The "Universe 25" social experiment merits a mention here.
In 1968 John Calhoun created a veritable paradise for mice. 4 mouse couples were introduced into a special environment, where all their needs, including unlimited food and drink and abundant nesting materials were within easy reach (no more than 15 seconds away). The lighting and temperature were maintained at a perfect level and obviously no cats or other predators were permitted to intrude on this mousey heaven.
The only limited resource in this microcosm was physical space, and Calhoun suspected that it was only a matter of time before this caused trouble in paradise.
As Calhoun had anticipated, the utopia became hellish within a year as the population density began to peak. Then population growth abruptly and dramatically slowed. Animals became increasingly violent, developed abnormal sexual behaviors and began neglecting or even attacking their own pups. Calhoun termed this breakdown of social order a “behavioral sink.”
Eventually Universe 25 took another disturbing turn. Mice born into the chaos couldn’t form normal social bonds or engage in complex social behaviors such as courtship, mating, and pup-rearing. Instead of interacting with their peers, males compulsively groomed themselves; females stopped getting pregnant. Effectively, says Ramsden, they became “trapped in an infantile state of early development,” even when removed from Universe 25 and introduced to “normal” mice. Ultimately, the colony died out. “There’s no recovery, and that’s what was so shocking" Calhoun says.
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