For the population of mice, as part of a social experiment, paradise conditions were created: unlimited supplies of food and drink, the absence of predators and diseases, and sufficient space for reproduction. However, as a result, the entire colony of mice died out. Why did this happen? And what lessons should humanity learn from this?
American ethologist John Calhoun conducted a series of amazing experiments in the 60s and 70s of the twentieth century. D. Calhoun invariably chose rodents as experimental subjects, although the ultimate goal of research has always been to predict the future for human society. As a result of numerous experiments on rodent colonies, Calhoun formulated a new term, «behavioral sink» (behavioral sink), denoting the transition to destructive and deviant behavior in conditions of overpopulation and crowding. John Calhoun gained some notoriety for his research in the 60s, as many people in post-war baby boom Western countries began to think about how overpopulation would affect institutions and individuals in particular.
He conducted his most famous experiment, which made an entire generation think about the future, in 1972 with the National Institute of Mental Health (NIMH). The purpose of the experiment «Universe-25» was to analyze the effect of population density on the behavioral patterns of rodents. Calhoun built a veritable paradise for mice in a lab setting. A tank was created with dimensions of two by two meters and a height of one and a half meters, from which the test subjects could not get out. Inside the tank, a constant temperature comfortable for mice (+20 °C) was maintained, food and water were abundant, and numerous nests for females were created.
Every week the tank was cleaned and maintained in constant cleanliness, all the necessary security measures were taken: the appearance of predators in the tank or the occurrence of mass infections were excluded. The experimental mice were under the constant supervision of veterinarians, their health status was constantly monitored. The food and water system was so thought out that 9500 mice could feed at the same time without experiencing any discomfort, and 6144 mice could drink water without experiencing any problems. There was more than enough space for mice, the first problems of lack of shelter could only arise when the population reached over 3840 individuals. However, there have never been such a number of mice in the tank; the maximum population size was noted at the level of 2200 mice.
The experiment started from the moment four pairs of healthy mice were placed inside the tank, which took quite a bit of time to get used to, realize what mouse fairy tale they were in, and begin to multiply rapidly. Calhoun called the period of development phase A, but from the moment the first cubs were born, the second stage B began. This is the stage of exponential population growth in the tank under ideal conditions, the number of mice doubling every 55 days. Starting from the 315th day of the experiment, the population growth rate slowed down significantly, now the number doubled every 145 days, which marked the entry into the third phase C. At this moment, about 600 mice lived in the tank, a certain hierarchy and a certain social life were formed. There is physically less space than there was before.
There was a category of «outcast», who were driven to the center of the tank, they often became victims of aggression. It was possible to distinguish a group of «outcasts» by bitten tails, torn hair and traces of blood on the body. The outcasts consisted primarily of young individuals who had not found a social role for themselves in the mouse hierarchy. The problem of the lack of suitable social roles was caused by the fact that under ideal tank conditions, mice lived for a long time, aging mice did not make room for young rodents. Therefore, aggression was often directed at new generations of individuals born in the tank. After the expulsion, the males broke down psychologically, showed less aggression, did not want to protect their pregnant females and perform any social roles. Although from time to time they attacked either other individuals from the “outcast” society, or any other mice.
Females preparing for birth became increasingly nervous, since as a result of the increase in passivity among males, they became less protected from random attacks. As a result, females began to show aggression, often fight, protecting offspring. However, paradoxically, aggression was not directed only at others, no less aggressiveness was manifested in relation to their children. Often the females killed their young and moved to the upper nests, became aggressive hermits and refused to breed. As a result, the birth rate has fallen significantly, and the mortality of young animals has reached significant levels.
