Sloths Can Hold Their Breath Longer Than Dolphins

The remarkable ability of a sloth to remain submerged underwater for up to 40 minutes is a fascinating byproduct of its famously slow-paced lifestyle. This incredible feat, which surpasses the 8 to 10-minute breath-holding capacity of dolphins, is not due to large lungs but rather to an exceptionally slow metabolism. A sloth's diet of low-nutrient leaves necessitates a low metabolic rate to conserve energy, a trait that extends to its respiratory and circulatory systems. When underwater, a sloth can further slow its heart rate to about one-third of its normal pace, drastically reducing its oxygen consumption.

This physiological adaptation proves to be a crucial survival mechanism. Inhabiting rainforests that are often interspersed with rivers and prone to flooding, sloths are surprisingly adept swimmers. They can move up to three times faster in water than on land, using their long limbs to paddle efficiently. The ability to hold their breath for extended periods allows them to traverse these waterways to find new food sources or mates and to evade predators.

Interestingly, the same slow digestion that contributes to their energy-conserving metabolism also aids their aquatic prowess. The large, multi-chambered stomach of a sloth, filled with slowly fermenting leaves, can account for up to a third of its body weight. This gas-filled digestive tract acts as a natural flotation device, helping the sloth to remain buoyant and swim with greater ease. Therefore, the very characteristic that defines the sloth's sluggishness on land becomes a key asset in the water (Review).