For many years, mice have been used as a replacement for humans to perform various physical and psychological experiments. This was done to determine the possible reaction of people to certain changes in their society or environment. From trying to graft ears onto their heads to being used in mental experiments to satiate the curiosity of scientists regarding certain questions about the human condition, mice have been subjected to all sorts of experiments. 

There are several reasons people have, for the last few centuries at least, been using mice for their experiments. One of those facts is that their genetic makeup, biology, and social behaviors mimic those of humans. They are mammals just like us. Their endocrine systems are similar to those of humans and the way they show symptoms of diseases is also pretty comparable to humans. Plus their small sizes and short lifespan, coupled with their aging process, make them an ideal candidate for experimentation. Mouse experiments have actually led to a lot of breakthroughs and advancements in medicine and cancer research.

So it goes without saying that they would be used in an experiment on the effects of population density. The experiment in question was conducted in the fifties by a scientist named Dr.John Calhoun. He first created a space called the ‘Mouse Utopia’, but it soon became apparent that this so-called utopia had ended in disaster. Thus the name of the experiment became known as the ‘Behavioral Sink’. It was called so because over time, the behavioral patterns of the mice sunk more and more towards violence in this overpopulated place where they essentially had no escape from each other. 

The experiment was basically a means of testing how mice reacted to having unlimited resources with the single limiting factor being the space they had. How would their society react to the high population density? And based on those reactions, what might be said for human beings and our societies, if we were to experience similar conditions of high population limited to a small space? These experiments shed light on some very disturbing revelations which became a means of justification when it came to birth control as well as giving urban planners insight by the  scientists and politicians of the time.

The experiment, begun in the fifties by Dr. John Calhoun of the National Institute of Health in Washington D.C and then his colleagues, was performed on white mice. It was completed over a span of several years in order to study the effects of overpopulation and high population density on the individual social behaviors of the mice.

Their findings were these:  

in an environment with unlimited resources but limited space, the population of mice would first explode, then it would slow down and peak out, then eventually their society would collapse to the point of extinction.

The Experiment 

The initial population of mice was introduced to an environment of 16 cells that would be considered a mouse utopia: conditions of comfort, nutrition, and housing were well provided for a population of over three thousand mice. The individual mice were kept track of by using color markings on their fur. The natural factors that usually help control the populations such as disease and predators like owls or cats were completely eliminated.  So this mouse universe in a way was designed to simulate the then present situations of the continuously increasing human population (which to this day, continues to increase daily).

The results were disastrous.

Strive Period 

The doctor gave different names to different phases of the experiment based on the mices’ behavior. The first period is called strive, as the mice started to adjust to their new surroundings and strove to establish social order, their nests, and territories. The strive period lasted for the first hundred days of the experiment. 

Exploit Period 

The second period of this experiment, dubbed as the exploit period, lasted around two hundred and fifty days. During this time the mouse population exploded, doubling almost every sixty days. This was the time period in which their use of resources became unequal. Each mouse was equal in terms of their physical structure as a living unit, however, in some areas of the little utopia more food and water were consumed as compared to others. As more mice were added into the fray because of their ever-increasing population, most of them began to link eating and drinking with the presence of others. This ultimately led to the issue of crowding in some areas. 

Equilibrium Period

The next period was called the equilibrium period as this was the time when the population increase slowed down and thus the population leveled off. Since by this time most of the space had already been divided amongst the previous generations, these newer baby mice were more inhibited. By now some mice began to exhibit behavior that differed from the norm. There were excess males, who tried to strive for acceptance but they got rejected and thus withdrew. Added to that, the mice were starting to get more violent. The effects became more and more visible. Certain mice were repeated targets of these bouts of violence. They would have badly chewed and scarred tails.

 On the other hand, there were certain mice whose behavior was completely different from the rest. These ones have been dubbed by Dr. Calhoun as ’the beautiful ones’. The only thing these mice did was groom themselves, sleep, and eat. While the rest of the population was out in the main squares and social areas, annoyed by constant exposure to each other and social interactions, these mice were safe in their little spaces. What happened essentially was that a group of very aggressive male mice had sequestered off the little ‘condos’ or rooms where they kept these ‘beautiful ones’.

Their main feature was essentially, their laziness. They never involved themselves with the other mice. They did not interact, mate, or fight with the other mice. So as the conditions of the larger populations began to worsen, these ones stayed safe in their isolation. They looked beautiful, perhaps, but they were not keen or sharp, as they would have no idea how to react to any external stimuli that might ever endanger them. 

