Overpopulated Mouse Colony Perishes

Status: A hoax (perhaps?) based on a real experiment
Henry Rosenbaum emailed me with the following description of a hoax, followed by a question:

For 30 years, from the mid-1960's, I lived in central Michigan, about a four hour drive from Toronto, Ontario, Canada, where my wife and I often visited for weekends. I well recall an exhibit at one of the major museums that featured an enclosed cage/environment with a number of mice and a descriptive explanation to the effect: The mice were limited in the amount of space they were afforded, yet they were provided all the food and water their colony required, regardless of its numbers. The display stated they had at first healthily thrived and multiplied but as their supported numbers greatly increased without any increase in territory, the members became first combative and then homosexual, with the ultimate dying out of the colony despite the unlimited physical resources. Of course this was to illustrate what (perhaps as Malthus had predicted?) would ultimately happen to man if population growth was not checked.

I believed it was shortly after I left Michigan (mid-1990s) that I read in a West Coast newspaper that the museum had acknowledged the exhibit was a hoax made up in the minds of its (two, as I recall) researchers. I neglected then to clip the article and have for the last couple of years been unsuccessfully trying to re-locate the information of the hoax and its details. I had hoped it might be mentioned in your book and then attempted to research your web site under both mice and rats with variations as well as under several subject matters, all without success. I would appreciate if you could point me in the right direction.

I had never heard of this experiment/museum exhibit before (which is why it's neither in my book or on the site). Does it ring a bell with anyone?


Posted on Sat Feb 25, 2006


But why would the entire colony die? Once enough of them died to reestablish equalibrium the rest would carry on and probably, eventually overpopulate again, and the cycle continues. Unless the theory here is that overpopulation makes everyone gay, so there is no offspring. But then how do you explain Los Angeles.....oh wait.....hmm maybe they are right.
Posted by Lonewatchman  on  Sat Feb 25, 2006  at  07:43 PM
I heard this expirement referenced loosely in a book I've recently read, The Story of B, although I don're remember hearing about the entire colony dying out. The idea was that the amount of food available and the population are always proportional. This is a fundamental law of ecology, so even if the expirement was fake I doubt that law is.
Posted by Citizen Premier  on  Sat Feb 25, 2006  at  08:20 PM
I'm a google-ninja but searching around for this was insane. Never try to use the keyword "homosexuality" in relation to science. It'll scare you. Anyway, I think I found what this guy is looking for.

There is a paper by John B Calhoun called "Population Density and Social Pathology." (Calhoun, John B. 1962.
Posted by Kelly  on  Sat Feb 25, 2006  at  08:39 PM
Nice find, Kelly. So Calhoun's 1962 experiment is real. But I guess the exhibit in the Toronto museum could have been fake. Though why would the museum bother to fake that, unless they didn't have the stomach for torturing mice.
Posted by The Curator  in  San Diego  on  Sat Feb 25, 2006  at  09:13 PM
Calhoun's experiment with rats (not mice) is described fairly well in John Bleibtreu's "The Parable of the Beast". He was wanting to study how their social structure might be dependent on access to the communal burrow, and constructed two types of burrow with different access; however he soon saw that things were going wrong in both, and the experiment was not what he'd planned.

Each burrow contained lines of 4 pens in a row, with openings between so that rats could pass from pen #1 to #4, by passing through #2 and #3 in between. Each pen had food, water and nesting material; but gradually pens #2 and #3 in each row became the centre of social activity, regardless of resources, simply because they were in the middle.

Things went further wrong when it was found that the subdominant rats matured earlier than the dominant males. This meant that the subdominant ones left the end pens early, leaving the dominant males with no-one to fight. These males in the end pens thus became even more aggressive and territorial, so increasing the crowding in the middle pens - even though, as at the start, there was plenty of room, food etc. for all of them.

The crowding in the middle pens induced fighting, aberrant sexual behaviour (meaning anything untypical, not necessarily homosexual), random violence, intrusion on lactating females, various health problems, disrupted behaviour patterns, and neglect of young.

