Crabs are known as spiders of the ocean and have compound eyes made up of tiny lenses. Crabs have 10 legs, and most crabs have flat bodies, making it easy for them to move between rocks. The largest crab can reach 13 feet in size. If you’ve seen a crab walking along the shore, you’ve probably noticed that they walk sideways, but why do crabs walk sideways?
Crabs walk sideways because their knees bend outwards, making them walk sideways. Crabs have stiff jointed legs, and walking sideways means one of their legs never crosses another leg while walking. If crabs had to walk any other way, they might trip over their legs.
When crabs walk, they use a pull and push motion. They pull with one set of legs and push with another. This is hard work for a crab because they must balance their claws and walk simultaneously. The average lifespan for a crab is between 3 and 4 years, but species like the Japenese Spider crab have been known to live to 100 years old.
What Makes Crabs Walk Sideways?
Crabs are found in tropical regions worldwide. The heaviest crab ever found was a King crab which weighed 28 pounds. Crabs are shielded with an exoskeleton to protect themselves. Crabs shed their exoskeleton once a year to allow them to get bigger.
Crabs have a wide and flat body which helps them bury themselves in the sand and squeeze between narrow rocks. Their shape also restricts the shoulder joint in their legs, giving them a restricted range of motion. As a result, some crabs can move slowly; however, most walk sideways. Crabs have 10 legs but mainly use 8 of them to walk, while the other two generally have claws and are used to protect them.
Crabs can also walk backward and diagonally. Crabs have 5 pairs of legs attached to each side of their body. Having their legs on either side of their body works with their shape to help them move around more easily.
Most crabs have front legs with claws, mainly used to grab food and fight predators. A crab’s shell also limits their range of movement at their hip joints, so they must rely on their knee joints to move them around.
Because crabs spend most of their time under rocks and sand, they have evolved and developed a thick bodies with flexible joints. This allows them to quickly move through difficult narrow rocks and easily bury themselves in the sand to escape predators.
Crabs don’t need to walk straight when they move more quickly when walking sideways. As scavengers, they don’t necessarily need to be fast to hunt for food but just to be able to escape predators. Being able to hide and bury themselves in the sand is more beneficial to a crab than being able to move quickly or walk forwards.
When crabs walk sideways, the most vulnerable parts of their body remain protected, like their eyes and antenna. However, crabs can only walk in one direction sideways and can’t walk from left to right sideways. This is due to the structure of their joints.
Do Crabs Only Walk Sideways?
Crabs can also move forwards, backward, and diagonally and are not just limited to moving sideways. Most crabs walk sideways because of their body shape and the joints in their legs which make them move in this way. However, some crab species have longer bodies and are known to walk forwards and not sideways.
Crabs like the Fiddler crab only move sideways, and they are speedy. When the fiddler crab feels threatened, it will scurry off in a hurry in the blink of an eye. In fiddler crabs, sideways walking and
running isn’t something they just do to move around but is part of their mating ritual too.
Crabs can move slowly forward but move quicker sideways when using the second joint in their leg. These joints are simply constructed and help a crab walk sideways.
Like the stone crab, most crabs can walk and run across the bottom of the ocean. In addition, some crabs have legs called swimmerets, allowing them to swim through the sea.
Do All Crabs Walk Sideways?
Not all crabs walk sideways. Some crab species move forward because they have long bodies, not wide ones. A few of these species include the Libinia Emarginata and the Raninids. A soldier crab is one species of crab that mostly moves forward.
The soldier crab has an egg-shaped body which differs from most crabs which have a more elongated body. The leg joints in a soldier crab allow the crab to move at bigger angles and will enable the crab to move forward.
Hermit crabs are another species of crab that can walk forwards and backward. The hermit crab’s legs can bend backward and forwards instead of sideways. Sometimes hermit crabs drag their belly across the sand as they move around.
Decorator crabs are another species of crab that don’t walk sideways. Instead, decorator crabs have a round, pear-shaped body, and they walk forwards instead of sideways. Crabs like the coconut crab climb trees to find food and have gone through many adaptations.
Do Crabs Walk Sideways With Other Crabs?
Crabs are solitary creatures, and most species prefer being alone. However, some species of crabs live in groups. Crabs that live in groups move around together and find a mate more easily. These crabs often walk sideways across the ocean floor or on land.
At times social crabs can also be found being solitary. Hermit crabs, despite their name, are not solitary crabs. These crabs live in colonies with over 100 other crabs. They sleep together and move around together. Its safer for crabs to live in a group, and predators are less likely to attack crabs living in a group.
Do Crabs Walk Sideways When Underwater?
Crabs are found in oceans and in freshwater. Some crabs live on land but can also live in burrows in the sand and in mud. Most crabs spend most of their time on the ground, and some may even go several hours without returning to the water. Other crabs live on the shore and may just touch the water’s surface to get oxygen and keep their gills wet.
Crabs can survive outside the water if their gills are kept moist. Most crabs don’t move sideways underwater but use their claws for swimming. Not all species of crabs can swim, only some. Crabs live in different places but love cold and dark areas, which help keep their gills moist.
Some crab species run across the ocean floor, either forwards or sideways.
The crabs on land can get water from their food and the habitat around them, which they can store in their body’s bladder, blood, and other compartments. This makes it easier for them to go without water for extended periods.
During the day, crabs sleep under the sand or spend most of their time hiding. At night, crabs are awake and look for food, mate, and keep away from the heat during the daytime. When crabs walk sideways, their excellent vision can see sideways pretty well. Still, they do have trouble seeing behind and below them.
Interesting Facts About Crabs
Crabs are unique creatures, and their adaptations for living on land and in the sea are fascinating. Some crab species have existed for 450 million years, predating the dinosaurs. The horseshoe crab is one crab species known as a living fossil because it’s existed for so long.
Now that we’ve uncovered why crabs walk sideways, there are a few other facts about crabs that you may find interesting.
- 1 million tons of crabs are eaten yearly all over the world
- Female crabs are pregnant for 1-2 weeks
- Pea crabs are the tiniest species of crab in the world. They are so small they live as parasites on other shellfish.
- Crabs are omnivores
- A group of crabs is called a cast
- Crabs keep coral reefs clean by clearing debris and keeping the reefs healthy.
- Crabs communicate by rubbing their claws together
- A crab can regenerate body parts
- If mother crabs are hungry and she has no other source of food, they will eat their babies.
- Crabs have 10 eyes
- A crab’s body is covered in a hard shell called a carapace
- Crabs are pretty bright and have the capacity for complex learning. For example, crabs can learn to move through a maze and remember it up to two weeks later.
- Crabs do not have a heart but have an open circulatory system that pumps blood throughout their body.
- Crabs walk and swim sideways
The reason why crabs walk sideways is due to the joints in their legs. While not all crabs walk sideways, the majority of them do. Crabs also walk sideways due to their shell’s shape, making it difficult to walk in any other direction. Crabs that have more elongated bodies are more likely to walk forwards.