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© Robert Sommers 2018

Monday, April 23, 2018

Behavioral Sink

There was an interesting letter to the editor in the Los Angeles Times the other day from a man named Buz Wolf in Studio City.
To the editor: John B. Calhoun, an ethologist, conducted research on the effects of population density in his 1968 experiment, the "mouse universe." He created a habitat for mice where the only restriction was space.
He began by introducing four pairs of mice. The population reached 620 by day 315, after which the population growth dropped markedly. Between then and day 600, the mice's social structures and behaviors broke down. Breeding never resumed and behavior patterns changed.
The conclusion? When all the space is taken and all the social roles are filled, competition and stress will be such that society will break down and the population will collapse.
The Times Editorial Board, the state and city planners keep emphasizing the housing shortage and the need to build more capacity. Unlike the "mouse universe," this increased capacity will create additional, perhaps unattainable, demands on infrastructure, on water and food delivery, on sewage treatment and on transportation.
When will Los Angeles reach its day 600?
Buz Wolf, Studio City
This letter got me to thinking a little bit. First off I had never heard of ethology. And I live in a county where housing is expensive and social engineers tend to want to build more and more without considering what happens to the native eco system and the scarcity of water. Is there a tipping point where life becomes unlivable and there is a collapse like what happens to the mice colony?

Calhoun - Yoichi Okamoto 

I decided to do a little research on John B. Calhoun this morning. He was an early birder from Tennessee who moved to Maryland and started studying rodents at John Hopkins in 1946. I didn't find any specific info on his 1968 experiment but now know that the study the letter writer cites started on Norway Rats from 1958 to 1962 and that he started working on lab mice from 1968 to 1972 while at the National Institute for Mental Health.

Calhoun coined the term Behavioral Sink to describe a behavioral collapse that was a result of overcrowding. The term was first used in February 1, 1962 report in an article titled Population Density and Social Pathology in Scientific American.
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.
Calhoun's experiments with the rodents started out with them living in spacious, utopian quarters and he watched the dire consequences as the space was reduced and things got more and more compressed.
Initially, the population grew rapidly, doubling every 55 days. The population reached 620 by day 315, after which the population growth dropped markedly, doubling only every 145 days. The last surviving birth was on day 600, bringing the total population to a mere 2200 mice, even though the experiment setup allowed for as many as 3840 mice in terms of nesting space. This period between day 315 and day 600 saw a breakdown in social structure and in normal social behavior. Among the aberrations in behavior were the following: expulsion of young before weaning was complete, wounding of young, inability of dominant males to maintain the defense of their territory and females, aggressive behavior of females, passivity of non-dominant males with increased attacks on each other which were not defended against.[2]
After day 600, the social breakdown continued and the population declined toward extinction. During this period females ceased to reproduce. Their male counterparts withdrew completely, never engaging in courtship or fighting. They ate, drank, slept, and groomed themselves – all solitary pursuits. Sleek, healthy coats and an absence of scars characterized these males. They were dubbed "the beautiful ones." Breeding never resumed and behavior patterns were permanently changed.
The conclusions drawn from this experiment were that when all available space is taken and all social roles filled, competition and the stresses experienced by the individuals will result in a total breakdown in complex social behaviors, ultimately resulting in the demise of the population.
Calhoun saw the fate of the population of mice as a metaphor for the potential fate of man. He characterized the social breakdown as a "second death," with reference to the "second death" mentioned in the Biblical book of Revelation 2:11.[1] His study has been cited by writers such as Bill Perkins as a warning of the dangers of the living in an "increasingly crowded and impersonal world."[3]
We forget about Calhoun's work at our peril.

1 comment:

Jon Harwood said...

"That which cannot go on forever will stop". Herbert Stein