BRITISH GUIANA (1) Lit 
heard of a sloth attempting to swim and feel that it almost cer- 
tainly fell in the water in some way. 
This species of sloth is smaller than the other species in British 
Guiana—the Two-toed—and is more specialized in its diet, living 
mainly on the leaves of the cecropia, or Umbrella Tree. 
The sloth is a good example of the way the tree-dwelling mam- 
mals of South America have adapted themselves to a particular 
mode of life. Several species of monkeys, two species of ant-eaters, 
the tree-porcupines and the opossums, all have prehensile tails 
with which they can grip branches and use as a fifth limb. The 
sloth, on the other hand, has dispensed with his tail (all that 
remains is a rudimentary stump) and travels along branches 
upside down. His long legs, terminating in long hook-like claws, 
are specially adapted for this purpose, and are so constructed that 
it is impossible for him to walk in an upright position. This is no 
handicap, for his life is spent in the tree-tops, where he moves 
with ease from one to another seeking sustenance. 
Although adapted for a purely arboreal existence there are times 
when the sloth finds himself compelled to progress along the 
ground. This he can do with difficulty, at a tortoise-like speed. 
In this situation his action is rather like that of a man lying on 
the ground, face downwards, going through the actions of the 
over-arm stroke in swimming. One forearm is stretched forward, 
then by leaning on that and pushing with his feet he drags the 
body along while the other forearm comes forward. Although the 
sloth can progress along branches only in an upside-down posi- 
tion, and usually feeds in this position, he normally sleeps upright 
clinging to a branch, his body doubled up so that his head rests 
between the forearms on his chest. 
Among the special features of the sloth are his ability to go long 
periods without food; his hard and tough body, capable of sus- 
taining injury with little or no apparent discomfort; ability to 
turn the hind feet through a wide angle to facilitate the grasping 
of branches; ability to turn the head round through 180°; the 
retarded passage of food through the intestinal tract (in experi- 
ments it has been found that foods, colored for identification, have 
taken up to seven weeks to pass right through the animal); and 
the retarded defecation (on average once a week). In the Three- 
