Every living thing is on one side of the food chain or the other. We eat to live and we live to eat. Crabs are no different from other species. It may look like they’re just floating around on the ocean floor, molting and mating, fighting off invaders and falling in love—but they’re really just trying to live their best life! Interestingly, their food preferences aren’t as simple as you might think, and the other species that like to eat them are very different.
Read on to find out how crabs hunt, how their environment affects the food they eat, and what they like. You might also learn a few shocking facts that you can use at trivia night or to impress your friends.
Crabs are omnivorous scavengers and will eat just about anything they can find. Their diverse diet includes fish, plants mollusks worms, algae, and even other crabs. A crab’s diet depends on its species, habitat, and size. Smaller crabs eat more algae and plant matter, while larger crabs eat more animal prey. But all crabs are opportunistic feeders that will consume a wide variety of foods.
Main Food Sources
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Fish – Both living and dead fish are prime crab prey. They provide protein and omega-3 fatty acids.
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Crustaceans – Crabs eat shrimp, lobster, crayfish, barnacles, and even other crabs for nutrients like vitamin A and calcium.
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Mollusks – Clams, mussels, oysters, squid, and whelks offer iron, vitamin B12, and protein.
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Worms – Marine worms are an easy protein source for crabs to catch and eat.
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Plants – Crabs eat seaweed, algae seagrass and marsh grasses, which provide fiber.
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Carrion – Decaying animals are an easy meal for crabs. Scavenging provides protein without hunting.
Hunting and Foraging
Crabs aren’t active hunters due to their poor eyesight. But they have a strong sense of smell to detect food particles in the water. Their front claws are used to grab crush, and tear prey. Crabs forage for plant matter by scraping algae off rocks with their claws. They use their mouthparts to shred and eat the plants.
Eating Habits
Crabs are constant grazers and opportunistic eaters. They will eat bits of food as they find it rather than consuming large meals. Their small stomachs prevent them from eating a lot at one time. Crabs use their claws as tools to place food in their mouths and tear it into bite-size pieces.
Diet Variations
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Smaller crabs eat more algae, plants, and carrion. Larger crabs eat more fish, shrimp, and mollusks.
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Shore crabs consume more algae and marsh plants while ocean crabs eat animals like fish and worms.
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Some crabs are specialized feeders, like coconut crabs that consume coconuts.
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Plankton-eating crabs sieve tiny organisms from the water.
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Carnivorous crabs like spider crabs subsist mostly on snails, clams, and other crabs.
Unique Digestion
Crabs digest their food in a two-part stomach. The cardiac stomach filters and shreds food while the pyloric stomach absorbs nutrients. Food is stored, sorted, and ground up before moving through the digestive system. Crabs expel indigestible particles from their mouths as food pellets.
So while crabs aren’t picky eaters, their diverse diet provides optimal nutrition. Their claws allow crabs to be mobile scavengers and eat a little bit of everything the ocean has to offer, from algae to fish. This gives crabs the balanced diet they need to thrive in their coastal habitats.
To Hunt or Be Hunted
Did you know that crabs smell from their antennae?! Crabs have chemoreceptors located within their antennae that allow them to detect chemicals in the water that are released by their prey. These chemoreceptors also help in determining what prey is worth eating and what they should be attracted to or deterred by. Furthermore, crabs have separate antenna-like appendages close to the antennae that help them to sense their surrounding environment.
Crabs are great hunters because they can taste and smell very well. These senses also help them get away quickly from animals that are trying to eat them.
When crabs get close to their favorite food, they can “taste” it using hairs on their pincers, feet, and mouth parts.
What kind of animals should crabs watch out for to stay on top of the food chain?
Like most small living things, crabs have multiple predators that they must keep on their radar throughout the day. Taking the Dungeness crab for example, their natural predators include halibut, dogfish, sculpins, octopus, sea otters, and even other species of crab. Salmon also feed on crab larvae.
What species hunt crabs depend on their environment.
According to the Alaska Department of Fish and Game,
“People, sea otters, octopuses, and Pacific halibut are some of the species that eat hard-shelled Dungeness crabs. In some areas, larger Dungeness crabs and staghorn sculpin are important predators of juvenile Dungeness crabs.” In the soft-shell state, they are preyed upon by many additional species. ”.
And in comparison, looking at the Blue crab, found near the Chesapeake Bay:
“Predators include large fish like croakers and red drum; fish-eating birds like great blue herons; and sea turtles.”
What do crabs eat?
FAQ
What food does crab eat?
What do crabs eat on land?
What can crabs not eat?
What feeding type is a crab?
What do crabs eat in the ocean?
In the ocean, crabs have access to a wide variety of food sources. They will typically eat algae, plankton, mollusks, and small fish. Some species of crab even have a symbiotic relationship with certain types of algae; the crab will eat the algae and then excrete it back into the water, providing nutrients for the algae to grow.
What do blue crabs eat?
They typically forage for aquatic plants such as algae, seaweed, and macroalgae, as well as small invertebrates like worms, mollusks, crustaceans and even fish eggs when available. Like other species of crabs, blue crabs are also known to hunt for larger prey like clams and small fishes when they can.
Are crabs omnivores?
Crabs are generally omnivores, feeding on a mix of algae, plants, mollusks, small fish, and detritus, though some species have more specialized diets. How long do crabs live? The lifespan of crabs varies widely among species, ranging from 3 to 30 years. Can crabs swim?
What do crabs eat in a coral reef?
Crabs that live in the coral reef will typically eat algae, plankton, small fish, and invertebrates. Some species of crab even have a symbiotic relationship with certain types of algae; the crab will eat the algae and then excrete it back into the water, providing nutrients for the algae to grow. What do crabs eat in captivity?