The Brainliest Answer!
It is because of their small size. heat loss is directly propotional to the surface area, small animals hav large suface area relative to their volume, they tend to lose body heat very fast. so they can't survive in extreme cold region.
1 5 1

This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
Very small animals have large surface area with respect to volume, so there is more chance of heat loss, hence, they are rarely found in polar regions..
1 5 1