SLOTH (from AS. slaw, OHG. st0o, dialectic Ger. sehlPw, sehlo, Eng. slow). An edentate mammal of the family Bradypodiffir. re markably adapted to an arboreal life, and repre sented by many species, all residents of tropical America. They vary in size from that of a small bear to that of a cat. They feed on the leaves, buds, and young shoots of trees, among the branches of which they are born and spend their entire lives, rarely and unwillingly de scolding to the ground. They do not walk upon the branches, hut cling beneath them, with the back downward, and they can progress, if they please, with the agility of monkeys. They are chiefly nocturnal, resting sleepily during the day, from which circumstances, and from a misun derstanding of their habits generally, the mis nomer of 'sloth' arose.
The fore legs are much longer than the hind ones, and the feet are furnished with very long sharp claws, curved into hooks by which sloths hang beneath the branches even in sleep. A pe culiarity of the group is the extraordinary num ber of dorsal vertebra-. The head is round, and the muzzle so short that the face is monkey-like. Although members of the order Edentata, sloths are by no means 'toothless.' There are no in cisor teeth, but sharp canine teeth, and eight molars in the upper, six in the lower jaw. The molars are cylindrical. and are adapted merely for crushing, not for grinding, the food. For this, however, there is compensation in the stomach, which is somewhat imperfectly divided, by trans verse ligatures, into four compartments, for the longer retention and more thorough digestion of the food. The hair is coarse and shaggy. affords an excellent protection from insects, mid gives sloths such a gray appearance that they are not readily observed except when in motion. This protective effect is enhanced by the growth upon it of a minute grayish-green alga, allying the hair almost precisely in color with the 'gray beard moss' that drapes tropical trees, and amid which they are fond of hiding.
The sloth produces only one young one at a birth. which clings to its mother till it becomes able to provide for itself. The voice of the ani mal is a low plaintive cry. Less than a dozen species of sloth are known, grouped in two subfamilies, according to the number of toes on the fore feet. All have three toes on the hind but the Cholopodirre have only two toes on the front feet, the Bradypodinze three. The latter have nine cervical vertebrae and twenty abdominal, and of the latter 15-17 bear ribs; while the former have only six or seven cervical vertebrae, and twen ty-seven abdominal, of which 23-24 bear ribs. Of the Cholapodime, or 'unaus,' there are only two species, the two-toed (Chokrpus didaetylus), which is common in Brazil, and a Central Ameri can species (Cho/opus Hoffmanni), which is lighter colored. They are about two feet long. Of the Bradypodime conspicuous species are the three-toed sloth ( Bradypus tridaelylus) and the collared sloth (Bradypus infuseatus). The lat ter is the largest of the family and has a collar of long black hair around the neck, behind which is a patch of pale orange. Consult: Beddard, (London and New York, 1902), and the memoirs there cited relating to anatomy a ml classification; also Lydekker. Royal Natural His tory, vol. iii. (London. 1 895) Alston, mals," in Biologia Centrali-Amerieana (London. 1579-82) ; and Bates, Naturalist on the Amazons (2c1 ed., London, 1592). For fossil forms of the sloth, see GlAxonoNTA; MEGATIIERIUM ; YLODON ; .A1AMMALIA, FOSSIL.