Mod Polar Bears PE description

The polar bears spawn in ice spikes and ice plains biomes. It’s only the bear cubs (or baby bears) which can be tamed and for that you need some bones.

Polar Bear Spawn Egg (2854)
If you try to get close to a cub when there’s an adult nearby there’s a good chance it will try to kill you. The polar bear adults are only neutral (or non-hostile) whenever they don’t have any cubs in their surroundings. (This is only true if you are playing in survival mode. If you are in creative mode, you will be safe.)