To Poop and/or Die. To Poop...for the Team
Figure 1. The babes, two two-toed sloths
Around the world, many human cultures consider the concept of sloth, slothiness or the voluntary refusal to act or move and do the things a society expects one to do as sinful and at the root of all evil and darkness. Further, many believe laziness is a blight to humanity and a hindrance to the pursuit of happiness.
To the contrary, the scraggly coated, gentle and ever -smiling mammals with the unfortunate namesake known as los perezosos or the lazies in Spanish are anything but slothful. Instead, they are masters of symbiosis and energy conservation with shocking behaviors that make them seem like the ultimate dare devils, both gutsy and foolhardy in the mating game.
Figure 2. INTREPID. A Three-toed sloth
Among the main types of sloths are the Two-toed Sloth and Three-Toed sloth that both reside in the neo-tropical forests of South and Central America.
FIgure 3
While once rich with over 50 different species that evolved 50 million years ago, the vast majority went extinct from a combination of climate change and atalatyl-happy humans.
Figure 4. Delicious ground sloth totally unbeknownst to the menace beneath.
Unlike their extinct mega- relative, the mammoth-sized Ground Sloth that weighed 4 tonnes, most sloths today are about 20-30 inches in length and weigh roughly 9 pounds. They sport furry coats, small snouts, an indefatigable smile, and 4 inch long claws on their fore and hind feet to cling and hang nearly 90% of the time from tree limbs. Fantastically well-designed for tree-life with special joints, they not only eat whilst in the trees but also mate, give birth and sleep in the trees. The bulk of their diet consists of leaves from the Cecropia tree, which the Three-toed sloth relies almost entirely on for food, while the two-toed sloth has a broader dietary menu including small reptiles, birds, fruit and insects. Life on leaves, however, is an incredibly nutrient starved one so the sloths have had to develop some unique adaptations to weather extreme energy constraints.
Figure 5. The Brown-Throated Sloth.
Like cows, they have 4-chambered stomachs loaded with bacteria to help break down the tough fibrousy leaves, but since their food is so poor in quality anyway, the digestion process for a single leaf can take up to 30 days! As a result, they have the slowest metabolic rate of all mammals, eat sparingly, and hence they move as minimally as possible as an INGENIOUS energy saving mechanism.
Figure 6. Belly : Body Mass Ratio = 33%
If not for a smart physiology, even breathing for a perpetually inverted lifestyle would be a nearly impossible feat since it would drain a lot a sloth’s precious energy and their lungs may catastrophically collapse under all their other organs. To overcome this challenge, their viscera are tethered to their ribs and hips with a stretchy fibrous-y tendon-like strap. This physiological feature saves them 7-13% of energy, which is no small potatoes for them.
Figure 7. Organ Tethers. Credit: Ed Yong-National Geographic
Approximately one-third of their total body weight is made up of the contents of their stomach, a hefty load they must carry all day long until they can finally relieve themselves; however unlike other mammals of comparable size that blissfully poop out on average once a day, sloths store and build up their waste for an entire week! While Two-toed sloths just drop their poop like a bomb, Three-toed sloths engage in a baffling behavior that on the surface seems incredibly self-defeating.
On a weekly basis, Three-toed sloths slowly descend from the canopy to the tree base for a ritual pooping and they do so in the same spot, without fail. Worrisome for the sloth, though, when at ground level, they are extremely vulnerable to a whole slew of treacherous predators including sharply taloned harpy eagles and shimmery toothed jaguars. Nearly 50% of all sloth adult mortality cases are related to predators devouring them during their risky pooping exercise. Behold the pooping:
Figure 8.
For a more direct pooping video, click here..if you’re into that sort of thing.
This practice is not only deadly, but the very act of climbing down to the ground at a rate of 15 feet per minute and returning to their perch for a total 6-hour operation is incredibly energy intensive, using 8% of their limited energy budget. Behold the crawl:
Figure 9.
Why not poop-bomb from the security of the tree like their two-toed cousins? What behooves them to be so brazen and reckless? with their lives.?
Researchers have speculated it may have to do with what’s in their fur, which is teaming with life. Up to 3% of a sloth’s mass is neither stomach content nor of the sloth itself, but rather the 20-38 different taxa of microorganisms hitching a ride on their pelage. Sloth are host to an impressively diverse food web with the majority of organisms made up of microbes, while another 33% is green algae, and the remaining lot of various insects including instrusions (literally, the collective noun for beetles) of cockroaches, and rabbles of ticks and moths. An individual sloth may have 100-120 moths shacking up.
Figure 10. Flurries of moth hairpins
A number of these critters are endemic or only found to live on the sloth and nowhere else. Within the last decade, scientists have found a fascinating three-part mutualism between the sloth and two of these endemic critters, including the green algae and a moth species commonly called, no less, SLOTHMOTH. Together, this triad relationship may confer striking benefits that outweigh the risks of the perilous descent to the loo.
