Researchers have confirmed that donkeys have far more subtle ways of expressing pain than horses. | Photo: iStock

“They’re much harder to read in terms of pain behavior than horses; they have a different set of behaviors that relate to their pain experience,” said Rebecca Whay, PhD, of the University of Bristol School of Veterinary Sciences, in the U.K. “They’re speaking their language through behavior. (They’re) working equids who … have an awful lot of problems but seem so calm. But when you learn to watch their behavior it’s like watching them shouting.”

Whay and her fellow researchers studied 40 male cart-pulling donkeys in Pakistan that had been identified by a charitable organization as having health issues, including poor body condition, poor hoof condition, wounds, and lameness. They treated half the donkeys with a pain-killer (meloxicam) and the other half with a placebo as a control group. Then they observed the donkeys’ behavior at rest for the next four hours.

They found that the treatment group was more alert and interested in the environment and exhibited more investigative behavior than the control group, Whay said. They also yawned and licked more and lay down less often than controls. Meanwhile, donkeys in the control group shifted their weight and kept their eyes closed more often