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 found all over the world, inhabiting oceans, seas, and freshwater habitats With over 4,000 species of crab, their diets are as diverse as the environments they live in But when it comes to ocean-dwelling crabs, what exactly do they eat down there in the deep blue sea? Let’s find out!
An Omnivorous Nature
Most crabs are omnivorous, meaning they eat both plant and animal matter. Their diverse diet allows them to adapt to different food sources based on availability. Crabs are not picky eaters and will consume almost anything they can get their claws on This includes both live prey and scavenging decaying animals that have perished
Their primary food sources are
- Small fish
- Crustaceans
- Worms
- Mollusks
- Algae
- Plants
- Carrion
Larger crabs may also eat smaller crabs in a practice known as cannibalism. The crab’s hardy nature and willingness to eat most anything aid in its survival across various ocean habitats.
Hunting Methods
Crabs are outfitted with several tools to help them catch and consume food:
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Claws – Crabs use their characteristic pincers to grasp, tear apart, and shovel food into their mouths. Their claws allow them to capture and break down prey.
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Mouthparts – Specialized mouthparts sort, shred, and digest food. Some crabs even have tooth-like structures in their stomachs to grind up food.
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Walking Legs – Sensors on their legs help crabs locate and taste potential food sources.
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Antennae – Contain chemoreceptors that detect chemicals released by prey. This allows crabs to hone in on food nearby.
While not the fastest or most agile hunters, crabs use their senses and tools to catch live animals and scavenge whatever becomes available. Their adaptable nature makes them effective feeders in the ocean environment.
Diverse Food Sources
The ocean offers crabs a wide buffet of food choices. Here are some of their favorite ocean edibles:
Fish
Crabs feed on all varieties of fish they encounter. Fish make up about 10% of some crab species’ diets. Crabs may eat deceased fish or living ones if small and slow enough to capture. Fish provide crabs with protein, healthy fats, and vitamins.
Crustaceans
Crabs eat other crustaceans like shrimp, lobster, and even their own kind. Shrimp can comprise up to 17% of some crabs’ intake. Crustaceans supply crabs with protein, calcium, and other nutrients. Larger crabs have an easier time breaking through crustacean shells with their crushing claws.
Mollusks
Mollusks like clams, mussels, whelks, and squid are part of many crabs’ diets. Some have enough strength in their claws to pry open tightly shut bivalves. Mollusks provide vitamins, minerals, omega-3s and other health benefits.
Plants
Crabs consume a variety of plants including seaweed, seagrass, algae, and aquatic vegetation. Smaller crabs often graze on vegetation growing on reefs or the seafloor. Algae helps regulate molting, removes toxins, and provides nutrition. Plants offer variety and are easy for crabs to access.
Carrion
Crabs scavenge on deceased animals that sink to the seafloor. It’s an easy meal that provides sustenance without hunting efforts. Rotting carcasses supply protein, fat, and nutrients to crabs able to utilize them. Their hardy digestive systems allow them to extract value from decaying matter other animals couldn’t consume.
Ideal Foraging Ground
The ocean floor offers an abundance of food if you know how to locate it. Crabs sift through sand and mud feeling for food sources. Their senses guide them toward anything digestible. Tidal currents also carry nutrients into their habitats. With an omnivorous palate and the ocean’s diversity, crabs seldom go hungry.
Next time you crack open a shelled delicacy, think about the feeding behaviors that nourished your meal throughout its ocean-dwelling life. The ocean ecosystem supports a complex food web, with crabs filling a vital role as generalist feeders. Their flexible diets and adaptive hunting allow crabs to thrive across diverse marine environments.
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.”
The incredible unity of the spider crab | Spy in the Ocean – BBC
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.
Do crabs eat fish?
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.
What do Snow crabs eat?
Snow crabs: They feed on clams, snails, and small fish. Hermit crabs: They typically eat algae and seaweed. Some species will also eat carrion and dead animals. Coconut crabs: Their diet includes fruits, nuts, and smaller animals such as insects and crabs.
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?