Hi i need urgent help on a report i am doing can someone please help me?

[Guest Pie]

Hi i have been on loads of websites but i cant find what i'm looking for. i am doing a report on lemmings and their population explosions for school but i cant find out what the causes of the increase in their population is, please help me!?

[-Demosthenes-]

http://www.abc.net.au/science/k2/moments/s1081903.htm

Heres the part:

Many of the rodents have strange population explosions. One such event in the Central Valley of California in 1926-27 had mouse populations reaching around 200,000 per hectare (about 20 mice per square metre). In France between 1790 and 1935, there were at least 20 mouse plagues. But lemmings have the most regular fluctuations - these population explosions happen every three or four years. The numbers rocket up, and then drop almost to extinction. Even after three-quarters of a century of intensive research, we don't fully understand why their populations fluctuate so much. Various factors (change in food availability, climate, density of predators, stress of overcrowding, infectious diseases, snow conditions, sunspots, etc) have all been put forward, but none completely explain what is going on.

 

http://www.snakebreeder.co.uk/html/lemming.html

 

Here the part form here:

What seems to happen is that as the lemming numbers go up so does the stoat population. Each stoat can kill lots of lemmings. One day the stoats are eating lemmings faster than the lemmings can reproduce. Lemming numbers plummet. Then there is no food for the stoats ( who specialise in eating only lemmings). The result is lots of stoats die because they can not get enough food. In fact the stoat numbers drop to very low levels. This gives the lemmings time to increase in number again. As the population of lemmings expands there is more than enough food for those stoats, and the whole thing starts again.

 

I hoped I helped, and for future reference Google Google Google.