Crabs are fascinating creatures that have captured people’s imaginations for centuries. Their unique sideways walk and powerful pincers make them instantly recognizable. But just how fast can these crustaceans move?
If you’re looking for a quick answer, here it is: Most crabs walk at a speed of about 10 body lengths per minute. However, some species can walk significantly faster or slower than this.
In this comprehensive article, we’ll take an in-depth look at crab speeds. We’ll discuss the factors that influence how fast crabs can walk, look at speed variations between crab species, and compare crab speeds to those of other animals.
Anatomy and Physiology of Crabs
Basic Crab Anatomy
Crabs have a unique body shape and structure that sets them apart from other crustaceans. Their bodies are broad, flattened, and divided into three main parts – the cephalothorax, abdomen, and claws (The unique body structure of crabs allows them to inhabit various aquatic environments).
The cephalothorax is the front part of the crab where its head and thorax are fused together. This section contains the crab’s eyes, mouthparts, brain, and stomach. The abdomen is tucked under the cephalothorax.
Crabs have five pairs of legs for walking, swimming, and grasping food. The front pair of legs ends in claws or pincers, which crabs use for defense and to tear food apart. Male crabs tend to have larger claws than female crabs.
How Crabs Move
Crabs generally move in a sideways direction by coordinating the motion of their legs (The unique sideways movement helps crabs inhabit narrow spaces). Their legs are arranged differently on each side of their body allowing for this type of motion.
Crabs have specially adapted feet to match the terrain and conditions of their environment. For example, tree crabs have pointed feet for grasping bark, whereas marsh crabs have webbed feet for maneuvering wet sand. This allows crabs to adeptly move on land, in water, or near shorelines.
While crabs prefer to move sideways, they can move forwards and backwards if needed. To go forward, a crab moves its back legs first, then its front legs. Crabs can also swim short distances by using paddle-like motions with their back legs (The ability to swim also allows crabs to migrate or escape predators if required).
Speed varies significantly among the over 4,500 species of crabs. Smaller crabs, like pea crabs, can run up to 4 meters per minute. Larger crab species, like the Atlantic ghost crab, have been recorded moving at speeds of over 2 miles per hour.
| Crab Species | Average Speed |
| Pea Crab | 4 meters per minute |
| Fiddler Crab | 0.3 meters per second |
| Atlantic Ghost Crab | 3 kilometers per hour or 2 miles per hour |
In comparison, a typical human can sprint at around 15 miles per hour. So while not the fastest creatures, crabs can scuttle along at a decent pace!
Factors That Influence Crab Speed
Leg Length
Crabs with longer legs, spanning a larger leg diameter, tend to move faster than crabs with shorter legs. The ghost crab, which inhabits sandy beaches around the world, is known for its long legs and ability to dart quickly across the sand at speeds up to 10 mph.
In contrast, smaller crabs like hermit crabs and pea crabs move at much slower paces with their shorter legs.
Body Size
In addition to leg length, the overall body size of a crab impacts how fast it can move. Smaller crabs need to move quickly to avoid predators, finding food, and locating new shells as they grow. Tiny pea crabs measure just a few millimeters wide but can swim rapidly to find food or new hosts.
Larger king and snow crabs trade speed for their formidable size and thick shells that deter predators.
Species
Some crab species have physical traits and behaviors specifically adapted for speed. Mud crabs and land hermit crabs have powerful claws for quick movement across muddy beaches and coastal terrain. Spider crabs are aptly named for their ability to use their long, spindly legs to swiftly climb vertical surfaces.
Swimming crabs like blue and paddle crabs have specially shaped rear legs to paddle quickly through the water.
Temperature
Crab activity and speed is directly related to ambient temperature. Crabs are cold blooded, so they move faster in warm environments and drastically slow down in cold temperatures. According to a 1983 study, the movement rate of fiddler crabs nearly quadrupled as temperatures rose from 59°F to 86°F.
This suggests that global warming may increase crab speeds over time.
Environment
A crab’s habitat impacts how quickly it can move around. Aquatic crabs like blue crabs navigate currents and waves that affect their swimming pace. Beach crabs can bolt rapidly across open sand flats but need to move slower over rocky, uneven terrain.
