The Rat Utopian that Collapsed because of Overpopulation

"Behavioral sink" is a term invented by ethologist John B. Calhoun to describe a collapse in behavior that can result from overpopulation. “The Rat utopian experiment” or as Calhoun called it “Universe 25” conducted by psychologist John B. Calhoun in 1972. The expirement involved creating a utopian environment for a population of rats. The enclosure provided an abundance of food, water, nesting materials, as well as ample space for rats to roam and socialize.

Initially the rat population thrived and their numbers increased rapidly.

However, as the rat population grew, social problems began to emerge. The Rats became increasingly aggressive, territorial, antisocial. Females began to abandon their offsprings, young rats began excessively grooming and self amputated.

The collapse of the rat utopia was attributed to the breakdown of social structures and the inability of the rats to cope with the overcrowded conditions. Calhoun observed that the rats had become "socially pathological" and speculated that similar dynamics may potentially occur in human societies under certain conditions.