In 1972, animal behaviorist John Calhoun built a mouse paradise with beautiful buildings and limitless food. He introduced eight mice to the population. Two years later, the mice had created their own apocalypse. Here’s why.
Universe 25 was a giant box designed to be a rodent utopia. The trouble was, this utopia did not have a benevolent creator. John B. Calhoun had designed quite a few mouse environments before he got to the 25th one, and didn’t expect to be watching a happy story. Divided into “main squares” and then subdivided into levels, with ramps going up to “apartments,” the place looked great, and was always kept stocked with food, but its inhabitants were doomed from the get-go.
Universe 25 started out with eight mice, four males and four females. By day 560, the mouse population reached 2,200, and then steadily declined back down to unrecoverable extinction. At the peak population, most mice spent every living second in the company of hundreds of other mice. They gathered in the main squares, waiting to be fed and occasionally attacking each other. Few females carried pregnancies to term, and the ones that did seemed to simply forget about their babies. They’d move half their litter away from danger and forget the rest. Sometimes they’d drop and abandon a baby while they were carrying it.
The few secluded spaces housed a population Calhoun called, “the beautiful ones.” Generally guarded by one male, the females—- and few males — inside the space didn’t breed or fight or do anything but eat and groom and sleep. When the population started declining the beautiful ones were spared from violence and death, but had completely lost touch with social behaviors, including having sex or caring for their young.
This blew my mind.
On another note, I spent a week away in Croatia and Bosnia of all places. I highly recommend it.