Why are sloths so slow?
For grown-ups: the science
Sloths move slowly to save energy from their leafy meals, and their bodies are made for careful tree climbing.
Most sloths have a low-energy diet dominated by leaves, which are difficult to digest and provide relatively little usable energy. They have slow metabolisms and anatomical adaptations for suspensory tree life, including long limbs and curved claws. Algae commonly grow in grooves of some sloths' hair and may contribute to camouflage, though its importance varies by species.
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Transcript
High in a leafy tree, a sloth hangs upside down. Why does it move so slowly?
Sloths eat mostly leaves, which do not give them much energy. Moving slowly helps them save that energy.
Their bodies are built for hanging, with strong arms and curved claws. In trees, slow climbing keeps them steady.
Green algae can grow in a sloth's fur. Its greenish fur can help it blend in with leafy branches.
So sloths are slow because leaves give little energy, and life in the trees fits their careful bodies.