Sure pigs play. But what does it mean?

“They spin around, twirl, and take a big leap in the air … ,” says Ruth Newberry. “They zigzag a bit … jump up and down, and then flop.”

A dramatic new figure skating routine? No. Newberry is an animal scientist at Washington State University commenting on the behavior that she and colleagues observed in a study designed to learn the effects that early play experience has on the behavior of piglets after they are weaned from their mothers. In broader context, the study is part of a worldwide effort to figure out the function of play in mammals.

One hypothesis, says Newberry, is that play may provide training for unexpected events that may cause stress. For piglets, play experience during the suckling period may help them adapt better to weaning and other stressful situations they encounter growing up.

Weaning is especially stressful for young piglets. Not only are they removed from their mothers, they also experience a dietary switch from milk to solid food and are also introduced to strangers from other litters.

“Piglets are likely to fight at this age,” Newberry said.

The stress of weaning typically depresses play, and Newberry hypothesizes the coping ability in piglets gained from early play experience would be reflected by a more rapid increase in play levels within a few weeks after weaning, compared to their counterparts who had not had that experience.

In fact, Newberry’s results suggest that the more play experience piglets get during their first three weeks of age, especially play with pigs from different litters, the better they cope with the stress of being removed from their mothers during weaning. They also resolve conflicts more rapidly with strangers after weaning.

“It’s tricky, but it’s fun … trying to figure out what really is play,” says Newberry. “Everything they do looks like play, so the hard part is figuring out their intent.”

Domestic pigs are highly social and relatively intelligent mammals that are especially playful at two to six weeks of age, she says. For example, they flop down, use exaggerated movements, kick their legs to one side, bump into one another, and throw each other off balance.

To quantify their playful behavior, Newberry classified the piglets’ various play patterns and took videos of them with different colored dots on their backs. The camera recorded the movement of the pigs and the certain typical play patterns they displayed. Then, using a computer program to track the changes in locations of the colored dots as the piglets played, they analyzed the videos to find out how often each play pattern was performed by the piglets in the different study groups.

“We can learn a lot about their social dynamics through this automated tracking,” Newberry says.

“Play is a sensitive indicator of animal well-being. Finding simple ways of increasing play behavior can mean an increase in health and productivity.”