However, the behavioral sink was not the outcome of all experiments, e.g. The experiments that resulted in such a behavioral sink ended in the extinction of the colony, due to all males and females having become uninterested in reproduction. With the lack of territory normally established by males, the females also reproduced less, neglected their offspring and cared for their offspring on their own, partly overtaking male tasks of maintaining territory and demonstrating aggression.
Males engaged in sporadic acts of violence. Some male rodents also formed marauding gangs, attacking any female and young rodents that they came into proximity with. These "brood pens", exhibited the highest infant survival rate. Calhoun stated that this was due to the estrous females in such pens being protected from incessant and unwanted attention from the lower status males, particularly the hypersexual "probers" who obsessively stalked and approached any estrous female they could find, despite being repeatedly defeated and driven away by the dominant rodents. In some end pens, where dominant rodents maintained harems, the female rodents often exhibited healthy nurturing behaviors, feeding, nesting and protecting their young from harm.
The few dominant rodents that remained, monopolized almost all breeding opportunities with the remaining females, maintaining harems by chasing away any lesser male who attempted to approach their territory, apart from a few subordinate males, who never attempted to mount the females in the dominant rodent's harem, and were therefore permitted to approach. They lost social functioning, and did not have sex. Within these apartments were what Calhoun deemed the "beautiful ones", or those who engaged in only grooming, sleeping, and eating. Aggressive territorial males guarded the entrances to the "apartments". Those male and female mice lucky enough to secure long-term non-crowded territory were guarded in "apartments" with small entrances. Some rodentcels alternatively became hypersexual, and either engaged in homosexual behaviors or incessantly chased female rodents in estrous (dubbed probers by Calhoun), in spite of being defeated and chased away by the dominant rodents. Those dubbed "dropouts", who had ceased doing any sort of useful social activity, but remained in the center, engaged in frequent "pointless violence". They often found neglected and dead young lying in the nests, which they frequently cannibalized. Some managed to follow the females into their burrows, eschewing the typical courtship rituals rodents engage in (intermittently poking their heads into the female's burrow until she accepts his advances). This was primarily caused by male animals failing to claim territories of significant size, thus failing to claim dominance status and thus constantly engaging in fights. In one of his experiments which was later once reproduced, the animals abruptly reproduced less and showed unhealthy social behavior after 1.7 years of rapid population growth. In Calhoun's experiments, rodent populations were kept in artificial, small environments with otherwise ideal conditions and unlimited food supply. īehavioral sinks in Calhoun's experiments are thought to have been caused by evolutionary mismatches caused by overpopulation or the relaxation of natural selection in these 'utopian' conditions inevitably leading to the build-up of deleterious mutations among the mice that ultimately had the effect of reducing both group and individual fitness (see social epistasis amplification model).ĭescription of the experiments He claimed the ensuing physiological strain this harsh competition for limited social roles put on the mice subjected to these conditions resulted in the emergence of "autistic-like creatures, capable only of the most simple behaviours compatible with physiological survival", eventually leading to the "breakdown of all normal social behavior", with this often resulting in the auto-extinction of the rodent colonies in question.
UNIVERSE 74 RAT UTOPIA SERIES
Ĭalhoun conducted a series of experiments with mice and rats which are called mice/rats utopia or paradise, some of which resulted in such population collapses.Ĭalhoun's explanation for the outcome of his experiments was that overpopulation leads to social hierarchies where there was more demand for social roles than could be reasonably filled. Calhoun, referring to an abrupt population collapse in extremely mild environments. The behavioral sink is a term coined by American behavioral researcher John B. Calhoun in one of his experimental colonies
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