In the words of one of Calhoun’s collaborators, rodent “utopia’ had descended into ‘hell.’” Even when reintroduced to normal rodent communities, these ‘socially autistic’ animals remained isolated until death. At the experiments’ end, the only animals still alive had survived at an immense psychological cost: asexual and utterly withdrawn, they clustered in a vacant huddled mass. Calhoun called this vortex “a behavioral sink.” Their numbers fell into terminal decline and the population tailed off to extinction. Males became hypersexual, pansexual and, an increasing proportion, homosexual. Violence quickly spiraled out of control. “In the sealed enclosure, flight was impossible. What went wrong?Īccording to Calhoun, the death phase consisted of two stages: the “first death”-characterized by the loss of purpose in life beyond mere existence (including the loss of desire to mate, raise young, or establish a role within society)-and “second death” marked by the literal end of life and the extinction of Universe 25.Īccording to a researcher and reviewer of Calhoun’s experiments, Edmund Ramsden, author of “The urban animal: population density and social pathology in rodents and humans,” stated: The Utopia was designed to hold more than 3800 mice, but at 2200 their society began to decay. In each experiment: Early on the mice, with no need to forage or build (no work), would initially breed in large quantities soon a leveling-off occurred then, the mice would develop either aberrant, hostile or anti-social behaviors finally, the population would die off to extinction. From 1954 to 1972, working with the National Institute of Mental Health (NIMH), Calhoun spent years trying to perfect his experiment with continual redesigns of his rodent cities, Universe 25, repeating it 25 times (thus the title Universe 25). The mice were specifically chosen because they were healthy and disease was blocked from entering the Utopian city, and there were no predators. He gave them unlimited food and water, nest areas and nesting material, perfect climate control. Calhoun, sought to answer this question.Ĭalhoun started with just four pairs of breeding mice and put them in the Utopian “city” he created. What happens to society if all our appetites are catered to, with all of our needs and wants met? One ecologist and psychologist, John B. (2013).Living the Human “Universe 25” Experiment Nuclear Gene Variation in Wild Brown Rats. W., Zhang, Y.-H., Cong, L., Wang, Y., Zhang, J.-X., & Keightley, P. There were no black rats, mole rats, or any other kinds of rat used. Therefore, apart from the fact that the article was discussing data on a domesticated albino strain of the Norway rat, all the experiments mentioned used brown rats. 2012), no matter where in the world you collect them (Ness, 2013). There is very little genetic variation in brown rats (Ness, et al. In each case my associates and I maintained close surveillance of the colonies for 16 months in order to obtain detailed records of the modifications of behavior induced by population density. Each was permitted to increase to approximately twice the number that my experience had indicated could occupy the available space with only moderate stress from social interaction. The data for the present discussion come from the histories of six different populations. Then he turned to a domesticated albino strain of the Norway rat under more controlled circumstances indoors, and Even with only 150 adults in the enclosure, stress from social interaction led to such disruption of maternal behavior that few young survived. The reason this larger population did not materialize was that infant mortality was extremely high. Yet adult mortality was so low that 5,000 adults might have been expected from the observed reproductive rate. By the end of 27 months the population had become stabilized at 150 adults. There could be no escape from the behavioral consequences of rising population density. 'With an abundance of food and places to live and with predation and disease eliminated or minimized, only the animals' behavior with respect to one another remained as a factor that might affect the increase in their number. I confined a population of wild Norway rats in a quarter-acre enclosure. Reading the article you mentioned, Calhoun (1962) started with wild Norway Rats, also referred to as common rats, brown rats, street rats, sewer rats, or Hanover rats. No, Calhoon did not account for genetic diversity in his experiments outlined in your question.
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