Sloths
South American sloth photo courtesy of CalPhoto.
DB: This is Earth and Sky. A listener writes, “If sloths are so slow, how come they haven’t been gobbled up by predators and gone extinct?”
JB: On the contrary, the slow movements of a sloth are the essence of its success. Sloths are tree dwelling mammals with tiny heads and long arms. They live in the tropics of South America. If you could see one, you might be amazed by the deliberate way a sloth moves its limbs, almost as if it’s moving in slow motion.
DB: The sloths’ predators include large birds of prey – such as the harpy eagle. These hunters usually detect their prey when it moves against its background. Sloths keep their motion to a minimum – and they move very slowly when they do shift position. So they’re less visible to predators. What’s more, sloths have a unique form of camouflage. Most mammals have relatively smooth hair, but the hair of a sloth is pitted or grooved. Green algae live in the grooves -which helps the sloth blend in with its leafy environment.
JB: It’s good that sloths tend to stay high up in the trees – safe from fierce hunters like jaguars and ocelots. Slowness would make them vulnerable on the ground – which is perhaps why the ground sloths that used to roam North America are now extinct. To ask us your science question, come to earthsky.org. And thanks today to the National Oceanic and Atmospheric Administration and to the National Fish and Wildlife Foundation. We’re Block and Byrd for Earth and Sky.
Additional Teacher Resources
San Francisco State University, Department of Geography: Brown-Throated Three-Toed Sloth
This site provides an extensive natural history of the brown-throated three-toed sloth. The report is presented using scientific language geared more toward secondary students. Included in the report is a description of the species, habitat, natural history, evolution, distribution, and current status.
EnchantedLearning.com: All About Sloths
The sloth is a slow moving mammal that lives in trees. Sloths spend most of their lives hanging upside-down from tree branches; they eat, sleep, mate, and give birth upside-down in the trees. This site provides “fun facts” and information geared more toward younger students. It also contains photo images and links to more information on several species of sloth.
The National Geographic Society: Sights & Sounds: Brazil’s Atlantic Forest
This site provides an excellent interactive resource for understanding the ecosystem in which the tree sloth lives. The site consists of a multi-media Flash presentation that explores the fascinating ecosystem of Brazil’s eastern rainforest with a heavy emphasis on the tree sloth population.
