What Do Crabs Eat?


Found in habitats ranging from ocean depths to rainforest floors, crabs have developed an astounding diversity of feeding strategies that allow them to thrive in almost every corner of the planet. With more than 6,700 species, these resilient crustaceans exhibit an outstanding capacity to locate and consume food in diverse ways. Understanding these feeding habits is essential for both recognizing their ecological importance and providing proper care in captivity
The following AnimalWised article explores the diverse diets of crabs, both in the wild and as pets, with examples of feeding habits across various species.
What do crabs eat in the wild?
Crabs belong to the order Decapoda, with over 6,700 known species found across the world. These hardy crustaceans have evolved to thrive in nearly every aquatic environment, from the deepest ocean trenches to mountain streams, and some even spend most of their lives on land.
You'll find crabs in three main environments:
- Marine waters: from polar regions to tropical seas.
- Freshwater systems:rivers, lakes, and streams.
- Terrestrial habitats: coastal areas and tropical forests.
Most crabs are omnivores, meaning they eat both plants and animals. Each species has adapted its feeding habits to its specific environment, from deep oceans to coastal areas and even on land.
Ocean crabs like the Blue crab (Callinectes sapidus) and the European green crab (Carcinus maenas) actively hunt small fish, mollusks, and other crustaceans. They also feed on algae, seaweed, and plankton.
The Giant Japanese spider crab (Macrocheira kaempferi) scavenges on the ocean floor, eating both dead and living organisms it finds in the deep waters.
Freshwater crabs (Potamidae family) live in rivers and lakes where they eat aquatic plants, insects, worms, and decaying organic matter. The red claw crab (Perisesarma bidens) particularly enjoys eating water plants and biofilm that grows on rocks and wood.
Land crabs, such as the famous Christmas Island red crab (Gecarcoidea natalis), have evolved to be primarily herbivorous. They feed on fallen leaves, fruits, flowers, and seedlings. However, they'll also eat dead animals and smaller invertebrates when available.
Did you know female crabs can carry up to 2 million eggs at once? Learn more amazing facts about crab reproduction in our other article.

How do crabs gather food?
Crabs use their claws as tools to get food. They crush shells, tear plants, and grab moving prey. Many species dig through sand or mud to find hidden food. This hunting process changes with the tides - some crabs search for food when the tide is low and the seafloor is exposed, while others wait for high tide to reach new feeding areas.
Some crabs have developed special ways to eat. Filter-feeding crabs strain tiny food particles from the water using parts of their mouth designed just for this purpose. This shows how crabs have evolved to get food in many different ways.
In their ecosystems, crabs work as both hunters and cleanup crew. They eat live prey and break down dead material, which helps keep their habitats healthy. You can find crabs eating in almost every type of water environment, from deep oceans to shallow streams.
Each crab species has found its own way to get food, which explains why these animals thrive in so many different places around the world.
From their powerful claws to complex digestive systems, every part of a crab's body is perfectly designed for finding and processing food. Learn more about these amazing adaptations in our crab anatomy article.

What do crabs eat in captivity?
Keeping crabs as pets requires understanding their dietary needs, which differ by species. Whether you have a hermit crab (Paguroidea), fiddler crab (Uca pugilator), or red claw crab (Perisesarma bidens), providing a balanced diet is key to their health in captivity.
Pet crabs need a mix of protein, vegetables, and minerals. For protein, you can offer small pieces of fish, shrimp, bloodworms, or commercial fish flakes. Many species enjoy fresh vegetables like carrots, sweet potatoes, and leafy greens. Fruits such as apples, mangoes, and coconut provide important nutrients, but serve these in moderation due to their sugar content.
Calcium plays a vital role in shell development and molting. You can provide this through cuttlebone, crushed oyster shells, or commercial calcium supplements. Some species such as the red claw crab (Perisesarma bidens), for example, also need access to both fresh and salt water because the salt contains trace minerals essential for their health. Did you know that a crab's hard shell serves as more than just armor? Discover how their unique body structure enables their survival in our other article.
How to feed your pet crab:
Feed your crabs small portions once or twice daily, removing uneaten food after a few hours to prevent water contamination. Most pet crabs eat actively at night, so evening feeding often works best.
Watch your crab's eating habits. They often eat more before and after molting. During molting, they might not eat for several days, which is normal. Keep fresh water available at all times, and ensure food pieces are small enough for your crab to handle with its claws.
For optimal health, rotate food types throughout the week. This mimics the varied diet they would find in nature and ensures they get all necessary nutrients.

