domesticated chicks and red junglefowl, and were dominated by object play, despite almost 10,000 years of domestication. However, they found that domestic chicks were more playful than their wild junglefowl ancestors. This observation supports the previous studies that the domestication process leads to animals becoming more childlike in behavior.

Previous studies have found that playing is affected by a young animal’s state of mind, and early stress reduces playfulness. So Professor Jensen and his collaborators proposed they would see similar effects in domestic chicks. But contrary to what they expected, Professor Jensen and his collaborators found that stressed-out domestic chicks play more than their unstressed counterparts.

This surprising result concurs with a previous study that broiler chicks raised in playpens full of toys played less than those in a more barren environment (ref). But why? Were the chicks upset by being physically moved from their home enclosures to the play arena? Was their early exposure in the first few days of life to a high level of stress in a commercial hatchery somehow ‘immunizing’ so the chicks ended up being more tolerant to later stress? This has been reported before in domestic chickens (ref). Or maybe play behavior is not affected by stress and mood in chicks as it is in kittens and puppies? If so, this would suggest that play behavior would not be a useful indicator of chick welfare.

Conversely, is it possible that stressed-out domestic chicks’ welfare can be improved by stimulating play during their first few weeks of life? Maybe.

“We’re planning a study in which we will stimulate stressed animals into playing, in order to increase their wellbeing”, Professor Jensen said. “This could be a way of improving the quality of life of animals used in food production.”

Source:

Gabrielle Lundén, Rebecca Oscarsson, Louise Hedlund, Johanna Gjøen & Per Jensen (2022). Play ontogeny in young chickens is affected by domestication and early stress, Scientific Reports 12:13576 | doi:10.1038/s41598-022-17617-x

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