They are driven toward the predators when food becomes scarce. Their numbers fluctuate, but stay within the carrying capacity of the vegetation. When there are too few lemmings, the foxes starve. The snowy owl also hunts the lemmings. Snowy owls will leave the area when lemmings become scarce, and many do not return, but are killed by predators outside the tundra.
Some areas even have migrating reindeer or caribou.
The population dynamics remain carefully balanced, however. The plant communities are fragile, and the availability of light, warmth, and nutrients places absolute limits on the growth possible. This material may be used freely for instructional purposes but not sold for a price beyond the cost of reproduction.