Experiment Calhoun: the problem of overpopulation for example, the «mouse Paradise»

© Fotolia / JacobSTЛабораторная mouse. Archival photoExperiment Calhoun: the problem of overpopulation for example, the «mouse Paradise»© Fotolia / JacobST

In most cases, the fate of mice is unenviable, but John Calhoun in 1968 tried to create for them a truly paradisiacal conditions in the experiment, the «universe 25». The result of this venture was very unexpected, and, possibly, the people have nothing to worry about in this regard.

For the experiment were taken, four females and four males mice. Especially for them was equipped with a special «closed universe» — tank-a box with sides 2,5×2,5×1,5 meters. Mice were provided with regular food and drink. Each of them had their own «living space» — a small capsule, where mouse could be free from feeding time. The purpose of the experiment, which was conducted at the National Institute of mental health, was the analysis of population development in such favorable conditions.

© Fotolia / lculigМыши. Archival photoExperiment Calhoun: the problem of overpopulation for example, the «mouse Paradise»© Fotolia / lculigМыши. Archive photo

Limit for the population, according to scientists, was the number at nine and a half thousand individuals, if we take into account how fed animals. Water enough every day to drink a little more than six thousand mice. However, at the peak of the experiment, the population was 2,200 animals.

All Calhoun have identified four stages of development of mouse heaven. The period from the beginning to the emergence of the first young scientist called stage A. After that, B-stage, the number of mice doubled every 55 days. On stage, when the tank lived 620 mice, the rate of growth of population slowed down. Now she has doubled every 145 days, and the mice began to form a social hierarchy. Some young males of their race were cast out to the perimeter of the tank.

«Les Miserables» mouse, canine companions wounded, «psychologically break». Some of them became passive, others – on the contrary, overly aggressive, they often attack other mice. Because of this increased risk to pregnant females. In the end, they (not the males) themselves began to behave aggressively and defend their territory. Sometimes they attacked their own children. Because of this, in the population the birth rate has fallen, and the mortality rate of the young increased significantly.

© Fotolia / Vadim FogelКрысаExperiment Calhoun: the problem of overpopulation for example, the «mouse Paradise»© Fotolia / Vadim FogelКрыса

Phase D was the final stage of the existence of the mouse Paradise. By the time of its inception, the number of mice began to decline. Females almost ceased to give birth, and the males formed a group, which the author of the experiment called «beautiful». Unlike the rogue, they didn’t have scars, but they didn’t even try to leave behind offspring. All the time they spent eating, sleeping and preening fur.

In 1972, Calhoun made the decision to end the experiment. The tank was only 22 males and 100 females. By this time individuals were not able to produce offspring that would be able to revive the population.

The scientist foresaw such an outcome and during the third phase tried with a small group of mice re-start the process of creating population. However, the animals remained loyal to the patterns of behavior he learned in the tank.

The results of these experiments Calhoun came to the conclusion that achieving a certain density of population and the filling of social roles in the population leads to the disintegration of society due to the emergence of a layer of «rogue». They are forced to compete with older males, society is experiencing a «death of spirit».

© Photo : Alexxai Kravitz Thin and thick mouseExperiment Calhoun: the problem of overpopulation for example, the «mouse Paradise»© Photo : Alexxai Kravitz Lean and fat mouse

Today, some scientists, taking into account statements about the overpopulation of the Earth, talking about the possibility of repeating that scenario for people. The scientist himself said that by 1984 humanity may pass the point of no return. However, it should also be noted that Calhoun’s experiment was criticized for some points.

Cleaning the tank was carried out approximately every six to eight weeks. During this time it accumulated a large amount of waste mice that could contribute to the spread of infections. Some scientists have noticed that the conditions of detention of mice could result in the spread of disease – as noted by Calhoun himself, in summer, the temperature in the tank could rise to 32 degrees Celsius, which is not conducive to the breeding of mice.

Many also criticize the experiment because the founders of the population was akin to the mouse, and that is why their offspring may not be able to create a stable population.

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