The Calhoun Experiment: From Rodent Utopia to Absolute Nightmare

What would be the equivalent of perfection for a group of mice? As mammals like us, it's not hard to set basic parameters: a safe and clean space, abundant food and water, no natural predators, and disease control. Researcher John B. Calhoun offered exactly that through a series of experiments that began in 1947. The only limiting factor for the mice was physical space, and despite all the initial advantages, they ended in a general collapse. Why?

Malthusian catastrophe, Soylent Green, Thanos snapping his fingers. This isn't the first time we've explored the concept of overpopulation under different conditions. The idea of a disturbing future without food or safe water, trapped in a constant war for space and basic resources, has never been fully banished. Some believe that future is inevitable. Others think we still have time to correct course, and then there are those who think it will never happen.

These differences are what lead us to investigate further, but overpopulation studies are nothing new. In fact, the most advanced were conducted between the late '40s and early '70s, and they share a common name: John B. Calhoun, father of the behavioral sink, an expression he developed between 1958 and 1962, after having conducted experiments with Norwegian rats.

The Mouse Utopia

The experiments were based on utopias, enclosed spaces with virtually ideal conditions for the proliferation and reproduction of rodents. Unlimited food and water were guaranteed, as well as nesting material, absence of predators (cats, owls, etc.), and disease control. The most famous of these experiments, called Universe 25, only confirmed everything Calhoun had seen up to that point.

Universe 25 began with just eight mice, four males and four females. By day 560 of the experiment, the population had reached 2,200 individuals. From that point on, the fate of Universe 25 was sealed. The only destiny for its inhabitants was extinction, even though the maximum capacity of the universe was calculated at 3,000. Every moment of their lives was spent in the company of other mice. Few females managed to carry their pregnancies to term, and most seemed to forget their offspring, abandoned halfway.

The Beautiful Ones

The few isolated spaces remaining were home to a group of mice that Calhoun called the beautiful ones. Guarded by an alpha male, the females and the few males present discarded any desire to mate, fight, or compete. They simply limited themselves to eating, sleeping, and grooming. Those beautiful ones managed to escape death and madness in other regions of Universe 25, but the price to pay was the loss of all basic social behavior. In Calhoun's own words, almost autistic creatures, with dead spirits.

Universe 25 continues to capture our attention even after so many years, but the conclusions have varied since then. At first it was a compelling example of a Malthusian nightmare, the breeding ground for a behavioral sink that inevitably leads to the collapse of society. However, more recent studies propose another kind of conclusion.

Rethinking the Conclusions

The spaces for the mice in each of the available corridors had a single entrance and exit, that is, they were very easy positions to defend. The most territorial males thus managed to reduce the number of individuals in each space (the beautiful ones that remained isolated), triggering overpopulation in the rest of Universe 25. In other words, the problem would not be overpopulation, but a failure in resource distribution.

Finally, there is a third position. Another researcher, Jonathan Freedman, focused his efforts on high school and college students, and his conclusion is that collapse is not associated with density, but with an excess of social interaction. Not all of Calhoun's mice ended up crazy or violent, and the key was that they managed to isolate themselves from the rest...

Sources

Sources: Smithsonian, io9, National Library of Medicine