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When populations reach tipping point
Time to revisit Calhoun’s rat and mice experiments
When John Calhoun started performing experiments on rats and mice to determine effect of population density on behaviour, he little imagined the horrifying outcomes that today are looking a little too familiar. Only today these are beginning to appear in the human population and we should recognise them as markers of a deeper problem.
In the 1960s, Calhoun built a “rat city” where everything was provided to keep a rat happy, except space. It provided limitless food and water, perfect heating and all of life’s comforts, a kind of rat utopia.. The result was a population explosion leading to chronic overcrowding, extreme behaviours and finally extinction. Long before the rats had reached maximum population density, as predicted by Calhoun, they began to display a range of “deviant” behaviours: mothers neglected their young; dominant males became increasingly aggressive; subordinate rats withdrew psychologically; while others became hypersexual. It even reached the stage where the living cannibalised the dead.
Further experiments were conducted, this time with mice, to confirm these findings, only to be met with even more extreme behaviours.
Esther Inglis-Arkwell wrote about Calhoun’s twenty-fifth habitat experiment:
