How Does a Crab Eat?

Crabs may be a favorite food for some people, but they need to eat too. They often live in dark or muddy areas, where it can be difficult to find prey by eyesight. So how do crabs find food, and how do they eat? And, interestingly, what types of food do they like to eat?

How Crabs Find Food

Like many other marine animals, crabs rely on their sense of smell to find prey. Crabs have chemoreceptors that allow them to detect chemicals in the water that are released by their prey. These chemoreceptors are located on a crab's antennae. These are long, segmented appendages near the crab's eyes that have both chemoreceptors and allow them to feel its surroundings.

Crabs also have antennules, shorter antenna-like appendages near the antennas that allow them to sense their environment. A crab can "taste" using hairs on its mouthparts, pincers and even its feet.

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Senses of Taste and Smell

Crabs have pretty well-developed senses of taste and smell. Fishing for crabs, or crabbing, using pots and cages relies on these senses, and makes it possible to catch crabs. The pots are baited with a variety of smelly things, depending on the target crab species. Bait can include chicken necks, pieces of fish such as eel, menhaden, squid, herring and mackerel.

As the bait hangs in the trap in a bag or in a bait jar, odorous chemicals waft out into the ocean, attracting hungry crabs. Depending on water flow, these conditions can affect their senses to detect prey.

What and How Crabs Eat

Crabs aren't picky eaters. They will eat everything from dead and living fish to barnacles, plants, snails, shrimp, worms and even other crabs. They use their claws to grab food particles and put the food into their mouths. This is similar to the way humans eat using their hands or utensils.

Crabs also use their claws to manipulate or break up the food so they can place it into their mouths more easily in smaller bites. When crabs have to break through shells of other sea life, their strong claws come in especially handy while their other appendages help them quickly move to catch various types of prey.

Different Crabs, Different Diets

Different crabs like to eat different types of sea life and plants. Dungeness crabs, for example, may snack on squid and worms, while king crabs like to nosh on clams, mussels, worms and sea urchins. Basically, king crabs hunt for prey on the ocean floor and often eat decaying animal matter as well as live sea life.

Sources and Further Reading

• “Frequently Asked Questions.” Blue Crab.
• “Encyclopedia of Tidepools and Rocky Shores.” Edited by Mark W. Denny and Steve Gaines, University of California Press, 2017.
• “Dungeness Crab." Oregon Agriculture in the Classroom.
• .Blue Crab Anatomy web.vims.edu.