What Does the Coconut Crab Eat? The Surprising Diet of This Giant Land Crab

The coconut crab, also known as the robber crab or palm thief, is a fascinating creature. As the largest land-dwelling arthropod in the world, it grows to be over 3 feet wide and can weigh up to 9 pounds! But what exactly does this giant crab eat to get so big?

In this article, we’ll take a look at the surprising diet and eating habits of the amazing coconut crab. From coconuts and fruits to carrion and other crabs, these giant land crabs are omnivorous scavengers that will eat just about anything!

The coconut crab (Birgus latro) is a species of hermit crab that can be found across the tropical Indian and Pacific Oceans. Unlike other hermit crabs, the coconut crab grows out of its borrowed mollusk shell as it matures.

Juvenile coconut crabs carry shells for protection just like regular hermit crabs. But once they grow larger than the shell, their back hardens into a tough exoskeleton. This allows the crab to grow much bigger than a typical hermit crab.

Coconut crabs have two large front claws – the left one is usually bigger than the right. They have four sets of walking legs, with the rear pair adapted to hold eggs. Their bodies are divided into the front cephalothorax section and abdomen.

While they need to reproduce in the ocean these giant crabs live their adult lives on land. Their adaptations allow them to survive just fine on the coastal areas of tropical islands and beaches.

So what exactly does the coconut crab eat with those giant claws? Let’s find out!

Coconuts Are Not Their Favorite Food

While named after the fruit, coconuts are not the coconut crab’s primary food source. They will eat coconut meat and are capable of cracking open coconuts. However, coconut flesh comprises a small minority of their diverse diet.

Coconut crabs use their massive claws, which are strong enough to lift over 750 pounds, to break through the hard shell. They will also climb trees and drop coconuts to break them open on rocks below.

Still, coconut meat isn’t their favorite food. The crab got its name from the fact that they are commonly found in areas where coconuts grow, not because coconuts are their main diet.

Fruits, Seeds, and Nuts Are Their Staple Foods

The coconut crab’s primary diet consists of fleshy fruits, nuts, and seeds that have fallen to the ground in their tropical habitat.

Some examples of their favorite foods include

• Fleshy tropical fruits like bananas, mangoes, papaya, pineapple, and more
• Nuts like coconuts, almonds, chestnuts
• Seeds from trees and plants
• Germinated coconuts

They will also eat the pith of recently fallen trees and various plant materials Their massive claws allow them to cut, shred, and access the internal flesh and nutrients.

Overall, any type of fallen fruit, seed pod, or nut is likely to get eaten by a hungry coconut crab. They play an important role as scavengers that help break down plant matter and redistribute nutrients on the forest floor.

They Are Opportunistic Scavengers

In addition to fruits, nuts and seeds, coconut crabs are opportunistic omnivores. They will eat just about any organic materials they can find, making them important scavengers in their ecosystem.

The coconut crab’s diverse opportunistic diet includes:

• Carrion and dead animals
• Scraps left behind by humans
• Dead fish and other marine animals washed up on shore
• Animal dung
• Other small slow-moving animals like ants
• Molted exoskeletons of other crabs and arthropods

Essentially, if they come across an easy meal, the coconut crab will eat it. They provide an important cleanup service in their habitats by eating decaying organic matter.

Their keen sense of smell allows them to quickly locate food sources. Coconut crabs will even climb or knock down rotting fruits hanging in trees to access the nutritious interior.

They Sometimes Prey on Other Animals

Coconut crabs are mostly scavengers, meaning they eat dead plant and animal matter. However, large adult coconut crabs are opportunistic predators and will eat live prey if given the chance.

Examples of live animals coconut crabs will prey upon include:

• Other smaller crabs like hermit crabs, which are eaten after molting their soft shells.
• Slow-moving snails, worms, starfish and other marine animals they come across.
• Carrion that has died recently, including dead birds, rats and sea turtle hatchlings.
• Turtle eggs and rotting eggs.
• Baby birds, rodents, lizards and other small vertebrates.
• Even adult sea birds in some rare cases.

Their massive claws can easily crush the shells and bones of smaller animals. Documented cases of coconut crabs preying on species like rats and seabirds demonstrate their formidable predatory abilities.

Essentially, any small or slow-moving animal that crosses a coconut crab’s path may become a meal. This makes them one of the top predators in their ecosystem.

Cannibalism Occurs When Food is Scarce

In times of food scarcity, coconut crabs will even resort to cannibalism and eat each other. Larger crabs will prey on younger, smaller crabs if desperate for food.

Molting crabs are especially vulnerable to cannibalism, since they have soft shells during this period. Coconut crabs will also consume the molted exoskeletons of other crabs to recycle nutrients.

Cannibalism seems to be a relatively common foraging strategy. In laboratory experiments, about 25% of coconut crabs resorted to cannibalism when starving.

Their Diverse Diet Changes As They Grow

The diet of coconut crabs changes across their life stages:

• Larvae: Feed on plankton floating in the ocean.
• Juveniles: Act like hermit crabs, scavenging anything they can find. Their small claws limit them to soft foods.
• Adolescents: Expand diet to plant matter like leaves, fruits and seedlings.
• Adults: Capable of consuming hard-shelled nuts, coconuts, and small animals thanks to their massive claws.

So while the food options are limited for early life stages, adult coconut crabs become versatile generalist feeders. Their diverse diet is likely one reason they are able to grow to such massive sizes.

They Play a Key Role in Seed Dispersal

An interesting aspect of the coconut crab’s diet is their role in dispersing seeds and nuts across their environment.

They often carry fallen fruits and nuts back to their burrows. Coconut crabs cannot digest the tough shells or fibrous husks. So seeds often pass through their digestive systems intact.

The crabs distribute these undamaged seeds throughout the landscape as they defecate. This is important for helping plants proliferate and spread to new areas.

So in effect, the coconut crab’s feeding habits combined with their mobility helps propagate their ecosystem’s flora. They serve as an unusual yet effective seed dispersal agent!

Their Diet Highlights Their Evolutionary Adaptations

The remarkable diet of the coconut crab highlights some of their key evolutionary adaptations for surviving on land:

• Powerful claws for tearing, crushing and gripping food. Allows them to access hard nuts and seeds.
• Broad salivary glands to help digest food.
• A highly sensitive sense of smell to locate food sources like carrion.
• Ability to climb trees and rocks to reach food in hard-to-access locations.
• Hardened exoskeleton that provides protection and water retention, unlike the shells used by other hermit crabs.

Many of the coconut crab’s unique physical and behavioral adaptations have evolved to allow it to take advantage of food resources in its harsh terrestrial environment.

Their reputation as robber crabs comes from their propensity to steal or eat any unattended food, earning them a reputation on some islands. While not picky eaters, they play an important ecological role distributing seeds, nuts and recycling nutrients across their coastal forest ecosystem.

The coconut crab’s varied diet and adaptations showcase how animals evolve to take advantage of ecological opportunities. This is what allows the world’s largest land arthropod to thrive on the tropical coastlines it calls home.