Crabs have a hard shell that protects them from predators. But, some animals still like to include some crab in their diet. So, what are a crab’s predators?
Different crab species have other predators. Most crabs are eaten by sharks, fish, birds, sea turtles, and humans. Crabs can be cannibalistic and eat their children if there is not enough food. Birds and other smaller ocean animals will eat any crab larvae they can find.
You may have noticed we mentioned that crabs eat their own young. If you would like to learn more about why they do this, keep on reading.
This guide goes over all the necessary information about a crab’s predators. We will look at why they eat them and how.
Let’s dive in.
What are a crab’s predators?
Common crab predators include fish, birds, turtles, and humans. There are 6,500 crab species that we know of, and they all have a range of different predators.
What animal eats these crabs is based on where the crab lives. Availability is a critical factor in determining whether a predator will prey on a crab.
Crabs are also slow-moving animals, which makes them an easy target for predators. Predators use different tactics to sneak up on a crab so it can’t hide.
These predators will eat crabs for many different reasons. Crabs can provide many proteins and vitamins.
Let’s go into more detail about these predators.
There are many species of fish that eat crab, including larger fish species. These fish include sharks, bass, dogfish, cobia, and jellyfish.
Smaller fish also have some crab in their diets but eat juvenile crabs and larvae instead of adults. This can also include eels and sea rays.
Crabs are more vulnerable when they are molting. This is when the crabs shed their outer shells to allow them to grow.
Since they don’t have their hard shells to protect them, predators can take advantage of this period. It also makes the crab much easier to eat as the predator won’t need to break the shell.
Fish prefer blue crabs in their diets, as many are available in their habitats. They are slow moving which is great for fish looking for a quick meal.
Large fish like sharks can eat the shell of a crab as they have strong, powerful jaws. Other big fish rip the flesh from inside the crab’s shell.
They often do this with many types of crab species. This includes mud crabs, hermit crabs, spiny lobster, and king crabs.
Small fish prefer to feed on larvae that they find hidden in small crevices or in reefs. They also eat juvenile crabs during molting season.
2. Sea turtles
Sea turtles enjoy many crustaceans in their diets, including crabs. The main sea turtle species that eat crabs are Kemp’s ridley and loggerhead sea turtles.
The loggerhead sea turtle has special adaptions that allow them to eat crabs. Their powerful, serrated jaws allow them to crush up the shells of their prey and eat the flesh.
As their diets change when they age, hatchlings don’t eat crabs. They can’t hunt them as they are too small and aren’t big enough.
Only adult sea turtles eat crabs, as their jaws have fully developed. This is important as they need strong jaws to crush the crab’s hard shell.
Not all sea turtles eat crabs, like the green sea turtle. Green sea turtles prefer to eat plants like algae and seaweed.
Crabs can also eat sea turtles and their eggs as well. Ghost crabs often prey on sea turtle hatchlings after hatching on the beaches.
This is called mutual predation and is very rare. Ghost crabs will dig up hatchling eggs and will also hunt hatchlings attempting to make it to the sea.
Sea turtles aren’t the only reptiles that eat crabs. Many snakes, crocodiles, tortoises, land turtles, and lizards eat them too.
Sea birds are also one of the many predators of crabs. Birds like egrets, diving ducks, and herons target crabs and include them in their diets.
They often like to feast on blue crabs. This is because these crabs live in coastal and tidal waters where these birds can pick them up.
Coastal birds don’t only prey on fully grown crabs. They also eat larvae they find offshore and young crabs on the shore.
Their beaks help them to have a good grip on the shell once they pick it up. They then proceed to drop the crab from a high distance to smash the crab’s protective shell.
Once the shell is cracked open, the bird can eat the inner meat. But, not all sea birds use this method of hunting crabs.
Herons have a different way of eating these crustaceans. They have strong, sharp beaks that they use to stab crabs in shallow waters.
They then crunch up the crab’s shell as they have strong specialized beaks. After the shell is smashed, they can swallow it whole for the meat.
Gulls also eat crabs that have washed up on the shore. They flip over the crab to avoid its claws, then break its shell open and eat the meat.
A variety of different mammals feed on crabs. This includes:
- Sea otters
- Sea lions
Sea otters are notorious for enjoying some crabs in their diet. Sea otters have many different methods of hunting they use to prey on crabs.
They will dive to the bottom of the sea floor to grab the crabs and bring them up to the surface. They will then use their paws to break up the shells and access the meat.
Sea otters can also visit rocky reefs and take a big rock. They will put the rock on their stomach and use it to smash open the prey’s shell for the meat.
Crabs are the main part of a sea otter’s diet. They can eat around 30 percent of their body weight and go through a lot in one day.
Some species of sea otter specialize in eating crab. This includes the Asian small-clawed sea otter and the cape clawless sea otters.
Dolphins, porpoises, and whales will also prey on crabs. They can use their strong jaws to open the crab’s shell and eat the meat.
Seals also will include crabs in their diets. The crabeater seal is named after their diets since they love to eat crabs but prefer to eat krill.
It is a known fact that humans eat crabs. They are a popular food served worldwide and are important in many cultures.
You may have tried crab meat in the form of crab legs or crab cakes. Crab meat is described as being sweeter than lobster and flakier in texture.
Crabs can provide humans with many sources of nutrients. This includes omega-3, fatty acids, and selenium.
Evidence suggests that crabs were eaten in Maryland in the 1200s. But the earliest humans were found to have eaten crabs on the beaches of East Africa.
Humans have eaten crabs for centuries, but recent demand for them has led to many species becoming over-exploited. Many fisheries have been affecting crab populations for many years.
The oldest crab species, the horseshoe crab, is listed as vulnerable. This is because of overharvesting, habitat loss, and being used in biomedical testing.
Mud crabs in Madagascar are also in danger of becoming threatened because of overexploitation. They have also lost 136 thousand acres of habitat as of 2020.
Another overexploited species include blue crabs. Between the late 1990s and early 2000s, there were reports of overexploitation in Maryland.
The equipment used can also be dangerous and contribute to ocean pollution. Heavy machinery is used and can be a hazardous job to complete.
Left behind equipment called ghost gear also affects other populations. For example, sea turtles can get caught in traps which causes them to become endangered.
6. Other crabs
We mentioned this at the beginning of the article, which may have interested you. Crabs are known to be cannibalistic and will eat each other if necessary.
It is not common, but it does happen. Mothers will eat their own young when there is a shortage of food, but this is rare.
Smaller crabs are also targeted by bigger crabs that cannot find another food source. They will use their claws to crush the small crab’s shell and then eat them.
Blue crabs are more guilty of this than any other species. They pick on weaker crabs with missing limbs, parasites, or bad health.
Larger crabs often have no preference when scavenging the ocean floor. This means they may come across smaller crabs and feast on them.
A crab’s predators include birds, mammals, humans, turtles and fish. Crabs will also eat their young as well.
Different predators have ways of eating the crabs. Often, they will smash open the shell and eat the meat.