The Astonishing Feat of Sloth Swimming

Sloths are naturally good swimmers. On land they travel approximately 3 meters per minute, however, whenever they are swimming they travel up to 13.5 meters per minute [1]. How is it that sloths are so slow travelling across land but are able to swim 4 times faster while in the water? You could say it is love… Sloths use their amazing swimming abilities to swim from island to island when in search for a mate... [2] Or maybe it is their long arms that provide more leverage to displace more water on their speedy voyage. Here we will discuss more of what makes sloths such unique swimmers. 



Sloth SwimmingFirstly, let’s look at exactly how sloths transport themselves. It is easy to see how they move in the trees, swinging from limb to limb using their arms, legs and hook like claws. It is actually very rare for a sloth to leave the trees and make a trip on solid ground. However, in rare cases when it does, it must crawl. Although sloths can stand up on their own, their muscles are not strong enough to keep them in an upright position while walking. For this reason, on the ground, sloths must use their arms to pull themselves wherever they go [3]. If you consider that sloths do not have the strength to walk, it would also make sense that it would be difficult to essentially drag/crawl yourself across the ground using your arms. Who here has done a similar exercise in gym class such as the army crawl? It’s not easy and it is probably even harder for sloths! 



Now using this same methodology for swimming, sloths use their arms to pull and displace the water behind them to propel themselves forward. However, the difference here is that they do not havSloth Swimminge the friction and weight of having to drag themselves and pick themselves up across the ground. Additionally, if you watch a sloth swim, it is able to move its arms in a continuous motion possibly providing more force in a shorter amount of time to move itself forward. If you watch a sloth crawl on land, it has to move its arms in more of a “back and forth” motion versus a more circular motion. Another important piece of information is that sloths have a very gassy stomach, similar to that of a cow. It basically acts as a buoy for them to float along the top of the water [4]. This combination of lack of friction, flotation, continuous motion, and lengthy arms could very well be the reason why sloths are such better swimmers than they are moving across the ground. 





Of course much of this is speculation, you decide for yourself! With this surprising feat of sloth swimming, hopefully you’ll appreciate just one of the many interesting things we can learn about sloths. 

  1. Goffart, M. (1971). "Function and Form in the sloth". International Series of Monographs in Pure and Applied Biology. 34: 94–95.
  2. BBC (4 November 2016), Swimming sloth - Planet Earth II: Islands Preview - BBC One, retrieved 17 April 2017
  3. Three-toed sloth. Encyclopedia of Animals. August 2017:1. Accessed July 27, 2019.
  4. Cooke, L (2018) The Truth About Animals. New York, NY: Hachette Book Group

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