Figure 11. Yes. Credit: Perrin Ireland
Every time the sloth comes down to defecate, female moths nesting in their fur take the opportunity to lay their eggs in their poop. Once the coprophagous larvae hatch, they eat the poop to energize their metamorphosis into an adult. After a couple revisits to the latrine, the newly matured moths emerge from the poop and nestle their way into the sloth’s coat where they’ll find their mates and ultimate die. The dead moth corpses then decompose with the help of a menagerie of detritivorous fungi that release ammonia NH4+ and nitrates NO3-, all of which serve as fertilizer for the green algae to spread their green colored glory across the sloth’s coat.
Figure 12. The Three-point mutualisms
A benefit of a green algal coat may be the optical magic of camouflage, and so a sloth can conveniently disappear among the trees to avoid predators.
Figure 13. Daring and donning das algal coat
The more moth insects that exist in their fur, the greater the concentration of nitrogen compounds there are and the more prolific the algal coat.
Studies have found that sloths also eat the algae, which not only are easy to digest, but carry five times as much lipid or fat, and their carbohydrates are much simpler to break down than from leaves. Although it is not well understood how the sloths are accessing the green algae, whether by licking them off their talons after they autogroom or somehow licking their fur directly, eating algae may have given them the key to ‘overcoming’ the poverty of their leaf-y diet”. According to sloth ecologist Jonathan N. Pauli, the moth insects may very well serve as “a portal for nutrients” that links their fur ecosystem with the outside environment. As a result, they may help them succeed as low-power-mode arboreal herbivores, granting them access to a much richer food reserve as sloths serve the moth life cycle to in turn, farm the algae. This farming/gardening behavior is rather similar to our previous story of leaf-cutter ants.
Figure 14. Ahoy... Just working on a 720 hour digestion
While there need to be more studies on whether the sloths can effectively survive without the algae or moths, other scientists scoff at the moth/sloth/algae farming hypothesis, saying the risky potty-break behavior is more in line with finding a mate. Females, when in heat, descend to the ground nearly every day for an entire week, defecating and leaving behind her special smell while she picks up smelly notes left by possible male suitors. The poop piles may be a personal dating ad exchange/trading posts. Whether it’s for slow-dating, or a more nutritious meal, scientists have yet to decipher. Is risking your life for a mate or a bite any more or less cray than texting or facebooking while driving? What about waiting 6 hours for a Cronut, or a Black Tap milkshake?
Figure 15 Black Tap Milkshake bomb.
Albeit, these sugar bombs aren’t necessarily going to energize your veritably exhausting life as a tree- hanging, poopy-moth-life-cycle facilitator.
Other fascinating studies yet to be further explored regard the sloth-coat-critters themselves, some of which have been found to have compelling defenses against strains of human cancers and bacterial pathogens. In sum, sloths have played complex badass roles in the neotropical forests. However, sloths face threats from logging and deforestation, and species like the Pygmy Sloth are critically endangered. In their defense, folks are seeking to educate the public and empower folks to restore and preserve their homes.
Figure 16. Melting hearts and prickly pride, one sloth picture at a time
Read the amazing story of a woman in Suriname who after having lost her dog, rescued 200 sloths that turned her house turned into a slothified convalescent home.
References:
Hrala, Josh. Watch: Why Sloths almost die every time they have to poop. Science Alert. http://www.sciencealert.com/this-is-the-horror-that-sloths-have-to-go-through-every-time-they-poop. June 24 2016. Accessed June 26, 2016
Nicholls, Henry. The Truth About Sloths. BBC-Earth. September 2014. http://www.bbc.com/earth/story/20140916-the-truth-about-sloths
Pauli, Jonatha et al. A Syndrome of Mutualism reinforces the Lifestyle of a Sloth. Royal Society Publishing. January 22, 2014. DOI 10.1098/respb. http://rspb.royalsocietypublishing.org/content/281/1778/20133006#ref-33
Suutari, Milla et al. Molecular evidence for a diverse green algal community growing in the hair of sloths and a specific association of Trichophilus welckeri. BMC Evolutionary Biology. 10:86. March 30, 2010.
Venema, Vibeke. The Woman who lost a dog and gained 200 sloths. BBC World Service. April 2014 . http://www.bbc.com/news/magazine-26734289. Accessed June 26, 2016
Wade, Nicholas. The Sloth’s Busy Inner Life. New York Times. Science. January 27, 2014. http://www.nytimes.com/2014/01/28/science/the-sloths-busy-inner-life.html?_r=0. Accessed June 26, 2016
Yong, Ed. To Breath Upside Down Sloths Tape Organs to Ribs. National Geogrpahic – Not Exactly Rocket Science. April 23, 2014. http://phenomena.nationalgeographic.com/2014/04/23/to-breathe-upside-down-sloths-tape-organs-to-their-ribs/. Accessed June 26, 2016












