Sloths are the very picture of slowness, but when it comes to record-breaking underwater breath-holding, slowness is the last they’re thinking about. With a record of up to 40 minutes underwater, sloths amaze and even surpass the dolphin at this unexpected skill. Moving through the woods at their own slug’s pace, underwater they reveal an unsuspected competence that is of biological interest and evolutionarily clever.
How sloths survive by slowing down nearly everything
One of the main reasons sloths are able to remain underwater for as long as they do is because of their very slow metabolism. It’s not just some fascinating piece of trivia—there’s a survival mechanism involved. Their diet of low-calorie leaves means that their bodies are not expending energy anywhere close to the rate other mammals do. The lower the energy they expend, the lower the oxygen they consume, and it’s this that accounts for the breath-holding endurance.
Even more incredible is that sloths can slow the rate of their heart by nearly 90% when underwater. That’s right: oxygen-rich blood circulates slower and more efficiently through their bodies, giving them a staggering amount less time to have to return to the surface. Translate it to human language, and it’s like putting your body in an ultra-low-power mode. This process isn’t just cool—it’s critical for avoiding predators in the wild.
Sloths are surprisingly good swimmers in tropical rainforests
Although living most of their lives inverted in the treetops, sloths are buoyant and good swimmers. Tropical rain forests tend to flood during the wet season, and rivers are natural arteries running through thick jungle. When sloths actually do swim, they paddle rather effectively if slowly with a form of dog paddle and are actually very elegant.
The ability to hold its breath is particularly useful in these swims. In case there is someone lying in wait for them—either on the ground or in the treetops—sloths can inch into the water, swim under, and remain underwater, motionless for extended periods of time. Since they possess gas-filled digestive tracts, which provide buoyancy, and low metabolic requirements, sloths are perhaps the sneakiest rainforest aquatic mammal despite not being even aquatic animals themselves.
Sloths vs dolphins: a comparison that no one anticipates while holding their breath
It is hard to believe, but sloths hold their breath underwater four times longer than dolphins. While dolphins normally sustain around 10 minutes without water, sloths easily reach 30 to 40 minutes. The reason for this surprise comparison is straightforward: dolphins are living creatures that swim very fast and are always moving. They need enormous oxygen supplies in order to perform their agile movements and fast reflexes.
Sloths, on the other hand, are masters of doing absolutely nothing. Their low heart rate and rate of movement mean they just don’t need as much oxygen. That enables them to stay underwater for a whole lot longer. What it does to dolphins, sloths manage by exercising cautious restraint. It’s one that living in the wild is never about being fast—sometimes it’s about staying still being the ultimate power play.
Standing still is saving lives in a predator-filled world
This aquatic skill isn’t simply a cool biological quirk—it’s a survival mechanism for the sloth. In Central and South America’s rainforests, up and down might be fatal. Harpy eagles have the eyesight of an eagle and can see movement far above, and jaguars prowl the ground. By freezing in position, or simply remaining submerged, sloths can avoid both of them safely.
It is an existence that has been refined by millions of years of evolution, crafting sloths as some of the most energy-conservative beings on the planet. Their camouflage skill, paired with their remarkable breath-holding capability, enables them to turn invisible to the eye when necessary. It is a stealth mode unlike any other.