Is a Crab a Carnivore or an Omnivore?

By Amy S. Jorgensen

Whether in the wild or in captivity, crabs are omnivores who live off a combination of plant and animal food sources. The omnivorous diet for crabs in the wild still differs greatly from what you might feed your pet hermit, fiddler or red claw crab.

Omnivore Defined

Many animals, including humans, are characterized as omnivores. Unlike herbivores who eat only plant life and carnivores who eat only meat, omnivores regularly consume both types of food giving them a more diverse diet. Types of fish, birds, reptiles and mammals all fall under this category along with crabs.

Wild Crab Diet

In the wild, crabs eat a variety of plants and animals. For example, the blue crab is native to the Atlantic Ocean along the East Coast and eats live plants, snails, fish, crustaceans and other blue crabs. The Alaskan king crab makes its home in the waters around Alaska and Russia where it eat bryozoans and other colony plant life when they are young. Eventually, they begin eating clams, sea urchins, sand dollars, barnacles, mussels, fish and algae. Both the snow crab in Alaska and the Dungeness crab from the Pacific Northwest eat any life forms they can find at the bottom of the sea or ocean, respectively. As these examples illustrate, a variety of crabs in different native environments thrive on diverse diets including both plant and animal life.

Pet Crab Diet

Like wild crabs, most pet crabs also require a diverse diet. Hermit crabs, for example, live off fruit, plants, grasses, decayed wood and any animal protein that happens to come ashore when they are in the wild. Pet hermit crabs need similar diversity. In fact, Petco reports a recent study found that hermit crabs prefer eating different foods at each feeding. These crabs can be given a wide variety of foods, including:

  • Coconuts.
  • Nuts.
  • Nonstarchy vegetables.
  • Raisins.
  • Peanut butter.
  • Cooked eggs.
  • Fresh fish.
  • Cereal.
  • Crackers.
  • Tree bark.
  • Popcorn.
  • Fresh shellfish.
  • Cooked meat.
  • Honey.
  • Mangoes.
  • Papayas.

Hermit crabs also enjoy snacks of frozen plankton, dried seaweed, fruit-based reptile food and drained brine shrimp.

Pet crabs such as the red claw, fiddler and Thai devil crabs also need omnivorous diets in captivity. Care instructions for all of these species specifically recommend they be fed a variety of foods so they receive all of the nutrients they need. In fact, owners who rely primarily on sinking food pellets for their crabs should alternative between those based on algae and those based on protein to ensure the crabs stay healthy. Fiddler crabs, in particular, can eat dried plankton, brine shrimp flakes, as well as pieces of fruit and vegetables.