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Soon the last stage of the existence of the mouse paradise began — phase D or the phase of death, as John Calhoun called it. The symbol of this stage was the emergence of a new category of mice, called «beautiful». These included males demonstrating behavior uncharacteristic for the species, refusing to fight and fight for females and territory, showing no desire to mate, prone to a passive lifestyle. The «beautiful» only ate, drank, slept and cleaned their skin, avoiding conflicts and performing any social functions. They got this name because, unlike most other inhabitants of the tank, their body did not have traces of fierce battles, scars and torn hair, their narcissism and narcissism became legendary. The researcher was also struck by the lack of desire among the “beautiful” to mate and breed, among the last wave of births in the tank, “beautiful” and single females refusing to breed and fleeing to the upper nests of the tank became the majority.
The average age of a mouse in the last stage of the existence of mouse paradise was 776 days, which is 200 days more than the upper limit of reproductive age. The mortality of young animals was 100%, the number of pregnancies was insignificant, and soon amounted to 0. Endangered mice practiced homosexuality, deviant and inexplicably aggressive behavior in an abundance of vital resources. Cannibalism flourished with a simultaneous abundance of food, females refused to raise cubs and killed them. Mice are rapidly dying out on the 1780th day after the start of the experiment, the last inhabitant of the «mouse paradise» died.
Anticipating such a catastrophe, D. Calhoun, with the help of a colleague, Dr. H. Marden, conducted a series of experiments in the third stage of the death phase. Several small groups of mice were removed from the tank and relocated to equally ideal conditions, but also in conditions of minimal population and unlimited free space. No crowding and intraspecific aggression. In fact, the “beautiful” and single females were recreated the conditions under which the first 4 pairs of mice in the tank exponentially reproduced and created a social structure. But to the surprise of scientists, the “beautiful” and single females did not change their behavior, refused to mate, breed and perform social functions associated with reproduction. As a result, there were no new pregnancies and the mice died of old age. Similar similar results were observed in all resettled groups. As a result, all experimental mice died under ideal conditions.
John Calhoun created the theory of two deaths based on the results of the experiment. The «first death» is the death of the spirit. When newborn individuals no longer had a place in the social hierarchy of the «mouse paradise», there was a lack of social roles in ideal conditions with unlimited resources, an open confrontation between adults and young rodents arose, and the level of unmotivated aggression increased. Growing populations, increased crowding, increased levels of physical contact, all this, according to Calhoun, led to the emergence of individuals capable of only the simplest behavior. In an ideal world, in safety, with an abundance of food and water, the absence of predators, most individuals only ate, drank, slept, looked after themselves. A mouse is a simple animal, for it the most complex behavioral models are the process of caring for a female, reproduction and care for offspring, protection of territory and cubs, participation in hierarchical social groups. Psychologically broken mice refused all of the above. Calhoun calls this abandonment of complex behavioral patterns «the first death» or «the death of the spirit.» After the onset of the first death, physical death (the «second death» in Calhoun’s terminology) is inevitable and is a matter of a short time. As a result of the «first death» of a significant part of the population, the entire colony is doomed to extinction even in the conditions of «paradise».
Calhoun was once asked about the reasons for the appearance of a group of rodents «beautiful». Calhoun drew a direct analogy with a person, explaining that the key feature of a person, his natural destiny is to live in conditions of pressure, tension and stress. Mice that refused to fight, choosing the unbearable lightness of being, turned into autistic «beauties», capable of only the most primitive functions, eating and sleeping. The «beauties» refused everything complex and demanding tension and, in principle, became incapable of such a strong and complex behavior. Calhoun draws parallels with many modern men, capable of only the most routine, everyday activities to maintain physiological life, but with an already dead spirit. What is expressed in the loss of creativity, the ability to overcome and, most importantly, to be under pressure. Refusal to accept numerous challenges, escape from tension, from a life of struggle and overcoming — this is the «first death» in John Calhoun’s terminology or the death of the spirit, followed by the inevitable second death, this time of the body.
Perhaps you still have a question why D. Calhoun’s experiment was called «Universe-25»? This was the twenty-fifth attempt by the scientist to create a paradise for mice, and all previous ones ended in the death of all experimental rodents …