What Is Behavioral Sink?

As much as the idea of living in a utopia sounds like a dream, something to strive for as a planet, a world of complete happiness and tranquility: the reality is that we would probably struggle just as much as we are now to survive. Despite how perfect external circumstances and factors could present themselves, an individual’s reaction to being around others plays a significant role in their perception of their surroundings. It is in the nature of all things living to gravitate towards chaos when massed together. 

This phenomenon is something recorded by ethologist (someone that studies animal behavior) John Calhoun, who spent the majority of his career researching what he referred to as a “behavioral sink.” The term behavioral sink can be used to describe the correlation between collapse in behavior and overpopulation. This implies that population density can lead to the breakdown of instincts and basic functioning within a society, regardless of external conditions. 

Throughout his career, Calhoun performed intense research on population control and density, conducting a plethora of population experiments on various rodents such as mice and rats to gather data for his theories on behavioral sink and the possible implications it could have on mankind. 

Mouse Utopia
Screen Shot 2020-08-06 at 2.46.16 PM

Understanding Population Density and Overcrowding 

Although overcrowding and population density sound like two terms to convey the same meaning, it is important to understand the clear distinction between the two. For example, if 10 people step into an elevator, the space would be considered densely populated. There are clearly too many people taking occupancy in such a small space. Therefore, as a result of this density, crowding begins. Crowding refers to how the humans cram together due to the population density, invading each other’s personal space. It can be said that population density is what leads to overcrowding. 

Now that you understand the difference between population density and crowding, let’s look at another example on a larger scale. Elevators only serve as a liminal space to quickly transport someone from one destination to the next over a duration of minutes or less, so let’s imagine something bigger and lengthier in time such as a college frat party. 

As individuals, everyone has their own reaction to being in a crowded space. At a frat party, there are going to be multiple social bonds to consider: people who know each other briefly in passing, people who came with their close friends, and people who are complete strangers. People who are barely acquainted may have introductions and get to know everyone better, interacting with the masses and making their way around the space forming new social bonds. People who arrived in groups may stick to their pack, crowding into the main areas of the house but being reclusive of others joining their tight group. People who are complete strangers may choose to stick to the corners of the room, isolating themselves outside of the crowd and coexisting with others without interacting. 

There would be crowds of people (both strangers and friends alike) who would dance in the easiest accessible areas, people having food and drinks in the kitchen together, pairs sneaking upstairs to bedrooms, and even people who argue and break out into physical fights for seemingly no reason. The hosts of the party might even try to remain the center of attention, reinforcing the social hierarchy that this is their party and they’re running the show. 

As it’s clearly seen in this example of just one night at a party, heavily populated social surroundings greatly influence the way various individuals react in their shared space. Being crowded together heavily impacts each person’s social habits and behaviours, dictating how they spend their time amongst others and the level at which they interact socially. 

This natural mental reaction to being overcrowded is exactly what Calhoun was so interested in learning more about throughout the course of his research. Essentially, all of Calhoun’s experiments involved putting rodents together in a fixed environment, letting things play out without outside interference, and observing how the steady rise in population started to affect behaviour when exposed to that environment over a lifetime. 

Behavioral Sink In Calhoun’s Experiments

Although Calhoun ran dozens of experiments with rodents trying to theorize what would happen during population expansion with perfect external conditions, the two that yielded most ample results to back his behavioral sink theory were Rat City (1958-1962) and Mouse Utopia (1968-1972). 

The Rat City experiment consisted of a dozen rats being put into a controlled environment with perfect living conditions, Calhoun recording their reproduction rate over the course of four years as they developed and grew as an independent society. Despite the perfect living conditions and the pen’s opportunity for them to reach over 2,000 members, the population never exceeded 200 and the entire society exhibited extreme mental decline before they all began to die off. This experiment is how Calhoun began developing his theories about “behavioral sink” regarding the affect population density and crowding can have on behaviors and instincts.

“Perfect” External conditions

  • Unlimited food and water 
  • Unlimited nesting material 
  • Secluded pens for rodents to build their family nests 
  • Zero predators
  • Climate control 

In need of more data, Mouse Utopia was a near replica to Rat City, the few differences being the change in rodent type and a few adjustments to the structure of the pen. In the beginning, Mouse Utopia showed great promise, with the population steadily rising from 8 up to 2,200 members over the course of the experiment. However, the mice of Mouse Utopia met the same fate as the rats of Rat City, eventually showing extreme deterioration of instincts and behavior as the society stopped reproducing and dwindled off into nothing. 

