Calhoun's work became used as an animal model of societal collapse, and his study has become a touchstone of urban sociology and psychology in general.
In the 1962 study, Calhoun described the behavior as follows:
Many [female rats] were unable to carry pregnancy to full term or to survive delivery of their litters if they did. An even greater number, after successfully giving birth, fell short in their maternal functions. 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. The social organization of the animals showed equal disruption.
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 animals would crowd together in greatest number in one of the four interconnecting pens in which the colony was maintained. As many as 60 of the 80 rats in each experimental population would assemble in one pen during periods of feeding. Individual rats would rarely eat except in the company of other rats. As a result extreme population densities developed in the pen adopted for eating, leaving the others with sparse 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.
So what exactly happened in Universe 25?
After day 315, population growth slowed. More than six hundred mice now lived in Universe 25, constantly stroking their shoulders as they walked up and down the stairs to eat, drink, and sleep. The mice were found born into a world that was fuller every day, and there were far more mice than there were significant social roles. With more and more peers to defend against, the men found it difficult and stressful to defend their territory, so they abandoned the activity. Normal social discourse within the mouse community was broken, and with it the ability of mice to form social bonds. Failures and dropouts congregated in large groups in the middle of the compound, their listless retreat punctuated occasionally by spasms and waves of senseless violence. The victims of these random attacks became attackers. Left alone in nests subject to invasion, the lactating females attacked their own young. Procreation plummeted, infant neglect and mortality skyrocketed. The solitary females retreated to isolated nests on the attic levels. Other men, a group Calhoun called "the beautiful ones," never sought sex and never fought, they simply ate, slept, and groomed, wrapped in narcissistic introspection. Elsewhere, cannibalism, pansexualism, and violence have become endemic. The mouse society had collapsed.
