Sloths have a thick brown fur coat with specialized functions. For example, the fur grows in the opposite orientation relative to all other mammals, presumably to provide protection against the elements. Some have fur with a greenish color due to the presence of colonies of green algae. Sloths reach a size of approximately 61 cm long and have a short flat head, big eyes and long curved claws on each foot for clinging to tree branches. They are nocturnal mammals; that is, active at night and sleeping all day. Males are solitary, while females have been seen in groups. The most notable characteristics are a low metabolic rate and a body temperature of 91F. Their diet consists primarily of tree leaves and this food source can, in some instances, contribute as much as two thirds of the animal's body weight. The digestive process to break down these plant foodstuffs can take as long as one month. The sloth also can absorb nutrients from the colonies of green algae inhabiting its coat by licking its fur.
The sloth inhabits the tropical rainforests of South and Central America. The animal spends a majority of its life in the trees hanging upside-down, where slow movement and excellent camouflage protect it from predators. Since sloths are herbivores (plant-eaters) this arboreal environment is ideal for survival. Only one species of sloth, Bradypus torquatus, is considered endangered at present, but the continued deforestation of South and Central America could cause other species to be similarly classified in the near future.
The two-toed sloth, Choloepus hoffmanni, will be sequenced as part of an NHGRI initiative to expand sequencing of mammalian genomes. The DNA for this sequencing effort was provided by courtesy of Dr. Oliver Ryder, at the San Diego Zoo's CRES. The C. hoffmanni genome will be sequenced to 2X whole genome coverage with plasmids plus a low coverage of fosmid end sequences (around 0.1X). For more information on the mammalian genomes represented in this initiative please visit the Genome Sequencing Proposal page. Funding for the sequence characterization of the sloth genome is being provided by the National Human Genome Research Institute (NHGRI), National Institutes of Health (NIH).