The "mice in the museum" exhibit sounds interesting; perhaps they were trying to reconstruct Calhoun's experiment, or do a variation on it? The whole issue of overcrowding with any social species (such as rats in pens, or humans in slums) is about more than just space.
Posted by Wendy  on  Sat Feb 25, 2006  at  09:44 PM
I just had a thought: maybe the "museum mice" hoax was that the researchers were claiming something not suggested or supported by the experiment; e.g. that overcrowding causes homosexuality and then extinction, or that crowding is solely dependent on space available rather than a range of factors (arrangement of space, access points, privacy for nesting mothers, relations between different-ranked animals etc).
Posted by Wendy  on  Sat Feb 25, 2006  at  11:03 PM
I am amused by the google ads for this post. 😛
Posted by Kelly  on  Sat Feb 25, 2006  at  11:11 PM
Lonewatchman, you da man!!! But mine was gonna be "How do you explain San Francisco?"...
Posted by Christopher in Joplin, Missouri  on  Sun Feb 26, 2006  at  06:31 AM
Long ago, as an undergrad biologist I wrote a review of John Calhoun's experiment for a tutor from a 'science and policy' research group. I covered Calhoun's experiment and its observations, reported that similar (but not identical) experiments on UK rodents had instead noticed a gradual decline in births as space become more limiting, posited that if the situations were shown to be equivolent then perhaps british rodents might have adapted their behavious to island life, and finished with a comprehensive warning on inferring to much about human populations from a study on rats. By the end, I was quite proud of it.

When I got it back there was only one comment on the whole paper. The tutor had objected to me describing the observed homosexual behaviour as 'abnormal'.
Posted by David B.  on  Sun Feb 26, 2006  at  04:00 PM
Here's an abstract of the Calhoun paper:

Posted by intjudo  on  Sun Feb 26, 2006  at  05:50 PM
This is not a hoax. This really happens. When I was 17-18, I had some gerbils that my Sister didn't want anymore. I kept them in a Hartz setup (the one with all the tubes for them to run around in - mine was set on top of another aquarium with a tube leading down - so basically 2 tanks in1) I started with 2 and they bred to 8 I think. After the babies became adults, I expanded their habitat with another of the same setup and connected it to the first one. It really was pretty sweet. They had lots of room. Well one thing lead to another and they doubled to about 16+. They seemed fine until one night, for no reason every single one went cannibalistic and they litterally tore each other to pieces. I never understood why. They had plenty of food and water and I've seen way more gerbils than 16 in one tank at the local pet store. I never saw any turn homosexual -they may have but how do you tell the males from females anyway? So there you have it, the truth of the great gerbil massacre of 1992.
Posted by Cerebulon  on  Sun Feb 26, 2006  at  10:02 PM
Oh, sorry. I need an PS to my first post. There were about 3 left after the massacre - I took them out and put them into a new setup but they wouldn't eat and wouldn't drink. They lasted about 3-4 days afterwards but all eventually just died. They would just sit in corners of the tank in little curled up balls and shake constantly. It really was very sad. After the survivors died, I just threw everything away. All the tanks were covered in blood and cedar chips. I've never owned a rodent since! I stick to reptiles - at least they never do stuff like this.
Posted by Cerebulon  on  Sun Feb 26, 2006  at  10:10 PM
That is a great story. No particularly pleasant, but interesting.

I wonder about the genetic quality of rodents raised in captivity. They are descended from the ones that weren't smart enough to get away.
Posted by skeptictank  on  Mon Feb 27, 2006  at  07:29 PM
As a person who has kept rodents as pets for quite some time (guinea pigs, hamsters, and lots of mice), I can explain what happened to Cerebulon's gerbils by citing two facts which are widely known by rodent fanciers:

1. Inbreeding can cause serious mental and behavioural aberrations in rodents. (And it only takes about two generations for the aberrations to surface)

2. Inexperienced mothers will frequently kill and eat their first litter. Experienced mothers will frequently kill and eat their babies if something is wrong with them--if they are underweight, retarded, insane, or too sickly or malformed to live (all conditions which could easily be caused by inbreeding). And they can sense these problems in their babies easily and quickly.

You had a tank full of gerbils of both sexes all descended from one pair, dude. Your experience does not bear out the Calhoun experiment; it merely bears out the practice of segregating males from females, and especially if they are closely related.

It may also be worth noting that rodents who are advanced in age can readily go senile (holes actually form in their little cerebellums) and engage in some very disturbing behavior. It's quite common. I once had a five-year-old hamster--very old for a hamster--who started going in circles continually in his last days, eventually catching his little hind leg in his wheel and continuing to circle until he had twisted it off. After I freed him, he continued to limp in circles all night, and died the next day.
Posted by Barghest  on  Wed Mar 01, 2006  at  03:23 AM
David B. wrote

"if the situations were shown to be equivolent"

I just needed to express my admiration of that pun, since noone else saw fit to.
Posted by Shawn Crahan  on  Wed Mar 01, 2006  at  09:38 PM
I believe this is true. I remember very clearly a few years ago in school watching a very old looking movie clip showing a colony of mice like what you describe. I think that in the movie they became violent and began even killing their young. I do not remember the homosexual part though. This was shown to middle school students about the idea of maximun population thresh hold for an area.
Posted by student  on  Fri Mar 03, 2006  at  08:22 PM
Well, mouse colony is what Amazon thought this was. Here is a book on the subject. Inbreeding may indeed have been a large factor. But many of the social issues we face today seem to be based in largely overcrowded areas of the country.

