There are thousands of different types of crabs spread out across 4,00 distinct species, but none of them are too picky when it comes to their diet.
More specifically, most crabs are meat-loving hunters and scavengers like fish, crustaceans, shrimp, and other small animals.
Still, they typically eat a variety of foods, including some non-meat options. In other words, some crabs are carnivorous, some are vegetarian, but most species are omnivorous.
Because they don’t see very well, they are not the best hunters in the sea, but they make up for it by eating already dead animals and using their snapping claws to kill smaller animals when the opportunity arises.
Read on to answer the question “what do crabs eat?” and learn more about their diet, food sourcing, hunting methods, and more.
The Crab Diet
- Small fish
- Shrimp, Prawns & Krill
- Dead Animals
- Squid & Whelks
- Small clams & Mussels
- Seaweed & Algae
Crabs typically look for fish on the ocean floor, and for larger crabs, fish can make up around 10% of their diet.
Fish are typically faster and more agile than the slow and steady crab, so most crabs end up eating fish that are already dead or at least injured.
Fish are an excellent energy source of energy while being relatively easy to digest. Eating fish gives crabs protein, essential fatty acids, and fat-soluble vitamins like A, E, D, and K.
Crabs, namely larger crabs like the Blue Crab, Snow Crab, and King Crab, can eat crustaceans like lobsters, crayfish, barnacles, and even other crabs.
Other crustaceans actually make up around 17–18% of the Blue Crab’s and Snow Crab’s diet.
Depending on the specific shellfish, there are various nutritional benefits of crustaceans. But most, especially lobster, will provide crabs with vitamin A, calcium, and iron.
Shrimp, Prawns & Krill
Snow Crabs love shrimp. Shrimps and prawns make up about 17% of a Snow Crab’s diet.
Other crabs like shrimp, too, because shrimp has a lot of protein, does not have a lot of fat, and contains nutritional elements like omega-3s and calcium.
Decaying matter and carrion like dead fish and dead shrimp are important for a crab’s diet.
Because they are not the best hunters given their eyesight and relatively slow pace, they like to scavenge for dead meat as opposed to hunting for living meat sources.
Eating dead animals is an easier way for crabs to get their daily dose of proteins, iron, fat, and vitamins without having to expend energy hunting down live food.
Squid & Whelks
Larger crabs, like Dungeness crabs, are the ones that tend to eat larger animals such as squid and whelks.
But even for a Dungeness Crab, catching and eating a live squid is particularly challenging. That said, they typically only eat squids that are already dead.
Squid and whelks have more protein than other smaller animals, and also a fair amount of iron, calcium, and Vitamin C.
Small Clams & Mussels
King Crabs, which are larger crabs, can ear clams and mussels, and even sea urchins. They prey on these animals using their sense of smell and taste while shifting across the seafloor.
Clams and mussels provide crabs with a healthy dosage of vitamin B12 and omega-3 fatty acids.
Seaweed & Algae
Smaller, sea-dwelling crabs eat both red and green algae, and they look around for opportunities to eat this non-meat diet.
Algae can be found in both saltwater and freshwater environments, providing feeding opportunities for different types of smaller crabs around the world.
Algae is nutritious, helps control a crab’s molting, and helps remove toxins from a crab’s body. And perhaps best of all, from a crab’s perspective, algae cannot run away or fight back.
Crabs may pick up algae with their claws or cut it, scrape it off a rock, or dab at it to get specific pieces.
How Do Crabs Collect Food & Hunt?
Crabs do not have the best eyesight. They also tend to live in murkier, darker areas of the sea where good eyesight would not help them much anyway.
But that doesn’t mean that they cannot hunt at all. When it comes to hunting, crabs rely more on their sense of smell to determine what is close enough to snatch up.
More specifically, the chemoreceptors on their antennae help them sense when chemicals from their prey are released into the water.
Additionally, bigger crabs, like the King Crab, have one big claw they use to crush their prey. When it comes to scavenging, crabs will use their claws—or chelas— to sift through the sand or dirt in search of uneaten bits and decaying morsels.
They also use their claws to pick up the food and put it in their mouths, similar to how humans can use their hands to eat finger food.
How Much Do Crabs Eat?
Crabs eat smaller quantities of food at a time, as they will eat whenever they get those chelas on food, but it’s usually not a large amount of food.
This is why if you are actively trying to feed a crab, they only need to be fed two meals a day to survive.
They also can’t eat a large amount of food, or large bites of food, at once since they don’t have teeth. Their anatomy makes it more difficult to break down food in their mouths, so tearing up their food and eating tinier bites is helpful to crabs.
Most crabs are versatile and not too picky when it comes to eating. Many crabs are omnivorous and opportunistic, essentially eating whatever they can find. Additionally, crabs eat foods high in nutrition and don’t eat large portions at once.
Most of these primary food items for crabs are relevant to water-dwelling crabs, but land-crabs eat other types of foods as well, such as worms and insects.
There are many different options when it comes to a crab’s diet, but ultimately, crabs simply want to eat when they can and not put in too much effort to hunt and kill their food.