Sloths have the least muscle mass of any mammal.  They are also herbivores (two-fingered sloths are somewhat omnivorous) which is a diet that doesn't bring in a lot of calories.  Therefore they don’t have a lot of calories to exert or a lot of places to store energy.  By being slow they can save precious energy while searching for their next meal so they don’t get sick or starve to death.

mom and baby two-fingered sloth resting

Sloths are excellent climbers but they can also be a little clumsy.  They are not known for their vision (although three-fingered sloths have much better vision than two-fingered sloths) or their balance.  However, they are extremely flexible and have a strong grip.  By moving slowly through the trees, they are able to plan their travel route more carefully and lessen the chance that they will fall somewhere dangerous.  Sloths are actually great at falling, however if they fall on something hard or pointy (or man made structures) they are more likely to get harmed in the incident.

three-fingered sloth climbing

There aren’t many things more important for sloths than not getting eaten by a predator.  Obviously, that means the end of everything for them.  By being slow, sloths are able to be silent.  We have watched sloths for thousands of hours in the forest and can attest to their ability to stay hidden.  Not only through amazing camouflage skills, but also through their ability to move silently through the forest canopy.  If a predator can't hear them, then they are more likely to not find them.

two-fingered sloth hiding