STANDARDS

CCSS: 6.RP.A.3.B, 6.RP.A.3.D, MP1, MP2, MP6

TEKS: 7.4B, 6.4H

Searching for Sloths

Meet a scientist who is studying the world’s slowest mammals

Suzi Eszterhas/Minden Pictures

Pygmy sloths living in Panama swim from tree to tree to find food.

Splash! A pygmy sloth drops out of a red mangrove tree, falling into the crystal-blue water. It starts swimming by leisurely paddling its long arms. Minutes later, the sloth reaches a nearby tree root. It slowly pulls itself up. Then the sloth begins its slow climb up to the top branches of the tree in search of its next meal.

All sloths can swim. But off the coast of Panama lives the only sloth known to swim in salt water—the pygmy sloth. Pygmy sloths are the most recently identified species of sloth. No one is sure how many there are, but there aren’t a lot. Because they are so rare, scientists didn’t determine they were a distinct species until 2001!  

math-090318-hangingwithslothsmp4
Watch a video about the habitats and characteristics of sloths, the slowest mammals on earth.

Adults weigh about 6 pounds and are the size of a skunk. Pygmy sloths live on a small island, about 10 miles off the coast of Panama. Smaller-than-average brown-throated sloths live on some of the nearby islands. So for a long time when scientists came across a pygmy sloth, they thought it was a young brown-throated sloth.

Like other sloths, pygmy sloths are not known for their speed on land. On average, sloths travel at most 120 feet per day. In the water, however, these Muppet-like mammals can swim at speeds about three times their pace on land. “I was impressed by how capable and graceful they were in the water!” says Becky Cliffe. Cliffe, a zoologist from the United Kingdom, has spent the past five years researching sloths. It takes a lot of patience and hard work to study these slow-moving creatures.

Jim McMahon/Mapman

THE SLOW LIFE

Sloths live in the rainforests of Central and South America. They have long arms like monkeys but are actually related to anteaters. There are six species of sloths, which fall into two categories: three-toed sloths and two-toed sloths. They spend nearly all their time hanging from the upper branches of the highest trees in the rainforest, known as the canopy. They move so slowly that algae grow on their fur.

Sloths aren’t slow just when it comes to moving. It can take a whole month for a sloth to digest a single leaf. But this laid-back pace can be a lifesaver. Sloths often eat leaves that are toxic. If they were to digest the leaves too quickly, the sloths could be poisoned. Because it takes such a long time to break down dinner, a sloth can spend more than half its day resting as it digests.  

Suzi Eszterhas/Minden Pictures

STUDYING SLOTHS

Sloths are masters of camouflage. They sleep and keep still during the day. The green algae in their fur helps them blend into the forest canopy they call home. Spotting a sloth in the wild is tough work, but the rainforest itself also poses its own challenges to scientists studying them.

“It’s full of snakes, spiders, scorpions, bullet ants, and hairy caterpillars, just to name a few! All of which can cause some serious problems,” says Cliffe. 

The challenges of observing sloths is one of the reasons we know so little about them. But Cliffe is working to change that. Her research has shed some light on the lives of sloths (see Sloth Backpack Project). “It is only in recent years that we are beginning to see just how the sloth lifestyle is an incredibly successful survival strategy,” says Cliffe. “They are stealthy rather than lazy.”

AN UNCERTAIN FUTURE

Pygmy sloths’ habitat is threatened. The trees they live in are being cut down to make space for farms, roads, and houses. At least 1 acre of rainforest is cleared every second. Given sloths’ slow lifestyle and specialized diet, they don’t adapt well to rapid changes in their environment.

Although the pygmy sloth is the most endangered sloth species, it’s not the only sloth species that’s in trouble. The maned sloths of Brazil are also listed as vulnerable. “From power line electrocutions and dog attacks to road collisions, deforestation, and human cruelty—it is a long and sad list of threats,” says Cliffe. 

Rainforest destruction threatens many other plants and animals too. Cliffe says even little actions, like supporting local farmers and eating less meat, can help save the rainforest. These changes reduce the need to cut down the rainforest for farmland and livestock grazing.

For Cliffe, the challenges of her slow-paced research are worth it. “Working hands-on with sloths is truly magical,” she says. “I have a real opportunity to learn more about these unusual animals and use the information to make a positive difference.”

Find unit rates to compare the speed of sloths and other creatures that live in Central and South America’s rainforests. Round all answers to the nearest hundredth. Record your work and answers on our answer sheet.

Moving at its top speed, a sloth would take 20 hours to go 3 miles on land. What’s that in miles per hour?

It would take a sloth 130 minutes to swim 1 mile. What’s that in miles per hour?

Sloths climb through the canopy while hanging upside down. If it takes a sloth 10 minutes to climb 7.5 feet, what’s its climbing speed in miles per hour?

Jaguars are one of a sloth’s predators. At top speed, a jaguar can run 2.5 miles in 3 minutes. What’s its speed in miles per hour?

Jaguars are agile swimmers. If a jaguar were to go 2,600 feet in 15 minutes, how fast did it swim in miles per hour?

A jaguar was recorded climbing a 25-foot-tall tree in 6 seconds. What was its speed in miles per hour?

At top speed, an Amazon river dolphin can swim 6 miles in 30 minutes. What is the river dolphin’s speed in miles per hour?

A. If a river dolphin, jaguar, and sloth each swim the same 4 miles, how long would it take each animal to swim that distance?

B. How much faster was the fastest animal than the slowest animal in hours and minutes?

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