Slowest Animals in the World: Sloths, Snails and Sea Stars

How slow is slow? Measuring the slowest animals

Speed records for slow animals are harder to find than for fast ones, because few scientists time a snail. The figures below come from measurements in the wild or in laboratories and are typical speeds, not exact records. Animals that do not move at all as adults, such as sponges, corals and barnacles, are left out. Sea anemones are borderline: most stay put, but some can glide very slowly on their sticky base.

1. Dwarf seahorse: about 1.5 m (5 ft) per hour

Guinness World Records lists the dwarf seahorse (Hippocampus zosterae) as the slowest-moving fish, with a top speed of about 1.5 m (5 ft) per hour. It is tiny, usually 2–2.5 cm (about 1 in) long, and lives in shallow seagrass beds in Florida, the Gulf of Mexico, the Bahamas and Bermuda. Like all seahorses, it swims upright, pushed by a small fin on its back that flutters very fast, while the body hardly moves. Instead of chasing food, it clings to seagrass with its tail and waits for tiny animals to drift past.

2. Garden snail: a few meters an hour

The garden snail crawls at roughly 1–2 mm per second, or about 4–7 m (12–24 ft) an hour, depending on the surface and conditions. It moves on a single muscular foot: waves of contraction ripple along the underside while a layer of mucus lets it grip and glide at the same time. The best-known racing record belongs to a snail named Archie, which covered a 33 cm (13 in) course in two minutes at the World Snail Racing Championships in England in 1995.

3. Banana slug: up to 17 cm (6.5 in) per minute

The Pacific banana slug of the forests of western North America is the second-largest land slug in the world, reaching up to 25 cm (9.8 in) long. It can move at about 17 cm (6.5 in) per minute, or roughly 10 m (33 ft) an hour. Its thick coat of slime keeps it from drying out and makes it unpleasant for most predators to eat.

4. Sea stars: centimeters per minute

Sea stars walk on hundreds of tiny tube feet, worked by water pressure inside the body. Most species manage roughly 10–30 cm (4–12 in) per minute; a study of four Indo-Pacific species measured average speeds of about 8–46 cm (3–18 in) per minute. The fast exception is the sunflower sea star of the North Pacific, which can cover about 1 m (3.3 ft) a minute. The ochre sea star of North America’s Pacific coast moves slowly but is a powerful predator of mussels, which it pries open with its arms.

5. Three-toed sloths: about 0.24 km/h (0.15 mph)

Three-toed sloths such as the brown-throated sloth are usually named the slowest mammals. In the trees they move at about 0.24 km/h (0.15 mph), or around 4 m (13 ft) a minute, and many travel less than 40 m (130 ft) in a whole day. They eat leaves, which give little energy, and their metabolism runs at about half the rate expected for a mammal of their size. The full explanation is in why are sloths so slow?

6. Two-toed sloths: slow, but a little busier

Two-toed sloths, such as Hoffmann’s two-toed sloth, are slightly larger and somewhat more active than their three-toed cousins, and they eat more fruit and flowers. They are still slow climbers that hang upside down for most of their lives, and they are active mainly at night. On the ground both kinds of sloth are clumsy, but both are surprisingly capable swimmers.

7. Giant tortoises: about 0.3 km/h (0.2 mph)

Galápagos giant tortoises have been observed walking at about 0.3 km/h (0.2 mph). With a heavy domed shell, and large males weighing more than 250 kg (550 lb), they have little reason to hurry: adults have no natural predators. They also have very slow metabolisms and can live for well over 100 years in the wild.

8. Slow lorises: deliberate climbers

Slow lorises are small, big-eyed primates of the tropical forests of South and Southeast Asia. They creep through branches hand over hand at night, rarely leaping, and can freeze for long periods when disturbed. They are the only primates known to have a venomous bite, produced by mixing a secretion from a gland on the upper arm with saliva. Every slow loris species assessed by the IUCN is threatened, mainly by habitat loss and the illegal pet trade.

9. Greenland shark: the slowest swimmer for its size

The Greenland shark lives in the cold North Atlantic and Arctic Ocean and grows to well over 4 m (13 ft). Tagged sharks swam at an average of only 0.34 m per second, about 1.2 km/h (0.76 mph), with a fastest cruising speed of about 0.74 m per second, around 2.7 km/h (1.7 mph). Its slow pace matches its slow life: a 2016 study estimated that Greenland sharks can live at least 272 years, the longest lifespan known for any vertebrate. See how slow is a Greenland shark?

10. Manatees: 5–8 km/h (3–5 mph)

Manatees are slow for marine mammals, usually cruising at 5–8 km/h (3–5 mph), although they can reach about 30 km/h (20 mph) in short bursts. They graze on seagrass and other water plants and have a low metabolic rate for their size. Their unhurried life in shallow water makes collisions with boats one of the biggest threats to the West Indian manatee in Florida.

11. American woodcock: the slowest bird in flight

The American woodcock, a plump, long-billed shorebird of eastern North American forests and fields, holds the record for the slowest flight speed measured for a bird, about 8 km/h (5 mph). On migration it flies much faster, at around 26–45 km/h (16–28 mph). On the ground it is famous for a slow, rocking walk.

Sleepy rather than slow: the koala

The koala is often called lazy, but it can move quickly when it needs to. It simply rests a lot: koalas sleep or rest for up to about 20 hours a day. Their diet of eucalyptus leaves is low in energy and hard to digest, and their metabolic rate is only about half that of a typical mammal, so long rests save energy, the same trade-off that shapes the sloth.

Why being slow works

Slowness is not a failure of evolution but a successful strategy:

• Saving energy: leaf-eaters such as sloths and koalas live on a low-energy diet, and slow movement keeps their energy costs low.
• Staying hidden: predators such as harpy eagles and big cats often spot prey by movement, so a sloth that barely moves is hard to see.
• Armor and defenses: shells protect snails and tortoises, slime protects slugs, and the slow loris has its venomous bite.
• Cold bodies: cold-blooded animals in cold water, like the Greenland shark, have slow muscles and slow metabolisms.
• Waiting instead of chasing: seahorses and sea anemones let food come to them.

Many slow animals also live long lives, from giant tortoises to Greenland sharks. For the other end of the scale, see the fastest animals in the world.