What A Week Of Freedom Can Do For A Lab Mouse

Each time Matthew Zipple, a behavioral ecologist at Cornell University, releases a mouse that was born and raised in a laboratory into the green expanse of a field, he is amazed. He transports the mouse in a paper cup, lays the cup on its side in the grass, and takes off the lid. "When the lids come off it’s like they are on another world, from their perspective," he wrote in an email. "There are a million new smells, there’s grass, there’s dirt, there is sunshine."

The mouse's new world is an enclosed field approximately 10,000 times the size of their shoebox-sized cage. The field is full of other former laboratory mice, each of whom lived the same shoebox life before the field. Within a few days, the mouse has explored the entire enclosure. "They are doing things that they couldn’t do in the lab and that their ancestors haven’t done for dozens of generations—things like bounding over grass and digging in the dirt," Zipple said. In the field, the mice build nests, dig burrows, and find their own food. They choose which mice to socialize with, and when. For the first time in their lives, they experience weather.