They simply stopped reproducing and destroyed themselves. What killed them off was their own behavior. The rat and mice populations died out not because of lack of resources or lack of space or because of diseases, etc. Eventually breeding activity stopped and the population declined to the point of total extinction.Ĭalhoun's original intention was to study the effects of overpopulation, and of course most of the people who cite his experiments do so in terms of overpopulation, however overpopulation is not exactly what happened in Calhoun's experiments.
Calhoun describes many of the mice spending their time grooming themselves and doing other solitary behaviors, which he called "the beautiful ones". Females stopped caring for the young, males didn't need to defend their resources because of the lack of scarcity but did form into groups that attacked each other, cannibalism, and Calhoun specifically mentions an increase in homosexuality. Most of the rapid growth was in the first 315 days, but between 315 and 600 days, population growth slowed and violence became more prevalent. His most well known experiment was in 1968 on mice, which was designed to hold nearly 4,000 mice but the population maxed out at 2,200. This phrase, "behavioral sink" is commonly associated with Calhoun's experiments.
#RAT UTOPIA EXPERIMENT SERIES#
Even in the absence of the behavioral sink, in the second series of three experiments, infant mortality reached 80 percent among the corresponding members of the experimental populations." In the experiments in which the behavioral sink developed, infant mortality ran as high as 96 percent among the most disoriented groups in the population. "But the same pathological "togetherness" tended to disrupt the ordered sequences of activity involved in other vital modes of behavior such as the courting of sex partners, the building of nests and the nursing and care of the young. As a result extreme population densities developed in the pen adopted for eating, leaving the others with sparse populations." Individual rats would rarely eat except in the company of other rats. As many as 60 of the 80 rats in each experimental population would assemble in one pen during periods of feeding. The animals would crowd together in greatest number in one of the four interconnecting pens in which the colony was maintained. "The common source of these disturbances became most dramatically apparent in the populations of our first series of three experiments, in which we observed the development of what we called a behavioral sink. The social organization of the animals showed equal disruption." Among the males the behavior disturbances ranged from sexual deviation to cannibalism and from frenetic overactivity to a pathological withdrawal from which individuals would emerge to eat, drink and move about only when other members of the community were asleep.
/https://tf-cmsv2-smithsonianmag-media.s3.amazonaws.com/filer/7c/36/7c36a5fc-01a8-4877-aeb4-ad87704efcf2/calhounj.jpg "rat utopia experiment")
An even greater number, after successfully giving birth, fell short in their maternal functions.
#RAT UTOPIA EXPERIMENT FULL#
Many were unable to carry pregnancy to full term or to survive delivery of their litters if they did. "The consequences of the behavioral pathology we observed were most apparent among the females. 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. Of these initial rat experiments Calhoun wrote: Calhoun began performing experiments on populations of rats to see what would happen if all of their resources were unlimited and they were kept safe from predators, diseases, weather, etc. Many of you have probably heard of this experiment, but the short introduction is that starting in 1958, a researcher named John B.
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