![]() 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. An even greater number, after successfully giving birth, fell short in their maternal functions. Many were unable to carry pregnancy to full term or to survive delivery of their litters if they did. In the 1962 study, Calhoun described the behavior as follows: ![]() He would later perform similar experiments on mice, from 1968 to 1972.Ĭalhoun'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. Calhoun coined the term "behavioral sink" in his Februreport in an article titled "Population Density and Social Pathology" in Scientific American on the rat experiment. In the experiments, Calhoun and his researchers created a series of "rat utopias" – enclosed spaces in which rats were given unlimited access to food and water, enabling unfettered population growth. The term and concept derive from a series of over-population experiments Calhoun conducted on Norway rats between 19. Calhoun to describe a collapse in behavior which can result from overcrowding. " Behavioral sink" is a term invented by ethologist John B. (2013).Conceptual collapse in behavior which can result from overcrowding 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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