by MARIS FESSENDEN
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John Calhoun studied behavior during overcrowding in mice and rats
What does utopia look like for mice? According to a researcher who did most of his work in the 1950s through1970s, it might include limitless food (of course!), multiple levels and secluded little rodent condos. These were all part of John Calhoun’s experiments to study the effects of population density on behavior. But what looked like rat utopias and mouse paradises at first quickly spiraled into out-of-control overcrowding, eventual population collapse and seemingly sinister behavior patterns.
The mice were not nice.
For io9, Esther Inglis-Arkell writes about Calhoun’s twenty-fifth habitat and the experiment that followed:
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.
Calhoun’s experiments, which started with rats an outdoor pen and moved on to mice at the National Institute of Mental Health during the early 1960s, were interpreted at the time as evidence of what could happen in an overpopulated world. The unusual behaviors he observed he dubbed “behavioral sinks.”
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