Diet of different crab species
As mentioned before, each crab species has evolved specific dietary preferences shaped by its habitat and physical capabilities. Let's explore how different crab species have adapted their diets to their environments.
What do blue crabs eat?
Blue crabs (Callinectes sapidus) are aggressive predators found along the Atlantic coast. They use their powerful front claws to crack open clams, mussels, and oysters. These crabs also hunt small fish, snails, and even younger blue crabs.
During winter months, they supplement their diet with seaweed and underwater plants. Their strong shells and quick movements make them effective hunters in both shallow and deeper waters.
What do hermit crabs eat?
Hermit crabs (Paguroidea) show an impressive dietary flexibility. In the wild, they eat a mix of plant and animal matter.
The Caribbean hermit crab (Coenobita clypeatus), a popular pet species, naturally feeds on fallen fruit, leaf litter, and occasional carrion. Their smaller claws are perfect for picking up tiny food particles and filtering organic matter from sand. They also scavenge along the shoreline, finding meals in what the tide brings in.
What do coconut crabs eat?
The coconut crab (Birgus latro), the largest terrestrial arthropod, has unique eating habits. Despite their name, coconuts make up only part of their diet. These powerful crabs can crack open coconuts with their massive claws, but they also eat fruits, nuts, and carrion.
On islands where they live, they'll climb trees to harvest pandanus fruits and other tropical plants. They have even been observed hunting seabirds, showcasing their opportunistic nature. Did you know these impressive crustaceans can climb palm trees and inhabit some of the world's most remote islands? Explore where do coconut crabs live in our other article.
What do spider crabs eat?
Spider crabs (Majoidea family), including the Japanese spider crab (Macrocheira kaempferi), are primarily deep-water scavengers. Their long legs allow them to cover large areas of the seafloor where they feed on dead fish, mollusks, and sea urchins. Many species also graze on algae and collect detritus. Some smaller spider crabs camouflage themselves with seaweed, which they may eat when other food is scarce.

If you want to read similar articles to What Do Crabs Eat?, we recommend you visit our Healthy diets category.
- Hickman, CP et al (2009). Comprehensive Principles of Zoology . McGraw-Hill, Madrid.
- Falciai, L. & Minervini, R. (1995): Guide to the decapod crustaceans of Europe . Omega.
- Martin, JW & Davis, GE (2001): An updated classification of the recent Crustacea . Natural History Museum of Los Angeles County. Science series 39.
- Moreno-Casasola P. (Ed.) 2006. Veracruz environments: the coast of La Mancha . Mexico, 576 pp. Capistrán, A., Utrera, M.E.
- Wolfrath, B. (1992). Field experiments on feeding of European fiddler crab Uca tangeri . Marine Ecology Progress Series 90: 39-43.
- Dahdouh-Guebas, F. et al. (1997). Food preferences of Neosarmatium meinerti de Man (Decapoda: Sesarminae) and its possible effect on the regeneration of mangroves . Hydrobiology 347, 83–89.
- Etchian, OA et al (2016). Some ecological aspects of the gecarcinid land crab, Cardisoma armatum Herklots, 1851 (Crustacea, Brachyura, Gecarcinidae) from the estuarine region of the Comoe River, Côte d'Ivoire . Int J Biol Chem Sci 10(2): 457-474.
- Chia, OKS & Ng, PKL (2006) T he freshwater crabs of Sulawesi, with descriptions of two genera and four new species (Crustacea: Decapoda: Brachyura: Parathelphusidae) . The Raffles Bulletin of Zoology 54 (2): 381-428.