Cute, but misinformation.
Pictured is a river otter. Unlike sea otters, river otters do not have skin "pockets" (although they may carry around rocks to use as tools).
(Obligatory "I am not a biologist," however a quick Internet search seems to confirm this.)
"Without me, it is nothing. Without it, I'll just pick up another rock."
I think it's worth mentioning that they keep the stones with them to use them as tools.
They eat mollusks, crustaceans, and use their stone(s) to break their hard shells. They place the prey on their chest and beat it with a stone, which they hold between their paws, until they break it.
This is the best pocket pic i could find. The otter is stretching, revealing 2 stones in the pocket.
So it's an armpit? Or is it a marsupial thing?
The otter in the OP is a river otter (probably american river otter)—I'm like 90% sure they do not have pockets. The otter in the comment is a sea otter (in case the watermark didn't give that away)—they have skin folds that's often described as pockets near-ish to the armpit.
Neither of them are marsupials—they both belong to the family Mustelidae (which also include badgers, weasels, etc).
Suddenly understanding how they can smash shellfish on
the chesttheir chests.
