12/2/2023 0 Comments Mouse utopia experiment reportMoreover, these mice were noted to be unintelligent compared to previous generations. This generation, for all the emphasis they placed on grooming, would not reproduce. Newer generations born in the now dysfunctional mouse utopia became withdrawn, spending their days grooming obsessively and dedicating their time solely to eating, drinking and sleeping. “…In the experiments in which the behavioural sink developed, infant mortality ran as high as 96 percent among the most disoriented groups in the population.” – John Calhoun As a result extreme population densities developed in the pen adopted for eating, leaving the others with sparse populations.” Individual mice would rarely eat except in the company of other mice. As many as 60 of the 80 mice in each experimental population would assemble in one pen during periods of feeding. The animals would crowd together in greatest number in one of the four interconnecting pens in which the colony was maintained. “The common source of these disturbances became most dramatically apparent in the populations of our first series of three experiments, in which we observed the development of what we called a behavioural sink. The social organisation of the animals showed equal disruption…” Amongst the males the behaviour disturbances ranged from sexual deviation to cannibalism and from frenetic over-activity to a pathological withdrawal from which individuals would emerge to eat, drink and move about only when other members of the community were asleep. An even greater number, after successfully giving birth, fell short in their maternal functions. “Many were unable to carry pregnancy to full term, or to survive delivery of their litters if they did. Some males became repeated targets of attacks.Ĭalhoun had noted during his experiments: Males fought each other for acceptance, those that where defeated withdrew. The mice showed different types of social dysfunctions. He noted that the new generations were inhibited since most space was already socially defined. During the third phase Calhoun observed the collapse of the mice civilisation. During this phase, the mice population peaked at 2200 individuals, although there was space for 3000. The third phase was named the ”equilibrium phase”. It was also observed that some units started to become crowded. The second stage was named the ”exploit period”. During this stage the mice population exploded. Calhoun observed that some compartments became more populated than others, and therefore some units used more resources. He noted down behavioural changes and population numbers. He found that there were four distinct phases of population change observed during the experiment. The first stage, named “Strive”, was a phase in which the mice explored and adjusted to their new habitat, set territories and created nests. Upon verifying that they were healthy they were introduced into the enclosure.Ĭalhoun observed the mice population over the course of the experiment. By removing the risk of predation, the mice could grow in an environment free from external stress. The room was then compartmentalised into different units, this allowed Calhoun to identify how different social groupings formed.įour pairs of mice were screened for diseases (four male and four female). The room was closed off so that neither the mice could get out nor predators get in. This was achieved by fitting a pen (box-shaped enclosure) with unlimited food and water. His team created a comfortable environment ideal for the mice. John Calhoun’s experiments gained world-wide recognition and his expertise was sought after by government bodies such as NASA. They present a useful yet grim insight into what could be our own future, for no matter how many times Calhoun repeated the experiment, the results led to the same inevitable conclusion: extinction. The social decay led to unrest in the environment, which in turn led to sub replacement fertility. It was concluded that nature has a limit in which social animals can interact. He chose rodents as these reproduce rapidly thus allowing him to observe the development of several generations of mice in a relatively short space of time.Ĭalhoun and his researchers found that in a space-limited/resource unlimited environment, the population of mice would explode peak-out and then collapse to extinction. This test was replicated several times and it was found that these led to the same outcome each time. The reason for this phenomenon was found to derived from social decay which worsened with each generation. In 1950, an American ethologist named John Calhoun created a series of experiments to test the effects of overpopulation on the behaviour of social animals. The animals which Calhoun chose for his experiments where mice (and later on rats).
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