Calhoun, John (ethologist)

In the years 1947-1949, Calhoun, as part of a project on the study of rodent ecology conducted by Johns Hopkins University , observed gray rats in their natural environment - in a fenced open-air enclosure of 10 thousand square feet (930 m ² ). Although the number of rats in a pen of such sizes with uncontrolled breeding could theoretically reach 5 thousand, Calhoun noted that the population size for the entire experiment did not exceed 200 individuals and stabilized at a value of 150 individuals. Moreover, the rats did not randomly disperse along the corral, but formed 12-13 organized colonies, each of which had 12 rats. Calhoun suggested that this is precisely the size of the group that is the best for gray rats — if this amount is exceeded, stress leads to the breakup of the group.

From 1958 to 1962, Calhoun conducted a series of experiments with gray rats already in an artificial environment - a laboratory built in a laboratory of 12 m ^{2 in area} , up to 1.5 meters high, divided into 4 compartments communicating with each other, with two end compartments - the first and fourth - had no communication with each other. The landfill was isolated from the outside world, supplied with food and water in unlimited quantities. Populating this “rat paradise”, Calhoun investigated the changes in the behavior of rats depending on the natural changes in their population. A group of 12 rats, a total of 48 individuals, was placed in each of the four compartments. To prevent excessive overpopulation, upon reaching the number of 80 individuals, the researchers removed from the landfill extra young rats that survived their infancy. It turned out that the final compartments were captured by strong male leaders, each of whom lived in a harem of 8-12 females, and expelled other males to the central compartments. About 60 rats that were crowded in the central compartments showed various forms of deviant behavior: increased aggression and causeless attacks on each other, loss of interest in mating, attempts to mate with all females or even with all rats in a row, regardless of gender. Cannibalism was observed (in particular, eating rat pups) even in conditions of abundance of food ^[2] .

Calhoun's most famous series of experiments, in which population growth was not limited in any way, was put on mice. The conditional name of the experiment is “ Universe 25 ” ( Eng. Universe 25 ), and the number “25” is the number of times the experiment was repeated. In July 1968, 4 pairs of mice were placed in a wire enclosure in a laboratory at the National Institute of Mental Health . The paddock with 256 nest boxes, each of which was designed for 15 mice, was equipped with water and feed dispensers and enough material to build nests. Calhoun described the corral as a “ utopia ” for mice: according to researchers, the place for nests in the corral would be enough for 3840 mice, and constantly served food - for 9500. In practice, the population stopped at a maximum value of 2200 individuals and only decreased after it. By June 1972 , when Calhoun completed the experiment, only 122 mice that were of reproductive age remained in the pen. Therefore, the outcome of the experiment was already clear.

Calhoun called stage A the first four pairs of mice. Stage B began from the moment the first cubs were born. This is the stage of the exponential growth of the population in the tank under ideal conditions - the number of mice doubled every 55 days. Starting from the 315th day of the experiment, the population growth rate slowed down significantly, and the number of mice doubled every 145 days. The third stage (C) of the experiment began. At that moment, 620 mice lived in the tank, and a certain social hierarchy was formed. A category of young males appeared who did not find a social role for themselves in the mouse hierarchy in the colonies around the perimeter of the corral and expelled to the center of the tank. One could distinguish the group of “outcasts” by their bitten tails, torn hair and traces of blood on the body. The problem of the lack of suitable social roles was caused by the fact that in ideal conditions the tank of the mouse lived for a long time, aging mice did not make room for young rodents. After the exile, the males broke psychologically, characterized by passivity or excessive aggressiveness with an attack on any other mice. Pregnant females became less protected from accidental attacks. As a result, they themselves began to show aggression, it was they - not the males - who began to actively defend their territory, while aggression manifested itself in relation to their children. As a result, the birth rate has fallen significantly, and the mortality rate of young animals has reached significant levels.