The Die Period

The final part of the experiment was called the die period. It is pretty self-explanatory: this is the point where the populations started to die and eventually went extinct, despite their plethora of resources. The population’s decline began just after about twenty-two hundred mice. Despite the fact that they were pushed closer to each other than ever before, during the shifting from the equilibrium period to the die period, each mouse became less aware of its associates. One might say they began to learn, or at least they tried to, ignore each other. According to Calhoun’s conclusions, the mice were unable to have this constant exposure and forced social interaction with each other. They could not deal with it. There was more violence now than ever before, with a large percentage of the population showing fighting scars on their bodies and marks on their tails. Eventually, all of them died. Their social order completely collapsed and they turned on each other, sick and exhausted, unable to cope with the constant interaction. 

The Mouse Utopia experiment is a classic example of how a typical population and its unchecked, unmonitored growth might affect people. After the first experiment, research in this area continued under Dr. Calhoun’s supervision. Dr. James Bill took the basics of this experiment and then tried to use them to study the intricacies of social behavior in greater depth. These studies used animals, yes, but he argued that the findings on the way that unchecked population growth and its high-density affect society were things that might be applied to human societies as well. 

Many researchers believe that the human race has reached a point in our population growth that is crucial and that might affect our very future as a species on this planet. This is not unlike the other populations of species that have lived on this planet. This is a point, according to these researchers, where important decisions must be made. They believe that we must make sure to plan the population growth carefully if we want the human population to be able to strive. Studying other creatures, plants and animals alike, helps us to be able to use the findings as a guide to making our future decisions for the population in order to be able to maintain our balance with nature. 

A lot of people believe that the Behavioral Sink of the Mouse Utopia experiment is a grim prediction of how the human population will eventually turn out due to overcrowding and overpopulation.  We are social animals, but we need our own space, otherwise, we become anti-social. That being said, the Mouse Utopia experiment is not an accurate portrayal of how our society might end up, as it lacks the outside factors and errors that occur in daily human life. The experiment was performed in very tight, controlled conditions, but human populations don’t exist in such exact conditions. However, the overall effects, or at least a part of them, might be predicted by this experiment. 

Something important to take into consideration is the limiting factor in this experiment: space. All the other resources were provided for, but the mice became irritable and violent because of the lack of space they had away from each other. This shows the importance of space as being one of the most important, decisive factors in the development of animals’ social behaviors, including that of Man. As more time went by without having any space, the negative behaviors of the previous generation of mice began to be passed onto the next generation. Thus a cycle began. This shows the adverse consequences of a high-density population. 

A similar condition to the Mouse Utopia experiment that human beings were subjected to was explained by Quintus Curtius in an article titled ‘The Power of Choice’. This was done on the people of Easter Island.  When they first arrived there in 900 A.D, the island was full of trees, capable of sustaining a high population. No external factors like predators or disease plagued the humans, and the resources were seemingly endless. They basically had their own little utopia. However, similar to the Behavioral Sink, as the island’s population grew to a larger amount and covered only half of the island, the humans began to become more and more savage, until finally, their society too, collapsed. 

The article explains that as more and more people began to live there, the competition for resources became much more severe and ferocious. People would fight each other far more. There were more inter-tribal hostilities and wars, and the overall feeling on the island began to be one that lacked safety. Eventually, there were so many trees cut down that the islanders became trapped on the island, unable to escape this place that had become a living hell for them. Eventually, it got to the point where the islanders turned on each other completely as their need for survival trumped everything else, including their humanity. They began to turn towards cannibalism to survive instead of letting themselves die of starvation. A quote from the article says “Perhaps the islanders compensated for their misery by focusing more and more on the empty ritual of building and raising statues, as their means of sustenance melted away.”

A morbid, depressing thought indeed.

One might argue against such consequences ever becoming a reality because human beings come wired with brains for rationality and the power of choice. There are still so many areas of land where a soul has not yet stepped foot, and thus they remain uninhabited. One can argue that to avoid such violence, humans can just expand their territories and move to these unexplored areas. However the chilling thing about the situation on the island is that half of the island was still uninhabited by human beings, yet they persisted in their violence and competition. So all of this just goes to show that human beings as well as other animals- have a limited capacity for social interaction. All individuals need to have their own space and alone time for the sake of their sanity and rationality. 

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Dusty Showers has been in the urban nuisance wildlife and pest control field since 1993. Taught by Garon Fyffe, a pioneer in humane nuisance wildlife management, Dusty has a passion for finding humane solutions to human & wildlife conflicts. Dusty was the only individual invited by the Florida Fish & Wildlife Commission in the lat 1990's to help write legislation for legal protection of Florida bats. With an instinct for solving wildlife, Dusty found pest control to be an easy "add-on interest". Dusty started his first business "Animal Instincts Wildlife & Pest Management" in the Tampa Bay, Florida area in 1995. Eventually selling Animal Instincts in 2002, Dusty went on to start Creepy Creatures Termite and Pest Control in 2009, which he still owns and operates today in Palm Harbor, Florida.

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