Expert: Jonathan Wright - 3/26/2007

Question
Hello Mr. Wright, I am doing a report for my high school English report. The report is about the common misconception about lemmings having suicidal tendencies. I was hoping you could answer a few questions on lemmings for me. Thanks in advance!

How do Lemmings go about organizing themselves into a migratory herd when food is scarce?

Can you briefly tell me what causes the cyclic influx in the lemming population?

In your opinion, what is the root of the widespread belief that lemmings are suicidal in nature and hurl themselves on cliffs? If you believe Disney’s film “White Wilderness” is the root, do you believe there are any other causes?

Do you have any other interesting facts about lemmings?


Answer
Dear Ryan

I was watching a television programme called "Qi" a few weeks ago and the presenter said that the story about suicidal lemmings was first mentioned by Arthur Mee in his children's encyclopaedia, dated 1906. This predates "White Wilderness" by several years.

All the best

Jonathan
Dear Ryan

Thanks for your questions. I also wish to thank the authors of the websites and books I used.

1. When I studied lemmings as part of my degree, it seemed that a population of lemmings split into two groups when the population rose too high for all the animals to survive on the food available. Some of the lemmings stayed behind and could thrive on the food available. The rest migrated to find alternative food sources in less densely populated areas. Many died by falling off cliffs, drowning, exhaustion or from being eaten by predators. The lecturer said that this was not an example of mass suicide. If all the lemmings stayed, the group would probably starve to death. If the migrants died out, they still had relatives that stayed behind.

Volume 41 of “Animal World” deals with voles and lemmings. It suggests that the lemmings become more aggressive as the population rises. The older, settled animals tend to push the younger ones out, so the migrants tend to be younger individuals.

http://www.xeye.org/1995-2000/LemmZoo.html#l_lemmus says that each lemming uses sight to choose its own direction and normally follows it alone and as close as possible. Groups of lemmings walk on the same path only when they reach obstacles.

http://ladywildlife.com/animal/norwegianlemming.html says that the lemmings do not travel to a specific destination and may follow paths and roads that lead them through areas of human habitation. Volume 41 of “Animal World” suggests that the hordes get larger as their paths converge. Their jostling often brings on a blind panic that drives on the lemmings. This attracts more predators, which helps to reduce numbers. Therefore it seems that lemmings do not organise themselves into a migratory herd when food is scarce.

2. http://www.xeye.org/1995-2000/LemmZoo.html#l_lemmus and other sources state that scientists are unsure why lemmings undergo cyclic changes in population about every 3-5 years. There may be cyclic variations in fertility. Usually there are 2 litters of 5 young each year, but this can rise to 4 litters of 2-8 young.

http://ladywildlife.com/animal/norwegianlemming.html says that females can reach sexual maturity at 14 days. When food is scarce, or when lemmings are forced to migrate to new feeding areas, their reproductive capacity automatically slows down.

Walter Sullivan (http://query.nytimes.com/gst/fullpage.html?sec=health&res=9B01E5D81539F937A35753...) wrote that a substance that appears in grass each spring may act like a super hormone, abruptly turning on reproductive activity in some mammals when they nibble the appropriate plants. It may account for population explosions of lemmings, as it increases litter size and seems to accelerate maturation. This helps the lemmings survive in hash, unpredictable environments, where they may have only one season in which to reproduce. Hormones are also mentioned in http://links.jstor.org/sici?sici=0022-2372(196205)43%3A2%3C171%3ATIOTNL%3E2.0.CO%3B2-L, but you need to be a subscriber to access it.

3.I think you are probably right that the film "White Wilderness" popularised the belief that lemmings are suicidal, although http://ladywildlife.com/animal/norwegianlemming.html says that people believed that lemmings were suicidal back in 1532. http://www.snopes.com/disney/films/lemmings.htm is a useful site for you. It states that the film crew for "White Wilderness" induced lemmings into jumping off a cliff and into the sea in order to document their supposedly suicidal behaviour. The site says that lemmings are more likely to kill each other than to kill themselves when the population is high.

There are many other interesting facts about lemmings. For example, the collared lemming has a white coat in winter and grows enlarged claws on its feet to dig through the Arctic snow (see http://library.thinkquest.org/3500/lemming.htm for more details).

I hope this has answered your questions.

All the best

Jonathan