Crabs are consumed by a variety of animals in coastal and marine ecosystems. If you want a quick answer, some of the top animals that eat crabs include octopuses, fish, birds, raccoons, sea otters, and even other crabs.
In this article, we’ll take a closer look at crab predators and what types of crabs they like to eat.
Birds That Feed on Crabs
Seagulls
Seagulls are opportunistic birds often found around coastal areas. They have adapted to take advantage of food sources provided by humans, but also forage in their natural habitat. Seagulls frequently feed on small crabs like fiddler crabs and mole crabs found along sandy beaches during low tide.
Their sharp beaks allow them to crack through the hard shells of crabs to get to the meat inside.
Research indicates that around 25% of seagulls’ diet consists of crustaceans like crabs. A 2021 study found that seagull colonies located near estuaries rich in crab had better breeding success compared to colonies farther away [1].
So crabs provide an important supplementary food source for sustaining seagull populations.
Herons
Herons are adept hunters that patiently stalk the shallow edges of saltwater marshes and mangroves looking for prey. When the tide goes out, shore crabs emerge from their hiding spots among the grass beds to scavenge the exposed mudflats.
Herons take advantage with their sharp vision and quick reflexes to snatch up crabs in their dagger-like bills.
Great blue herons and great egrets in particular can swallow small crab whole. Larger crab species get bashed against a rock or tree branch held tightly in the heron’s foot to break the shell before consumption.
Researchers have identified crab parts and shells as a frequent component of heron stomach contents and regurgitated pellets [2]. So crab predation clearly helps sustain heron populations residing near the coast.
Egrets
Like herons, egrets stalk saltwater flats when the tide recedes to hunt for crabs. Their elegant plumes are a common sight along North American coastlines from Canada down to the Gulf of Mexico. Snowy egrets and reddish egrets are two crab-eating species.
One field study in Texas found that crabs, including fiddler crabs, blue crabs and marsh crabs, accounted for 19% of the diet of snowy egrets living in a coastal salt marsh. Reddish egrets ate even more crabs, which represented 42% of their total food intake tracked over a year.
Egrets populations have rebounded after near extinction in the late 19th century due to hunting for their decorative feathers. Protecting crab habitat in coastal wetlands remains vital for maintaining healthy egret numbers going forward.
Mammals That Prey on Crabs
Raccoons
Raccoons are opportunistic omnivores that will eat just about anything they can get their adorable little paws on, including crabs. These bandit-masked mammals are very dexterous and use their front paws to feel around in the sand for buried crabs.
Once they’ve located their crustacean prey, raccoons use their nimble fingers to quickly snatch up the crab before it can pinch them with its claws. Raccoons have even been known to wash their food in water, dunking crabs in tidepools before consuming them.
While not their primary food source, crabs make up a decent portion of the raccoon diet, especially in coastal areas. In fact, analysis of raccoon scat samples taken along the Virginia coastline showed that nearly 20% of their diet was made up of crabs.
So next time you’re at the beach, watch out for sneaky raccoons prowling the shoreline looking to grab an unsuspecting crab snack.
Sea Otters
With their unrivaled ability to use rocks as tools to crack open hard-shelled prey, sea otters are masters at consuming crabs. These marine mammals are common crab predators, feeding on a variety of species including Dungeness crabs, rock crabs, and king crabs.
Sea otters will dive down to the ocean floor, pry a crab off the seabed, then float on their backs at the water’s surface to eat their catch. Using their chests as tables, sea otters will crack open the hard shell of a crab with a stone and extract the tasty meat inside.
Research indicates nearly 40% of a sea otter’s diet is made up of crabs and other crustaceans. Their crab predation helps regulate crab populations and maintain balance in the kelp forest ecosystem. So while they may be cute and cuddly-looking, sea otters are also ruthless hunters when it comes to devouring crabs!
Seals
Seals are excellent swimmers and use their speed and agility in the water to hunt down swift-moving crabs. Species like harbor seals and gray seals feed on a variety of crab species including blue crabs, rock crabs, Jonah crabs, and spider crabs.
Using their whiskers to detect the faint currents made by crabs moving along the seafloor, seals can pinpoint the location of their shelled prey. A study of harbor seals in Estuary England showed that crabs accounted for nearly 15% of their total diet.
Seals will often toss crabs around to remove the limbs before crunching through the hard shell and savoring the meat inside. While fish make up a larger portion of their diet, seals do supplement their nutritional intake with a steady supply of crabs.
Their ability to hunt these elusive crustaceans demonstrates the remarkable predatory skills of seals.
Reptiles and Amphibians Eating Crabs
Sea Turtles
Sea turtles are large air-breathing reptiles that inhabit tropical and subtropical seas across the world. Many species of sea turtles, such as green sea turtles and loggerhead sea turtles, are opportunistic omnivores that will eat crabs as part of their varied diet.
Crabs make up an important protein source for sea turtles.
