<P> Three - toed sloths are about the size of a small dog or a large cat, with the head and body having a combined length around 45 cm (18 in) and a weight of 3.5--4.5 kg (8--10 lb). Unlike the two - toed sloths, they also have short tails of 6--7 cm (2--3 in), and they have three clawed toes on each limb . They are frequently referred to as three - toed sloths, but all sloths have three toes; the difference is found in the number of fingers, meaning that they are now more appropriately referred to as three - fingered sloths . This idea was first implemented by Judy Avey - Arroyo, cofounder of the world's only sloth sanctuary, but is now recognized in numerous publications as the correct terminology for these animals . </P> <P> Unlike the two - toed sloth, three - toed sloths are agile swimmers . They are still slow in trees . The offspring cling to their mother's bellies for around nine months . They cannot walk on all four limbs, so they must use their front arms and claws to drag themselves across the rainforest floor . </P> <P> Three - toed sloths are arboreal (tree - dwelling), with a body adapted to hang by their limbs . They live high in the canopy, but descend once a week to defecate on the forest floor . Their long, coarse fur often appears greenish, not due to pigment, but to algae growing on it . Sloths' greenish color and their sluggish habits provide an effective camouflage; hanging quietly, sloths resemble a bundle of leaves . Large, curved claws help sloths to keep a strong grip on tree branches . </P> <P> They move between different trees up to four times a day, although they prefer to keep to a particular type of tree, which varies between individuals, perhaps as a means of allowing multiple sloths to occupy overlapping home ranges without competing with each other . </P>

When algae lives on a sloth it is considered