Otters likes shalow lakes and watterfalls. Best way to tame otter is to kill all salmons around it, cause corpses has long time before it disappears and straight away feed them without any intervals cause they dont have cooldown on feeding time. After tame pick it up and you will get insulation from cold. Leveling otter is best to give all stats to oxygen as it increase insulation resistance. And you will forget biome struggle :) good luck finding them.

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