What Humans Can Learn From Calhoun's Rodent Utopia
Between 1968 and 1970, American ethologist John B. Calhoun (1917-1995) conducted a behavioral study of captive mice within a nine-square-foot enclosure at a rural facility in Poolesville, Maryland. Within the enclosure known as Universe 25, several pairs of mice bred a population, which ultimately swelled to 2,200. Eventually, they established social orders that created inside and outside factions, and soon mating ceased altogether.
The study confirmed his grim hypothesis, based on earlier studies of the Norway rat in small settings. In his theory he suggested that overpopulation spawns a breakdown in social functions. That, in turn, inevitably leads to extinction.
Though wildly controversial when first made public, Calhoun's theory has raised concern over the years that the social breakdown of Universe 25 could ultimately serve as a metaphor for the trajectory of the human race. Consequently, the “rodent utopia project” has been a subject of interest among architects, city planning councils and government agencies around the world.
Early Rodent Studies
Calhoun began his experimental research on rodents in 1947, when he studied an enclosed group of Norway rats at a barn in Rockville, Maryland. Supplying the critters with unlimited food and water, he expected to see their population swell to 5,000 over the course of the 28-month experiment. However, the population capped out at 200 after subdividing into smaller groups, each of which comprised merely a dozen individuals.
Continuing with these studies during the 1950s, Calhoun set up a more complex enclosure to examine how further groups of rodents would behave in a sterilized, predator-free environment. Over the course of these experiments, the same sequence of events would transpire each time:
• The mice would meet, mate and breed in large quantities.
• Eventually a leveling-off would occur.
• After that, the rodents would develop either hostile and cliquish or passive and anti-social behaviors.
• The population would trail off to extinction.
In 1962, Scientific American published Calhoun's observations from his research in the article "Population Density and Social Pathology," wherein he coined the phrase "behavior sink" to describe the results of overcrowding — namely the breakdown of social functions and the collapse of populations — in the enclosed rodent environment. Hitting the public just as vast urban expansion saw growing numbers of college grads flocking to big cities for work opportunities, many viewed the article as a warning of what could happen to the human race if populations continued to rise at their current rate.
Universe 25: Calhoun's Experiment With A Rodent Utopia
Expanding on his earlier studies, Calhoun devised his ultimate research experiment. In Universe 25, a population of mice would grow within a 2.7-square-meter enclosure consisting of four pens, 256 living compartments and 16 burrows that led to food and water supplies.
With a plague-free environment, a plenitude of comforts, a lack of predation and an unlimited supply of consumables, the mice would enjoy all the luxuries equivalent to modern human life. Calhoun initiated the experiment with four pairs of healthy mice, which were set loose into the enclosure to begin the new society.
During the first 104 days — a phase Calhoun dubbed the "strive period" — the mice adjusted to their new surroundings, marked their territory and began nesting. This was followed by the "exploit period," which saw the population double every 55 days. By the 315th day, Universe 25 contained 620 mice.
Despite the abundance of space throughout the enclosure — each compartment could house up to 15 individuals, and the overall enclosure was built for a capacity of 3,000 — most mice were crowding select areas and eating from the same food sources. The act of eating, as it turned out, came to be viewed as a communal activity, which caused most of the mice to favor the same few compartments.
All of this huddling, however, led to a drop in mating, and the birthrate soon fell to a third of its former level. A social imbalance also took place among the mice:
• One-third emerged as socially dominant.
• The other two-thirds turned out less socially adept than their forbearers.
• As bonding skills diminished among the mice, Universe 25 went into a slow but irreversible decline.
Social Status in Universe 25
By Day 315, behavior disparities between males of high and low status became more pronounced. Those at the bottom of the pecking order found themselves spurned from females and withdrew from mating altogether. Having no roles to fulfill within the society of mice, these outcast males wandered apart from the larger groups to eat and sleep alone — and sometimes fight among one another.
The alpha males, by contrast, became more aggressive and pugnacious, often launching into violence with no clear provocation or motive. At times, these males would roam around and