How Population Density and Overcrowding Can Impact A Society Long-Term 

Now, let’s refer back to our human frat party scenario in relation to Mouse Utopia. Much like the college party, Mouse Utopia began with 8 original mice creating their society. The men established dominance as alpha males and came first in the social hierarchy, giving them much power and dictation, much like a host of a party would have. The new mice that were born into the society, aka the guests of a party, would exclusively stick together with their families in their designated areas of the pen. Alpha males would prevent outside males from mating or interacting with the females of their family. Mice that were neglected by their mother’s or rejected by the alpha males would withdraw from society and isolate themselves, much like an outsider would do at a party where they have no friends. The more mice that joined the population, the more they began to crowd together in the same main areas, typical to a human party where everyone gathers on the dancefloor. 

Even though there was enough space for all the mice to spread out and peacefully live amongst each other, they continued to overcrowd. Mice would become agitated and stressed from the overcrowding and get into fights with each other, lashing out without causation. The larger the population grew, the more agitated the mice became mentally, the overcrowding of their peers causing deep mental distress. This led to an evident behavioral sink. 

Examples of A Behavioral Sink Observed In Mouse Utopia 

  • Infant immortality, loss of maternal instincts 
  • Undeveloped adults due to mothers neglecting and abandoning young
  • Cannibalism despite unlimited resources, mice eating the young
  • Overcrowding, unable to eat or drink without the presence of others, overcrowding one area of the pen despite ample room to fit everyone if they were to spread out 
  • Aggression, becoming stressed at overcrowding and lashing out at others 
  • Sexual deviance, males trying to mate with other males, males ganging up on females and forcing them to mate 
  • Complete isolation, younger mice isolating themselves from society and living in the outskirts of the pen with zero social interaction 
Mouse Utopia Village
Mouse Utopia Village

Why do population density and overcrowding lead to a behavioral sink? 

Population density and overcrowding lead to a behavioral sink because of the mental stress that constantly being around others causes. Company is good in small doses, but when everyone tends to flock towards the same regions daily, it becomes overwhelming and exhausting. For the rodents in Calhoun’s experiments, what they experienced would be the equivalent of us having to walk through a crowded theme park every time we needed to eat or drink. With exponential population growth, it would only take so long before someone would snap. 

Moreover, even though some individuals may handle crowds better than others, their natural responses are only as strong as the weakest in the society. All it takes is one person losing their normal behavioral instincts to negatively impact everyone else’s cognitive responses in a chain reaction. We saw this happen a lot throughout Calhoun’s experiments in several instances in which members of society lost their ability to normally function:

  • Alpha males would grow tired of defending their pack from new young and eventually give into their exhaustion
  • Pregnant mothers would have to protect themselves and their young alone 
  • Mothers would become easily stressed or aggravated because of their constant flight or fight protective mode, therefore lashing out on their newborns 
  • Newborns would be abandoned by their mothers and left to fend for themselves, often dying or being cannibalised by other adult mice 
  • Newborns who actually survived this neglectful upbringing were mentally slow and intelligent, lacking any social skills and therefore unable to properly behave around the rest of society 

Do Calhoun’s Experiments Reflect The Human Experience? 

While the recordings of a behavioral sink amongst rodents experiencing population density is an interesting phenomenon, it seemingly has no direct correlation to mankind. While we too experience the stress and inhibilitation of overcrowding in various areas of the world, as a society we are much more advanced than rodents could ever be. We have morals, laws that dictate our land, and worldwide communication that would prevent our society as a whole from spiraling into the same doomsday that Mouse Utopia did. Giving Calhoun’s experiments an application to real world examples only supplies a better comprehension of what went on within these rodent societies, and where they went wrong.

However, my personal perspectives, especially given the events of 2020, I find it difficult to argue there are not human parallels. Though I am not a any sort of accredited scientist, many of these behaviors are being being witnessed in humans of today.

I can’t help but to compare it to the notion that human’s are beasts of burden. Dr. Jordan Peterson often says “Pick up your damn cross!”, which I understand as, as much as most people despise work, we suffer emotionally when we lead a life with no pressure. We are created to produce. When we are not producing, we are not happy. Of course there is the dichotomy…all we want to do is win the lottery, sit on the beach and drink margaritas. But the reality is that we would soon become miserable.

We often see this exhibited in the ultra-wealthy. People that seem to have not a care in the world, yet they are miserable, even suicidal.

The biggest scientific argument against this paralleling with humans is that humans have “agency”. Meaning, we do not have a great big hand that reaches in to feed us, move us and ultimately control us…though I believe this can be easily argued.

Just like the rats and mice, we seem to fail to understand that there is a glass ceiling on our population. So many are concerned about overpopulation without knowing that there is a built in “governor” that sees that we do not become overpopulated. And even when food, shelter and all other resources are provided, that governor breaks us down mentally, then socially and we can no longer recover from the downward population spiral.

I guess time will tell…

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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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