Joseph Garner’s work easing life for laboratory mice took a turn in 2004 with an incidental observation at a scientific talk. The speaker — a colleague and future collaborator — presented a graph showing that mice, who prefer balmy climes in the upper 80s, experienced increased metabolic rates in cooler laboratory temperatures.
Photograph by BRIANNA GASKILL
“What was so striking about the graph,” recalls Garner, PhD, an associate professor of comparative medicine who’s studied animal welfare for more nearly two decades, “was how stressed the mice would be by the temperatures we normally house them at.”
He began to think that the chilly temperatures, mandated by federal rules, could help explain why one out of 10 drugs successfully tested in mice end up not working in people.
“If you want to design a drug that will help a patient in the hospital, you cannot reasonably do that in animals that are cold-stressed and are compensating with an elevated metabolic rate,” he says. “This will change all aspects of their physiology — such as how fast the liver breaks down a drug — which can’t help but increase the chance that a drug will behave differently in mice and in humans.”
Garner is among a handful of researchers studying the issue and advocating for mice, hundreds of millions of which live in research labs. The work already has led to changes in animal care regulations and spurred more interest in the psychological, as well as physical, well-being of the animals, he says.
Garner is a great admirer of mice, who are among the planet’s most flexible of creatures, able to live alongside humans in even the most uninhabitable places.
“Our shared history makes them the perfect research animal,” he says.
Laboratory mice are kept in the cold because it suppresses their aggressive tendencies. Raising the temperature would make them unmanageable.
So Garner and his colleagues found a simple solution. In a recent study, they observed that if mice are supplied with shredded paper, they will build a cozy nest that allows them to naturally regulate their temperatures to a comfortable level.
The mice could move between cages of varying temperatures and with varying amounts of nesting material, telling the researchers how nesting material compensates for cold temperatures. The animals routinely chose a warmer locale, though some of them wanted to have it all — a warm spot and a nice little home, too.
“They would go on holiday somewhere AND take their nest with them,” Garner says. “Some people like to take a pillow on holiday and some don’t. These mice were packing their own pillow.”
He says nests also help decrease the animals’ stress and anxiety.
“The really obvious explanation is that they can hide in it — hide from us, because we are their predators. Imagine you are hiding from a Tyrannosaurus rex — you want a couch to hide under. That is a little like what’s going on,” he says.
He says mouse nests can help researchers in other ways as well. “The shape of the nest tells an experienced person whether the animals are too hot or too cold, whether they are sick or whether they are about to give birth,” Garner says. “Once you learn how to ‘speak mouse nest,’ the nest is a wonderful tool that anyone can use to assess the general state of the mouse.”
— Ruthann Richter