American Oceans

Are Horseshoe Crabs Dangerous?

Horseshoe crabs are among the weirdest-looking creatures that have ever existed. With their armored shell and spiky tail, these crabs look menacing. But are horseshoe crabs dangerous?

a dangerous looking horseshoe crab with spikes and pointy tail

In short, horseshoe crabs aren’t dangerous to people. The only thing people should be scared of is accidentally stepping on one. The only way one of these crabs can hurt you is if you happen to step on one!

Horseshoe Crab Anatomy

Horseshoe crabs are a species of marine arthropods that are more closely related to spiders and scorpions than crabs. Females are generally larger than males at 18 and 14 inches long, respectively. 

horseshoe crab body overview showing its anatomy

Horseshoe crabs have three sections—the prosoma, the opisthosoma, and the telson. The prosoma is the head, and it has a spiked shell covering it. The opisthosoma is the crab’s abdomen. The shell also protects the opisthosoma.

The telson is the crab’s tail. The tail is four to six inches long, on average. Some people become frightened by the horseshoe crab’s tail, which looks like it could be venomous, like a stingray. 

Luckily for us, that’s not the case. Horseshoe crabs use their tails to flip themselves over if they end up on their backs and steer while in water.

horseshoe crab tail to flip body shell

The spikes on the horseshoe crab’s shell are also not dangerous, although they can hurt. The spikes help protect the horseshoe crab from predators because they make the crab look less appetizing.

Like most crabs, horseshoe crabs have pincers and a mouth, but neither can hurt humans. The horseshoe crab’s pincers are their first set of legs, and they’re much smaller than other crabs. 

Although horseshoe crabs have pincers, they’re much too small to do any damage to people.

horseshoe crab pincer close shot

Their pincers are generally only 1 inch long and don’t have enough force to cause people any damage.

Do Horseshoe Crabs Attack Humans?

No, horseshoe crabs will not attack humans. In most cases, a horseshoe crab will avoid the noise and commotion caused by human activity. They won’t seek out humans and attack them.

person holding a horseshoe crab on beach

Even when people and horseshoe crabs are in close proximity, horseshoe crabs won’t attack humans. 

Horseshoe crabs eat almost anything they can fit into their mouths, which is very small. Horseshoe crabs generally eat worms, clams, small crustaceans, other small animals, and even algae. The one thing they won’t eat is large animals. 

One of the reasons they don’t eat large animals is because they don’t have teeth in their mouths.

horseshoe crab finding food to eat

Instead, they crush food between their pincers before eating it. Considering how small these creatures are, they won’t be doing that to a person anytime soon!

Can Horseshoe Crabs Kill Humans?

Although this may seem absurd, it’s common to think that horseshoe crabs are so dangerous, they could kill a person. Most of this has to do with the similarities between their tail and the tail of a stingray.

spiked shell and tail of a horseshoe crab

But there’s no reason to think a horseshoe crab could kill a person. Their tails don’t contain any harmful toxins, and neither do their shell spikes.

Since their defenses aren’t toxic, there’s no reason you should be afraid that a horseshoe crab can kill you.

What to Do if You See a Horseshoe Crab

The most common horseshoe crab in the United States is the Atlantic horseshoe crab. It lives in the Atlantic Ocean, from Maine to the Gulf of Mexico.

close up shot of horseshoe crab

Horseshoe crabs mainly live in coastal areas, such as lagoons and estuaries, but they can also swim considerable distances and depths.

If you happen to come across a horseshoe crab while out at the beach, examine its activity. If it’s crawling around on its stomach like normal, leave the crab alone. It’s going about its life, and you should leave it in peace.

If you come across a horseshoe crab that’s lying on its side or back, you can step in to help. Sometimes these creatures will accidentally flip over, and it can be difficult for them to right themselves.

flipped horseshoe crab on the beach

To help a flipped horseshoe crab, grab the crab by the side of the shell along the opisthosoma or abdomen.

By picking the crab up by the side, you’ll avoid the spikes on its shell. Then, gently place the crab right-side-up on the ground so it can get back to its habitat.

Are Humans Dangerous to Horseshoe Crabs?

Although some people have the misconception that horseshoe crabs can hurt people, it’s much more likely that a human will hurt a horseshoe crab.

humans catch horseshoe crabs on the beach

Atlantic horseshoe crabs are considered a vulnerable species, meaning they are close to becoming endangered.

Habitat loss is one of the many dangers humans pose to horseshoe crabs. Since horseshoe crabs primarily reside in shallow water, they are constantly in contact with humans. One concern of many is the use of dredging which could disrupt a horseshoe crab’s habitat. 

As humans encroach on their habitat, horseshoe crabs lose valuable resources, like food and shelter.

horseshoe crab going to its natural habitat

When they lose these resources, horseshoe crabs must either leave the area or find new resources, making their life much harder.

Humans also harvest horseshoe crabs, but not for food. The pharmaceutical industry uses horseshoe crab blood to make substances used for bacterial toxin testing.

Pharmaceutical companies take about a third of the crab’s blood and then release the crab back into the ocean.

pharmaceutical companies takes third of horseshoe crabs blood

Although pharmaceutical companies claim that this method is safe, many of the crabs they release back into the wild die quickly after.

This may be due to weakness after blood draws or because they lost too much blood. In either case, this is another way humans are dangerous for horseshoe crabs.

Final Thoughts

So, are horseshoe crabs dangerous? Horseshoe crabs aren’t dangerous to humans in almost any regard.

The only thing you need to be aware of is the spikes on their shells. As long as you’re careful, you won’t have any chance of touching their spikes.

Humans pose a much greater threat to horseshoe crabs than they do to us. So, next time you’re at the beach, and you see a horseshoe crab, leave it alone unless you see it struggling!

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