As we drove back to Pagosa Springs from Durango on Friday, I told my friend Glenn about an editorial series I was planning to write, about the rats of NIMH — a series of rodent experiments in population density and animal behavior led by scientist and ecologist Dr. John Calhoun.
The results of those experiments suggested, to Dr. Calhoun, a dystopian future for humankind. But they also suggest, to me, that Mother Nature has ways of controlling out-of-control growth… ways we may not even be aware of.
Since 2004, we’ve been covering, here in the Daily Post, various issues related to growth in Archuleta County. My recent research into the rats of NIMH has suggested some explanations for why America finds itself in its current situation… and perhaps, for what’s been happening in Archuleta County… as we approach the November 2024 election.
Yesterday, in Part One, I gave a quick summary of an experiment carried out by Dr. Calhoun back in the late 1940s in Towson, Maryland, focused on Norway rats. A decade later, Dr. Calhoun obtained funding from the National Institute of Mental Health (NIHM) to continue his experiments with rodent populations.
This was back in the day, before the term “mental health” began appearing in the national media on a daily basis. Back when mental health was rarely talked about, in fact.
Dr. Calhoun’s work with NIMH mainly involved mice, rather than rats… living in enclosed spaces with essentially unlimited food and water.
In one such experiment, Dr. Calhoun introduced four pair of mice into a metal enclosure designed to accommodate 3,800 mice, in terms of nesting space. Wire mesh tunnels gave access to nesting boxes, food hoppers, and water dispensers. There was no shortage of food or water, or nesting material. There were no predators.
The only adversity was the limit on space.
Here’s a rather dark and disturbing description of the experiment, from Wikipedia:
Initially, the population grew rapidly, doubling every 55 days. The population reached 620 by day 315, after which the population growth dropped markedly, doubling only every 145 days. The last surviving birth was on day 600, bringing the total population to a mere 2,200 mice, even though the experiment setup allowed for as many as 3840 mice in terms of nesting space.
This period between day 315 and day 600 saw a breakdown in social structure and in normal social behavior. Among the aberrations in behavior were the following: expulsion of young before weaning was complete, wounding of young, increase in homosexual behavior, inability of dominant males to maintain the defense of their territory, aggressive behavior by females, passivity of non-dominant males with increased attacks on each other which were not defended against.
After day 600, the social breakdown continued and the population declined toward extinction. During this period females ceased to reproduce. Their male counterparts withdrew completely, never engaging in courtship or fighting and only engaging in tasks that were essential to their health. They ate, drank, slept, and groomed themselves – all solitary pursuits. Sleek, healthy coats and an absence of scars characterized these males. They were dubbed “the beautiful ones”.
Breeding never resumed and behavior patterns were permanently changed.
Conclusions drawn from this experiment by Dr. Calhoun:
When all available space is taken and all social roles filled, competition and the stresses experienced by the individuals will result in a total breakdown in complex social behaviors, ultimately resulting in the demise of the population.
He labeled this dystopian breakdown as a “behavioral sink.”
Around the time that Dr. Calhoun was experimenting with rodents, social scientists in America were looking at exponential global population growth, and issuing dire warnings about the future of humankind.
In 1960, the magazine Science published a paper by scientists Heinz von Foerster, P. M. Mora and L. W. Amiot, predicting that on November 13, 2026, the “human population will approach infinity if it grows as it has grown in the last two millennia.”
It so happens that November 13, 2026 is a Friday.
Just a few years after this doomsday alarm was issued, the annual growth of global population peaked at about 2.1% and began to decline. By 2020, the growth rate stood at just a bit more than 1%, the result of a steadily declining Total Fertility Rate (TFR) — the number of children born to a woman during her reproductive period.
A TFR above 2 is generally assumed to be necessary to maintain a steady human population.
Some political leaders have, in recent months, been issuing warnings about declining fertility, and about American women not having enough babies. Some of these same politicians have also complained about same-sex marriage, gender-transition therapies, a crisis around male masculinity, increasing social isolation, random gun violence, and mental health issues in general.
To my overactive imagination, these recent developments in modern human society seem eerily similar to the social breakdown Dr. Calhoun observed in his artificial rodent environments in the 1960s.
Mother Nature, at work once again?
In his earlier experiments with Norway rats, during the late 1940s, Dr. Calhoun determined that the largest number of rats that could live peacefully as a family clan was about 15. He also determined that, within an enclosed environment, a rat population would naturally stabilize at about ten clans. So about 150 rats.
In his later experiments with mice, in a particular “enclosed space”, the limit appeared to be closer to 2,000 mice. But that number ultimately led to social dysfunction and population decline.
For those of us fortunate enough to live in Pagosa Springs, the “space” does not seem “enclosed” to even the slightest degree. Everywhere we look are vast meadows, rolling hills, and majestic mountains.
But I’m still plagued by the idea that any environment — rat, human or otherwise — has an optimum population limit, and that unbridled population growth will eventually lead to unpleasant social outcomes.
It’s possible that Archuleta County is nowhere near that limit. But how would we know?
Read Part Three… tomorrow…