Summary: Sloths are often quiet, but not completely silent. Their rare calls tell us a lot about baby care, mating, stress and why calm habitats matter.
Sloths have a reputation for being slow, sleepy and almost silent. That is mostly fair. A sloth is not trying to fill the rainforest with chatter. It saves energy, keeps still, blends into leaves and usually has very little reason to announce itself.
But silent does not mean soundless. Sloths can call, hiss, moan and cry in particular moments. The interesting part is how rarely they do it. Their sounds are not background noise. They are small, important signals used when a baby needs its mother, when an adult is distressed, or when a potential mate needs to be found through a tangle of rainforest leaves.
Most adult sloths are quiet by design
The Smithsonian National Zoo describes two-toed sloths as mostly silent animals. That fits the rest of their lifestyle. Two-toed sloths spend most of their time in the rainforest canopy, rely heavily on camouflage, and have a much lower metabolic rate than would be expected for a mammal of their size.
For a canopy animal that moves slowly and eats a low-energy diet, being noisy would not always be useful. Sound can reveal location. Stillness, greenish fur, slow movement and a calm routine are often better defenses than making a scene. When threatened, Smithsonian notes that two-toed sloths may defend themselves with claws and teeth, but their first strategy is usually to avoid being noticed at all.
Distress sounds are the exception, not the everyday rule
Quiet animals still need a way to say something is wrong. Smithsonian says distressed two-toed sloths may make hissing sounds or low moaning cries. Animal Diversity Web's Hoffmann's two-toed sloth account also describes these sloths as generally silent, while noting that they may hiss when highly stressed or agitated.
That distinction matters. A sloth sound is not a cute party trick. It can be a welfare clue. If a normally quiet animal is hissing, moaning or making repeated distress calls, something in its environment may be too close, too loud, too frightening or too difficult to escape.
Baby sloths use calls to stay connected
For young sloths, sound can be a lifeline. Animal Diversity Web notes that when an infant Hoffmann's two-toed sloth is separated from its mother, it can give a loud, low-pitched distress call lasting 30 to 90 seconds. The same source explains that young sloths are born with claws and cling to their mother soon after birth.
That makes sense when you picture life high in the canopy. A baby sloth is not just riding along for comfort. It is learning food routes, body positions, grip and the pace of a life lived among branches. If separation happens, a contact or distress call helps restore the most important relationship that baby has.
Animal Diversity Web's three-toed sloth overview makes a similar point for Bradypus sloths, saying vocal communication with offspring is important during infant dependence. Even in an animal known for solitude, the mother and baby bond has its own small language.
Mating can be louder than people expect
Sloths are solitary for much of their lives, so finding a mate is not as simple as bumping into one at speed. Animal Diversity Web reports that female Hoffmann's two-toed sloths may use a high-pitched scream to advertise readiness to mate. Males can then move toward the female, and if more than one male arrives, conflict may follow.
This is one of those facts that feels almost funny because it breaks the stereotype. The animal famous for stillness can, in the right moment, make a sound designed to travel. The point is not that sloths are secretly noisy. It is that their communication is selective. They spend most of their time quiet, then use sound when the cost is worth it.
Noise around sloths deserves more respect
Understanding sloth sound also means thinking about what sloths hear. A 2023 study published in Animal Welfare looked at Linnaeus's two-toed sloths in a walk-through zoo enclosure and found that visitor-associated noise was linked with behavioural changes. The authors suggested that walk-through enclosures for sloths may need better acoustic management, such as controlling visitor numbers or adding sound barriers.
The study was small, so it should not be stretched into a sweeping claim about every sloth in every setting. But it supports a simple, kind idea: animals adapted for slow, quiet canopy life should not be treated like props in a noisy room. Calm space, distance and choice matter.
The takeaway for sloth lovers
Sloths are not mute. They are careful. Their sounds are saved for moments that matter: a baby calling for its mother, an adult warning that it is distressed, or a mate call crossing the leaves.
That makes them even more interesting, not less. The famous sloth calm is not laziness. It is an energy-saving strategy shaped by canopy life, camouflage, diet and survival. The best way to love sloths is to respect that quietness, support habitat protection, avoid exploitative handling experiences and give these animals the slow, leafy space their bodies are built for.
Image: Dave Pape, Wikimedia Commons, Public domain. Featured image source: Wikimedia Commons.