Tree-climbing coconut crabs leverage their strong claws to quickly scale palm trees and wooden structures in their island environments.
Speeds of Different Crab Species
Fiddler Crabs
Fiddler crabs, with their single oversized claw, are a familiar sight scurrying along sandy beaches and mudflats. Though small, usually around 2 inches across, these little crustaceans sure can move! Fiddler crabs can sprint at speeds up to 2.5 feet per second when they need to escape predators or scavenge for food.
Their legs are perfectly adapted for quick bursts across open ground. Wow, imagine if we could run 15 miles per hour like a fiddler crab! 🦀
Ghost Crabs
The ghost crab is aptly named for its ability to dash swiftly across the beach, as if a phantom in the night. Growing up to 4 inches wide, ghost crabs have long, spindly legs built for speed. In fact, these sandy-colored crabs can scramble at up to 10 feet per second in short bursts.
Their top speed allows them to hunt for food and avoid threats effectively. While not as fast as a cheetah, nearly 7 mph is mighty impressive for a crab! 😲
Hermit Crabs
As anyone who’s kept hermit crabs as pets knows, these little crabs don’t go racing around their tanks. Hermit crabs occupy shells vacated by other animals and carry their shelter with them as they crawl. Depending on species, hermit crabs amble along at 0.1 to 0.7 feet per second.
Their shell and soft abdomen limit rapid movement. But what hermit crabs lack in speed, they make up for in charm! 🥰
King Crabs
The largest crab species, king crabs have leg spans over 5 feet across. However, these giants of the crab world aren’t known for their speed. Their massive claws are slower and more powerful, adapted for prying open hard-shelled prey.
King crabs lumber across the seafloor at just 0.5 feet per second on average. But with their intimidating size and strength, king crabs hardly need to move fast to find food or defend themselves. 🦞👑
Snow Crabs
With their spindly legs and light bodies, snow crabs can scuttle surprisingly quickly along the ocean bottom. They sprint short distances at up to 1 foot per second to evade predators or snatch up food.
While not the speediest of crabs, snow crabs are definitely faster than their hefty king crab cousins. And those long legs can propel them rapidly backwards to escape danger in a pinch! 🦀❄️
How Do Crab Speeds Compare to Other Animals?
Mammals
Crabs move at a much slower pace than most mammals. The fastest human sprinters can reach over 27 mph, while thoroughbred horses have been clocked at 43 mph. In comparison, even a quickly scuttling crab moves at just 1.6 feet per second, or roughly 1 mph.
Land mammals have the advantage of stride length and rapid leg movement to build momentum.
Reptiles
Reptiles like lizards and snakes typically move faster than crabs. For example, the Costa Rican zebra-tailed lizard can sprint up to 21 mph to escape predators. However, some turtles and tortoises have top speeds comparable to a crab’s pace. The marginated tortoise travels at around 0.7 mph.
So while crabs cannot match the bursts of speed from reptiles, they keep pace with some of the slower species.
Other Crustaceans
Crabs are certainly not the speed demons of the crustacean world. Smaller crustaceans like krill and copepods can swim rapidly by beating their appendages, reaching speeds of 70-90 body lengths per second, according to one study.
Larger crustaceans like lobsters and shrimp rely less on speed, but can sprint faster than crabs off the sea floor using tail flips. So crabs rank on the slower side of crustaceans due to their sideways walk.
Insects
| Insect | Top Speed |
| Cockroach | 3 mph |
| Tiger beetle | 5.6 mph |
In terms of speed, crabs generally move slower than many common insects. For instance, a crab’s top pace is comparable to a cockroach’s typical scampering speed. However, the fastest insects like tiger beetles can sprint at up to 5.6 mph, over 3 times faster than a sprinting crab.
Insects have six rapid legs for movement and can cover over 100 body lengths per second at top speed. So when it comes to speed, crabs lag far behind many bugs.
Conclusion
Crabs come in all shapes and sizes, so their speeds vary greatly across species. But while some can sprint rapidly on the beach, most crabs tend to move at a more moderate pace of about 10 body lengths per minute.
Their specialized anatomy allows these iconic crustaceans to scuttle sideways with ease. Understanding the factors that impact crab speed gives us a deeper appreciation of these fascinating creatures.
