Stress Relief for Lab Mice: It's Not About the Treadmill

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Take heart, laboratory mice: Purdue University scientists have found that mice raised in cages can relieve stress the same way mice do in the wild.

"The perception of its ability to control stress has a bigger impact on the animal than does the stress itself," said Joseph Garner, assistant professor of animal sciences, in a press release announcing the findings. "Chronic, uncontrollable stress changes animals, making them different than normal. This ultimately makes them less valid research subjects."

In the study, published online in the journal Applied Animal Behavior Science, Garner and his team "asked" mice to "vote with their feet" on which room temperatures they liked best. The scientists placed mouse cages in custom-built baths filled with different temperatures of water, and then connected the cages with tunnels. The mice ran to the cage they wanted to spend time in: The most popular choice was the warmest cage, at 86 degrees Fahrenheit.

Garner and his research team then conducted a second experiment to determine whether mice would build better nests if given the opportunity. Although a normal behavior for wild mice, nest-building is rarely observed in lab mice. So the researchers provided the animals with materials like those found in nature, and the caged mice instinctively built elaborate and complex nests just like those constructed by their wild counterparts

"Nest building is part of the ‘mouseness of mouse,' meaning it is associated with normal mouse behavior and helps define the species' unique characteristics," Garner said.

Nests are a form of protection for lab mice, the research team suggests, allowing them to hide from external threats like light and humans. Garner contends that by allowing lab animals to perform behaviors that reduce stress, they become more reliable research models.

"Ultimately, we want to know whether it could be beneficial for scientists to encourage behaviors such as nest building so that mice are less stressed, healthier, less anxious and more successful in their breeding," Garner said.