Crabs are crustaceans found across diverse environments, including oceans and land. They are opportunistic, with varied diets and feeding strategies adapted to their habitats.
General Crab Diet
Most crabs are omnivores and scavengers, consuming both plant and animal matter. They play a role in ecosystems as detritivores, breaking down decaying organic matter and recycling nutrients. Crabs commonly feed on a variety of items, including algae, detritus, small invertebrates like worms and mollusks, small fish, and carrion.
Diverse Diets by Crab Type
Crab diets vary significantly depending on the species and their specific environment. Fiddler crabs, for instance, are primarily detritivores, sifting through mud and sand to filter out organic matter such as algae, bacteria, and fungi. They use their smaller claw to scoop sediment into their mouths, extracting food particles.
Hermit crabs are omnivorous scavengers, consuming detritus, algae, and small dead organisms. They also eat various fruits and vegetables when available.
Blue crabs are active predators and scavengers, known for eating small fish, shellfish like clams and oysters, worms, and plant material. They will even consume smaller or soft-shelled blue crabs.
Land crabs, such as coconut crabs, have a more terrestrial diet. Their food sources include fruits, nuts, seeds, and carrion.
How Crabs Find and Consume Food
Crabs find and consume food using senses and specialized body parts. They rely on chemoreceptors, sensory hairs on antennae and legs, to detect chemicals from potential food sources. These receptors allow them to “smell” and “taste” their surroundings, even in dark or murky conditions.
Their claws, or chelipeds, are used for manipulating food. Crabs use them for grasping, tearing, crushing, and delicate manipulation.
Many species possess two different types of claws: a larger, stronger crushing claw and a smaller, more nimble feeding claw used for shoveling food into their mouths.
Mouthparts such as mandibles, maxillae, and maxillipeds further process food, filtering, sorting, and moving it into the mouth. Some species, like fiddler crabs, also employ filter feeding, using their mouthparts to strain food particles from water or sediment.
What Crabs Should Not Eat
Certain substances are harmful to crabs, particularly in captivity. Processed human foods, including those high in salt, sugar, preservatives, or artificial ingredients, can be toxic and should be avoided. Crabs, especially hermit crabs, are unable to properly digest dairy products due to a lack of necessary enzymes.
Unknown plant matter should not be fed to crabs, as some plants can be poisonous. Cooked or seasoned foods are also unsuitable because they lack natural nutrients and may contain harmful additives like excess salt or spices. Foods containing ethoxyquin, a pesticide sometimes found in commercial crab or fish foods, are highly poisonous.