Posted by Tecnopaul  on  Wed Nov 29, 2006  at  10:46 PM
The Calhoun study was real. Henry Rosenbaum's email contains the accuracy of the situation: "the museum had acknowledged the exhibit was a hoax made up in the minds of its (two, as I recall) researchers." The exhibit was indeed a hoax. It was not a real experiment. They put up a display with mice in a cage, and used Calhoun's results as the basis for their description. No such conditions were placed on the mice in the exhibit. Had they been, and it had been placed on display, they'd have almost certainly been cited for animal abuse. What you could do with experimental animals in 1962 and mid-1990's was very different, especially in such a public venue. For the same reason it is highly unlikely any recent replications exist.

There is an answer to Christopher from Joplin's (hopefully) humorous question "How do you explain San Fransisco?" It was the major demobilization point for the Pacific theater after WW II. Many who could not or preferred not to go home after discharge stayed there. Among the group that "could not or preferred not to" were homosexuals, who found San Fransisco's very liberal attitude towards all manner of differences (some of those considered improper if not illegal elsewhere) to be hospitable. The fewer homosexuals who'd settled there for this reason previously provided a situation that attracted more. After the beginning of open acceptance of this sort of difference during the 60's, many more were attracted and moved there. (http://www.greenspun.com/bboard/q-and-a-fetch-msg.tcl?msg_id=007Cix)
Posted by Dr. Dennis McClain-Furmanski PhD  on  Sat Apr 21, 2007  at  09:47 AM
I do also remember the exhibit in the Toronto museum, as I lived across the lake in Rottenchester, N.Y., and remember how " authentic" the experiment display looked. Now with the wisdom of revisionist skepticism, I see that things aren't always as they appear, realizing that the display was an authentic hoax. Were the researchers intending to produce an effect that would have the museum visitors come away with a preconceived conclusion about overpopulation and utopian environments? Or did they just have a limited budget to represent authentic behaviors? Anyway, the flick " Rattitoulle " is real...the tooth fairy told me.
Posted by Henry Michaloski  on  Wed Jan 16, 2008  at  06:24 AM
I grew up observing this experiment dozens of times over many years at the Ontario Science Centre. It was run completely, to the death of the last gerbil, twice in the 1970s and was taken down in the 1980s as far as I remember. The subjects were gerbils not mice. I had my own gerbils at home so it was important to me what they were. In 1995, abouts, I was looking for a paper to back up what I saw and so I went to ask the scientists at the centre for some follow up information. No one remembered it. If it was a hoax, which I doubt, I haven't seen any evidence that it was, including in these posts. The centre has a good reputation. I follow the news closely and there has never been a scandal at the centre. The gerbils were given a consistent floor space of about 8 metres, three levels of housing and an unlimited amount of food. Over three years the population grew to about two hundred or maybe less - I couldn't see them all at once. Eventually they all died. That is what I saw.
Posted by Geoffrey Hamilton  on  Wed Jun 04, 2008  at  09:08 AM
Posted by Nori Maki  on  Mon Jul 07, 2008  at  07:59 AM
Here's a link to the mice study.

Posted by Mark Nowotarski  on  Fri Nov 07, 2008  at  08:32 PM
I remember seeing a piece on this study on 60 minutes many, many years ago. I took population studies in college and tried to simulate it. I forget all the details of the study, but as I recall aggression, catatonic states (obstensively simulating drug consumption), infertility,homosexually, and in the last stages canabalism all increased exponetially even while the food source remained stable. Not exactly substatiating Malthus but perhaps a correlate to his theory.
Unfortunately for me and my grade, my experiment partner kept the animals over Christmas break, delegated the task of feeding them, which didn't happen, and all but one were dead or killed on his return. I was spared the scene.
Posted by Coco  on  Wed Dec 23, 2009  at  09:56 AM
I taught highschool senior biology in Ontario. When teaching ecology I also covered population ecology. For that reason I showed a film. Desigh With Nature by Ian McHarg. The film started with the crowding experiment. The commentary described the changes in the rats; increased aggressiveness, loss of maternal instinct, increased homosexuality and withdrawal from reality. While the talk continued the film switched to the strees of New York and the words fit exactly.
Posted by fred theaker  on  Sat Jan 16, 2010  at  10:44 PM
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