Violent encounters sometimes ended in mouse-on-mouse cannibalism.ĭespite – or perhaps because – their every need was being catered for, mothers would abandon their young or merely just forget about them entirely, leaving them to fend for themselves. The 'alpha male' mice became extremely aggressive, attacking others with no motivation or gain for themselves, and regularly raped both males and females. The breakdown of usual mouse behavior wasn't just limited to the outsiders. Due to this they had excellent fur coats, and were dubbed, somewhat disconcertingly, the 'beautiful ones'. The female counterparts of these isolated males withdrew as well. Some mice spent their days preening themselves, shunning mating, and never engaging in fighting.

Later on, they would attack others in the same pattern. The withdrawn males would not respond during attacks, lying there immobile. 'Even so, they became characterized by many wounds and much scar tissue as a result of attacks by other withdrawn males.' From this point on they no longer initiated interaction with their established associates, nor did their behavior elicit attack by territorial males,' read the paper. 'Males who failed withdrew physically and psychologically they became very inactive and aggregated in large pools near the center of the floor of the universe. The mice that found themself with no social role to fill – there are only so many head mouse roles, and the utopia was in no need of a Ratatouille-esque chef – became isolated. Here, the 'excess' could not emigrate, for there was nowhere else to go. 'The excess that find no social niches emigrate.' 'In the normal course of events in a natural ecological setting somewhat more young survive to maturity than are necessary to replace their dying or senescent established associates,' Calhoun wrote in 1972. The mice split off into groups, and those that could not find a role in these groups found themselves with nowhere to go. When the population hit 620, that slowed to doubling around every 145 days, as the mouse society began to hit problems. About every 55 days, the population doubled as the mice filled the most desirable space within the pen, where access to the food tunnels was of ease.

The experiment began, and as you'd expect, the mice used the time that would usually be wasted in foraging for food and shelter for having excessive amounts of sexual intercourse. It's not often something is described as a 'utopia, but also there were lions there picking us all off one by one'. Both these things seem to be beyond mouse brains.As well as this, no predators were present in the utopia, which sort of stands to reason. The main reasons why we have not descended into intra-tribe violence once we started to live in permanent settlements and larger villages are probably social innovations as well as recognizing and sharing the benefits of larger scale village structures. If primitive hunter gatherers grew beyond that limit it would result in the exodus of some part of that population into a new group that went elsewhere, probably mainly to retain group cohesion but in part also because the resources needed for survival at any one place were limited. This would be analogous to humans having the mental capacity to keep up relations with something like 150 to 300 people. But with nowhere to go the mice created smaller subgroups that couldn't go anywhere yet still tried to maintain their own territory, mates etc. in the enclosure) and in nature this would usually result in a non-violent split of the population into two groups that go their own way.

Possible explanation: After a certain point of population growth the mice cannot keep track of all the individuals in their group (i.e.

Youtube mouse utopia experiment