Is the reason why sloths move so slowly because their neurons naturally have less myelin on the axon? So nerve signals like action potentials move really slowly along the axon and thus cause slower movements?


I think I heard about this in my biological psychology class but I can’t find anything when I try to search it online except for “low metabolic rates.” Is the reason in the title correct or am I misremembering?

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It doesn’t appear to be neurological. They are adapted to eat significantly less than most mammals. Less calories means less energy for muscle movement. The more you move the more energy you burn. If they moved fast and their metabolism was high then they’d need more calories. Their diet is mostly calorie deficient leaves, so their body has adapted to moving slowly to require less energy. Otherwise they would burn their calories and starve.

No that isn’t why sloths move slowly. Myelination of nerves would involve really fundamental genetic changes to sloths compared to other animals. Sloths move slowly because they aren’t trying to move fast, and even if they were they have very weak muscles and slow metabolisms that couldn’t support fast movement. The actual structure of their nervous system is similar to other mammals.

Actually down when we still had a military base in Panama I was visiting a friend. They were over by this bent tree poking at a moss covered sloth with a stick. Faster than you could blink your eyes, it swung its arms and claw at the stick and it dropped in 3 pieces. Then slow as molasses, it brought its arm back to the tree and rested its head. So they have the ability, just maybe not the desire to expend energy?