Hello. This was fun to write, but it was really hard to keep it under 250 words. If you really want it under 250, I suggest deleting the last sentence of the 3rd paragraph, about caribou and semi-hibernation. :)
I hope this works well for you.
The tundra is a vast plain in frozen regions such as Siberia, northern Canada, and northern Alaska. In the tundra, permafrost exists year round just beneath the surface, and the growing season is extremely short. Only a select few animals are equipped to survive life in this frozen wasteland.
Among the smaller residents of the tundra is the arctic fox. The arctic fox, around the size of a common house cat, lives in burrows. These fox are scavengers, often following larger predators, such as the polar bear, and eating their leftovers. Another small mammal is the ermine, weighing less than 15 ounces. They have very sharp teeth, perfect for eating anything from small insects and rodents, to birds. During the long winter season on the tundra, the ermine can actually dig underneath the snow, in search of rodents hiding within.
Caribou also live on the tundra. Often called reindeer, caribous are among the largest of the deer family, with both males and females growing antlers. During snow cover, caribou will scrape away the snow with their feet and antlers, eating lichens, and snow covered vegetation. During times of extremely harsh conditions, caribou can go into a state of semi-hibernation.
Also in the tundra is the snowy owl, whose keen eyesight lets it see even the smallest prey scavenging on the tundra floor. Then there is the foraging grizzly bear, who can hibernate during extreme temperatures, and the polar bear, the largest land predator in the world, whose black skin and thick fur keep him incredibly warm, even on the tundra.
Hares, pikas, and rabbits
Ogilvie mountains collared lemming
Unalaska collared lemming
St. lawrence island collared lemming
Read more at the list of biomes of the world...