The Life of the Sloth: Final Draft

This discussion topic submitted by Gail Corrado ( at 9:45 PM on 6/29/99. Additions were last made on Friday, December 20, 2002.

A beautiful Sloth in a Cecropiatree in NW Costa Rica near Arenal Volcano

I. General facts and background about the Sloth
A. SLoths are of the order Xenartha (Edentata)
"Edentata" means toothless, but sloths are not toothless.
B. Same order as anteaters and armadillos
1. characterized by simple peglike teeth
C. They are relatives of the extinct giant ground sloths
D. five species of sloths, all in neotropics
1. two species in Costa Rica
Bradypus variegatus or the three-toed sloth
Choloepus hoffmanni or the two-toed sloth
2. these common names are misnomers because all sloths have three fused toes; it is the number of claws that the two and three-toed name comes from
II. Elegant adaptations
The sloth is so named for its very slow movements. Many of its characteristics are adaptive for both life in the canopy and a slow life.
They are strict vegetarians, and their slow movement is an adaptation that allows them to conserve the little energy they receive from their vegetarian diet.
A. Long curved claws allow sloth to hang upside hang and cling from trees without using much muscular energy
B. Have approximately half the amount of muscle mass of any other similar sized mammal (maintaining muscle takes energy)
C. Fur grows from belly to back to allow rain to drip off
D. Hair is grooved, and algae grows in these grooves during the wet season. THis gives them a green color (camouflage). As many as 900 species of beetles, mites, ticks and sloth moths have been found to live and feed on this algae.
E. They have nine vertebra, where most mammals have seven. THis allows them to turn their heads 270 degrees. They can actually turn their heads right side up while hanging upside down.
F. Lower body temperature nearly 10 degrees Farenheit at night and rise to treetops to sun themselves in the morning and raise the body temp.
G. Each individual sloth has a specific menu of trees that it eats. THese specific trees are determined by microorganisms that live in the sloth's gut. These microorganisms are passed on to infant sloths when the mother shares her food. This specific diet has led to decreased competition among sloths in an area. because this specific diet was only discovered twenty years ago, many sloths died in zoos because they were not getting the correct diet.
III. Lifestyle
A. 1.6 ha homerange
B. .5 km average speed
C. Abundant in the forest, although not very visible. One study counted approx. 700 sloths/km sq. versus 70 howler monkeys/km sq. (Sunquist and Montgomery, 1973).
1. make up approx. 70% of arboreal mammalian biomass (Sunquist and Montgomery, 1973)
D. Can't walk but swim well; they do the breaststroke
E. Mate upside down, and parental care is done by the female. She gives birth approx. 263 days after conception. The infant is carried on its mother's belly for six months. After six months, the mother leaves the baby in her home range to fend for itself.
F. The sloth descends to the ground once a week to defecate. It climbs down the trunk of a tree, digs a hole, defecates in it, and covers it up before climbing back into the tree. Many of its sloth moth friends hop off at this time to lay their eggs in the feces. This whole process takes nearly an hour, and it is unclear why the sloth does this. It puts the animal in a very vulnerable position. It has been suggested that the sloth is preferentially fertilizing its favorite trees, but this hypothesis has never been tested.
G. When captured or chased, the sloth will not usually fight back. It will sit motionless and cling tenaciously to its tree, or it will climb very high into the canopy where larger predators (such as jaguars) cannot reach it.
H. Most often seen in cecropia trees. For many years it was thought that this was the sloth's favorite tree. The recent knowledge of the specified diet has refuted this suggestion. We now know that it is not that the sloth particularly likes the cecropia tree, but it is very easily seen in these trees.
I. Lifespan can last as many as forty years.
IV. Some differences between the three-toed and two-toed sloth
A. Two-toed is more aggressive and eats fruits and flowers as well as leaves, and it is larger than the three-toed (8-9 kg versus 3-5 kg).

Emmons, Louise H. Neotropical Rainforest Mammals: a field guide. The University of Chicago Press, 1990.

Hoke, John. Discovering the World of the Three-toed Sloth. Franklin Watts, 1976.

Reid, Fiona A. A Field Guide to the Mammals of Central AMerica and Southeast Mexico. Oxford University Press, 1997

Sunquist, M.E. and Montgomery, G.G. "Activity Patterns and Rates of Movement of Two-toed and Three-toed SLoths (Choloepus hoffmanni and Bradypus variegatus). Journal of Mammalogy, 54:946-954.

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