Sloths are so named because of their very low metabolism and deliberate movements. "Sloth", related to "slow", literally means "laziness," and their common names in several other languages (e.g. French "paresseux") also mean "lazy" or similar. Their slowness permits their low-energy diet of leaves and avoids detection by predatory hawks and cats that hunt by sight. Sloths are almost helpless on the ground, but are able to swim. The shaggy coat has grooved hair that is host to symbiotic green algae which camouflages the animal in the trees and provides it nutrients. The algae also nourishes sloth moths, some species of which exist solely on sloths.