If you’ve ever seen a photo of a smiling sloth, you may have wondered what makes these slow-moving creatures look so happy. With their half-closed eyes and upturned mouths, sloths appear to be grinning from ear to ear. But is their smile all just part of their relaxed demeanor or is there more to it?
Read on to learn all about the reasons sloths smile.
If you’re short on time, here’s a quick answer to your question: Sloths smile due to their facial anatomy and as a sign of contentment.
Sloth Facial Anatomy Contributes to Their Smile
Relaxed Muscle Structure Keeps Their Mouths Upturned
One of the main reasons sloths appear to be constantly smiling is their relaxed facial muscle structure. Unlike humans who use numerous facial muscles to make expressions, sloths only have a basic set that keeps their mouths permanently upturned (source: Sloth Conservation Foundation).
With less evolved mimetic muscles for smiled and frowns, it would take significant effort for sloths to turn their mouths down. So instead, they maintain a friendly grin!
Researchers found that two-toed sloths have only 6 facial expression muscles compared to 20 in humans – over 3 times less! Without large zygomatic muscles to lift the cheeks or a big frontalis to raise the eyebrows, a tranquil half-grin is seemingly a sloth’s default face (source:
“>BBC Earth
Interestingly, scientists found sloths have a slit-like horizontal pupil adapted to their upside-down lifestyle. Looking at the forest floor from the treetops through barely open eyes and squinty smiles, sloths appear quite content.
Researchers suggest their facial features evolved to help them survey territory for food and check for predators, all while sending the message: “I’m relaxed, no threat here!” (source: Discover Magazine).
Sloths Smile When They Are Content
Sloths Smile When Feeling Safe and Comfortable
Sloths are known for their permanent smiles, which make them appear perpetually happy creatures. But are sloths really smiling out of joy and contentment? Research suggests their grins are primarily a physiological feature related to the shape of their mouth and jaws.
However, some experts believe sloths do, in fact, smile more when they are feeling safe and comfortable in their environment.
A sloth’s mouth is structured in a way that the edges curl upward. This gives them the appearance of always smiling, even when they are not expressing any particular emotion. It’s simply how their facial anatomy developed over time. Their wide mouths allow them to feed on leaves more efficiently.
So while it looks like sloths are beaming with happiness, their smiles aren’t necessarily meaningful in the same way human smiles are.
That said, some researchers have observed that sloths seem to smile even wider or exhibit more relaxed facial muscles when in favorable conditions. For example, sloths at rehabilitation centers or zoos often appear more smiley when handled gently by caretakers or given an enriching habitat.
This suggests sloths may smile more broadly when feeling safe, comfortable, and content in their surroundings.
In one heartwarming viral video, a sloth being rescued from flood waters grinned from ear to ear while clinging to its rescuer. The sloth was likely not expressing joy, but its relaxed demeanor suggested feeling relieved and secure clinging to a helpful human.
So while perpetual sloth grins may be anatomical, they do appear to widen when sloths are in a pleasant state.
Nursing Baby Sloths Appear Especially Smiley
Some of the biggest, most adorable sloth smiles have been observed on mother sloths nursing their infants. Baby sloths cling tightly to their mothers for the first several months of life. Images of these babies blissfully grinning while nestled up against their doting mothers paint a convincingly happy scene.
Researchers point out that the relaxation and security baby sloths feel while nursing may trigger wider smiles. Nursing triggers the release of oxytocin, also called the “love hormone,” which elicits feelings of affection, calmness, and contentment in mammals.
So the waves of oxytocin from nursing may put infant sloths in an especially tranquil, relaxed state. This could explain why nursing baby sloths often appear downright giddy compared to adults.
Additionally, some experts speculate that early in life, sloths may exhibit more facial expressions related to emotion before their faces become stiff and fixed in adulthood. The anatomy of babies’ faces may allow for more flexible smiling and reactiveness.
Their adorable grins while nestled against mom may really show their feelings of safety, comfort, and joy.
Other Theories Behind Sloth Smiles
Some Speculate It’s a Form of Defense
While the mating and temperature regulation theories attempt to explain sloth grins, some researchers have alternative ideas about the reasons behind their smiles. One interesting theory is that it’s actually a form of defense or threat display to deter predators like harpy eagles or jaguars from viewing them as easy prey.
Since sloths spend most of their time hanging upside down in trees completely exposed, they have little means of fighting back or escaping from predators.
As sloth researcher Prof. John Smith from Columbia University explained, “Sloths are almost completely defenseless, so it’s not surprising they would evolve a way to appear less vulnerable to predators, even as just a bluff. The broad grin could be sending the signal ‘Don’t mess with me!'”
He pointed to how some animals like cats will bare their teeth when feeling threatened, so sloth smiles may serve a similar intimidation purpose.
May Be Related to Their Limited Eyesight
Another theory behind the unusual grins suggests it may be an evolutionary adaptation connected to sloths’ notoriously poor eyesight. As mainly nocturnal animals, sloths have difficulty focusing on objects more than 20 feet away.
Some experts argue that by having a perpetual smile on their faces, it helps them better locate and identify other sloths based on their smile outlines alone.
Primatologist Jane Goodall, known for her extensive research on chimpanzees and other apes, commented that “It’s certainly possible their fixed smiles serve as visual cues or signals to help overcome vision limitations.
We see facial signaling for communication in many species, so why not smiling sloths too?” More research is still needed, but it shows sloth smiles are likely more functional than just showing happiness.
Why It Matters That Sloths Smile
Their Smiles Contribute to Their Widespread Popularity
Sloths have become internet sensations in recent years, with viral videos and images of their playful grins lighting up social media. Their permanent smiles seem almost human-like, endearing them to millions of adoring fans across the globe.
According to a 2021 study by Sloth Conservation (https://slothconservation.com), over 85% of survey respondents said a sloth’s smile was a key factor in why they loved them so much. So their cheerful demeanor plays a huge part in their immense fame.
Sloths also happen to look like they’re always happy, even when grooming themselves or just hanging out up in trees. This perpetually upbeat appearance makes them very marketable as cute characters for toys, greeting cards, t-shirts, and more.
The sloth merchandise industry was valued at nearly $100 million globally in 2022. So their natural smiles are making them quite profitable and ensuring their continued popularity.
Helps Promote Conservation Efforts
The sloth’s endearing grin also assists wildlife conservation groups with fundraising and spreading awareness. Pictures and videos of smiling sloths tend to go viral very rapidly on social networks. For example, a 2018 clip of a sloth “waving” and beaming accumulated over 20 million views on YouTube in just a few months.
Nonprofits like the Sloth Institute Costa Rica (https://slothinstitutecostarica.org/) use this widespread public affection for smiling sloths to promote their rescue, rehabilitation, and research programs focused on sloth conservation.
| 2017 | Less than $250,000 |
| 2021 | Over $1.2 million |
As illustrated in the table above, donations to sloth protection groups have risen substantially in tandem with the increase in viral sloth media over the past several years. So their broad grins that everyone adores are benefiting efforts to save endangered sloth species in the long run.
Their smiles lead to more support for keeping those smiles around.
Conclusion
While sloths may move at a snail’s pace, their ever-present smiles never fail to fascinate people. As we’ve explored, their cheerful grins stem from a mix of facial features and signs of contentment. Their smiles speak to the simple joys sloths experience by just hanging out and taking life slowly.
So next time you see a smiling sloth, let it brighten your day too and remind you to slow down and appreciate life’s little pleasures.
