Minecraft wiki entry for Development_versions, associated text: Adults and cubs spawn randomly as passive mobs in ice plains, ice mountains, and ice plains spikes.
When hit, the adults will attack the player, the cubs will run away (very fast, similar to baby zombies).
Additionally, adults will always attack the player when their cubs are around.
Can swim faster in water than the player.
Cubs will follow their parents.
Drops 0–2 raw fish (75% chance) or 0–2 salmon (25% chance), each increased by 1 per level of Looting.