Soon the last stage of the existence of a mouse paradise began - phase D or the phase of death, as John Calhoun called it. At this stage, Calhoun observed an increase in the number of another group of males, whom he called " beautiful " ( English beautiful ones ), due to the absence of wounds and scars. These mice did not enter the struggle for females and territory, did not show activity for reproduction, and only ate, slept, and cleaned the fur. Females also stopped mating with males. Calhoun’s colleague, Dr. Halsey Marsden, in 1972 transferred several females and “handsome” males to separate pens, finding that the mice did not try to mate there either.

According to the results of the study, Calhoun concluded that when a certain population density is exceeded and all social roles in the population are filled in, a growing layer of young “outcasts” appears. Intense competition between them and older individuals leads to the breakdown of social ties and the collapse of society as a whole, and a transition to a state where, with low mortality, the norm becomes primitive " autistic " behavior, leading to the extinction of the population. Using a reference to the Revelation of John the Theologian , Calhoun described the collapse of society as “death squared” ( English death squared ), while the “first death”, the death of the spirit, the mice experienced during their lifetime ^[1] .

The famous experiment was later used as the basis for the development of the concept of proxemics by Edward Hall . The concept of behavioral cesspool also influenced the development of the sociology of the city ^[4] and psychology.

Calhoun's developments have influenced research on aggression .

Criticism of the Universe 25 experiment

1. There is no information about the origin of the first 8 mice that gave rise to the entire population. In particular, it was not checked whether they are twin brothers and sisters from the same litter. Closely related could have the most negative impact on all subsequent generations of mice.
2. The temperature in the paddock could reach +32 degrees, which is unfavorable for mice.
3. The pen was cleaned once every 1-2 months, that is, the mice spent most of the time in a room contaminated with feces, urine, corpses, and food debris ^[1] .
4. There is no exact description of the methods for counting mice. Estimates are given approximately.
5. At the last stage, Calhoun describes the appearance of a group of “handsome mice” (mice did not fight for females and territory, did not show activity for reproduction and only ate, slept and cleaned their fur ...), noting such behavior as abnormal, but the age of these mice. However, it was indicated that the average age of the mice in the last stage was 770 days. By this time, the reproductive period in males has long been completed, and the described behavior is normal for them.
6. The causes of death and infertility of females have not been sufficiently investigated. The corral was not protected from any infections that could affect mortality and reproductive function.

Misconceptions about experiments

• The conclusion is incorrect that the larger the population, the stronger the tendency to its degradation. Calhoun set the main task to study the behavior of mice in crowded conditions: the mice had unlimited access to food and water, but the territory, which is an equally important factor for normal existence, was reduced to a minimum. When the territory is not limited, population growth under ideal conditions can continue almost indefinitely without social and genetic consequences (a demographic explosion of a rabbit population in Australia can be an example of this).

Based on Calhoun’s work, the book “ Mrs. Frisby and the Rats of NIMH "And filmed the cartoon" The Secret of Rats . "

• Proxemics

Books

• Calhoun, John. Crowding and social behavior in animals. - Anchor Books, 1947-1948.
• Calhoun, John. Environment and Population: Problems and Adaptation: An Experimental Book Integrating Statements by 162 Contributors. - Praeger, 1983. - P. 486. - ISBN 0-275-90955-7 .

Articles

• Calhoun, John. The Study of Wild Animals under Controlled Conditions // Annals of the New York Academy of Sciences. - 1950. - Vol. 51. - P. 113–22.
• Calhoun, John. The Social Aspects of Population Dynamics / American Society of Mammalogists // Journal of Mammalogy. - 1952. - Vol. 33, no. 2. - P. 139–159. - DOI : 10.2307 / 1375923 . - .
• Calhoun, John. A Behavioral Sink // Roots of Behavior / ed. by Eugene L. Bliss. - New York: Harper & Brothers, 1962. - Ch. 22.
• Calhoun, John. Population density and social pathology // Scientific American . - 1962. - Vol. 206, no. 2. - P. 139–148. - PMID 13875732 .
• Calhoun, John. Plight of the Ik and Kaiadilt is seen as a chilling possible end for Man // Smithsonian Magazine. - 1972. - Vol. 3. - P. 27–32.