Sea turtles use their strong jaws to crush the hard shells of crabs before swallowing them whole. Some favored crab prey for sea turtles includes blue crabs, mole crabs, and hermit crabs. While adult sea turtles are too large to be threatened by crabs, young juvenile turtles are vulnerable to being eaten by large crabs species in their ocean habitats.
Alligators and Crocodiles
Alligators and crocodiles are large reptilian apex predators that inhabit freshwater habitats such as rivers, lakes, and marshes. Both alligators and crocodiles are opportunistic hunters and will readily eat crabs that live in their aquatic domains.
Crabs are easy prey for these mighty reptiles. Alligators and crocodiles use their immensely powerful bite force to easily crush crab shells with their jaws. They swallow crabs whole. Favored crab prey includes river crabs, swamp crabs, and fiddler crabs that dwell alongside alligators and crocodiles.
Alligators and crocodiles play an important role as crab predators in freshwater ecosystems. They help keep crab populations in balance. On occasion, crocodilians have even been observed leaping out of the water to snatch unwary terrestrial crabs on river banks!
Fish and Other Aquatic Animals
Groupers
Groupers are large predatory fish that inhabit coral reefs and other warm coastal waters. They are opportunistic feeders and will consume crabs that venture too close. The Nassau grouper in particular is known for feeding on spiny lobsters, crabs, and other crustaceans.
Their powerful jaws allow them to easily crush the hard shells of crabs.
| A study in the Bahamas found that up to 16% of the Nassau grouper’s diet consisted of crabs. |
Other grouper species such as the red grouper, gag, and scamp also feed on crabs when the opportunity arises. In fact, crabs made up 11% of the identified prey items in the stomachs of gag groupers sampled in one study. Groupers are ambush predators that use camouflage near structure to surprise unwary crabs.
They suck crabs into their large mouth and swallow them whole.
Eels
Moray eels are fearsome predators that hide in reef crevices and corals, waiting to ambush prey. They have a second set of jaws in their throat called pharyngeal jaws that allows them to swallow large prey.
Crabs make up a regular part of the moray eel’s diet. In one study, crabs constituted 25% by volume of the moray eel’s stomach contents.
Moray eels have extremely flexible bodies that allow them to enter tight spaces and extract hiding crabs. Their rear-facing teeth also prevent crabs from escaping their grip. Smaller eel species may target crabs more frequently as a main food source.
Larger morays also eat fish, octopuses, squid, and other available prey.
Octopuses
Octopuses are cunning hunters that can capture crabs hiding in cracks and crevices with their dexterous arms. The common octopus and giant Pacific octopus regularly feed on a variety of crab species. One study found that crabs made up 25% of the common octopus’s diet.
Octopuses are well-suited for hunting crabs thanks to their ability to squeeze into tight spaces, powerful beaks for crushing shells, and intelligence for problem-solving. They may remove a crab’s claws before eating the body to avoid being pinched.
An octopus will eat small crabs whole while larger specimens are dismantled piece by piece.
Crabs That Eat Other Crab Species
Crabs are opportunistic omnivores that will eat almost anything they can get their claws on. This includes plant matter, mollusks, worms, and even other crabs. Cannibalism is quite common among crab species as they constantly scavenge for food. The most notable crab cannibals include:
1. Blue Crabs
Blue crabs (Callinectes sapidus) are aggressive predators that feed on bivalves, fish, plant matter, and even smaller blue crabs. Up to 20% of a blue crab’s diet can consist of juvenile crabs of the same species.
The larger mature crabs will attack the soft-shelled juveniles shortly after molting when they are vulnerable. This offers easy nutrition for the cannibals.
2. Fiddler Crabs
Male fiddler crabs are known for their single oversized claw that looks like a fiddle. However, this claw makes them top-heavy and prone to falling over. If this happens, other crabs may swarm over the helpless crab and dismember it.
Fiddlers also dig burrows for shelter which sometimes collapse and trap crabs inside — easy meals for any hungry passerby.
3. Coconut Crabs
The coconut crab (Birgus latro) is the world’s largest terrestrial arthropod, weighing up to 9 lbs. They are supreme omnivores that will attack and consume injured or dying coconut crabs. Their massive pincers can exert a grip force of over 3,300 newtons – easily enough to crush a crab shell and access the meat inside.
4. Spider Crabs
Spider crabs such as Japanese spider crabs live in dense colonies of up to 100,000 individuals. Food and shelter can be scarce, leading to competition and cannibalism, especially among molting crabs. Spider crabs also exhibit sexual cannibalism in which the female eats the male after mating.
Conclusion
In conclusion, crabs face predators from many types of animals including birds, mammals, reptiles, fish, and even other crabs. Some of the most common crab eaters are seagulls, raccoons, sea turtles, groupers, and octopuses.
The type of crab preyed upon depends on the crab species available in the predator’s habitat.
