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Coconut Crab Facts & Worksheets

Coconut Crab is a species of terrestrial hermit crab that is known for its ability to crack open coconuts

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The coconut crab, also known as Birgus latro, is a terrestrial hermit crab with powerful pincers capable of cracking open and eating coconuts from palm trees. They can weigh up to 4.5 kilograms, making them the largest terrestrial arthropods ever recorded.

See the fact file below for more information on the Coconut Crab, or you can download our 29-page Coconut Crab worksheet pack to utilize within the classroom or home environment.

Key Facts & Information

Description

  • Robber crabs, or coconut crabs, are giant nocturnal land crabs native to the southwest Pacific and Indian oceans. Comparable to the hermit crab and the king crab, its relatives. 
  • Octopod crustaceans comprise the entire group. The average adult coconut crab is 1 meter from claw to claw. The adult can be any shade from pale violet to dark brown or deep purple. Juveniles and young adults are brown with black stripes along their legs.
  • Coconut crabs are omnivores that consume anything from decaying fruit and carrion to the shells of other crabs for their calcium content.
  • One of the coconut crab’s most recognizable abilities is to open coconuts with its enormous pincers. Their pincers can generate a maximum of 3,300 newtons of force. Coconut crabs can open coconuts by dropping them from trees and repeatedly striking them with their pincers, piercing the husk, and then splitting the seed.

Physical Characteristics

  • Juvenile coconut and hermit crabs hide within mollusk shells for shelter until they are too huge to fit. At this stage, an individual’s abdomen tucks partially under its body, where a set of hardened tergal plates protects it. Most coconut crabs have a dark blue shell; however, individuals from different populations and regions of the world may have different amounts of blue and redder or purple-red in their bodies.
  • Leathery skin with tufts of tiny bristles cover the rest of the core. The chelae (claws) of coconut crabs are asymmetrical, with the left being more prominent than the right. In addition, they can hold onto tree bark and other surfaces with the help of the dactyls on both sets of their lengthy pereiopods or legs.
  • They also have a second, smaller group of limbs, which the female uses to care for her eggs and the male uses to deliver sperm. Male coconut crabs are larger in size than females.
  • Males have an average carapace length of 75 mm, while females have an average of 50 mm. Females have three large, feathery pleopods located ventrally on their abdomens. These pleopods are used to transport egg masses.

Geographic Range

  • Coconut crabs are terrestrial hermit crabs found in the western part of the Indo-Pacific. They inhabit the islands of Mauritius, the Aldabras, Pitcairn, Tuamotu, and Easter Island in the Pacific, and Madagascar, Seychelles, and Aldabra in the Indian Ocean. Tanzania also hosts a sizable population.
  • Naturalist Charles Darwin believed they were only on “one coral island north of the Society group.” Although coconut crabs live on many Pacific islands, they are not particularly common everywhere. 
  • According to research, they previously lived on the Australian mainland, nearby islands, and probably India but are now extinct in those locations. Adult coconut crabs are unable to swim; therefore, planktonic larvae must have first colonized the islands.
  • Large communities of coconut crabs inhabit many of the Cook Islands, including Pukapuka, Suwarrow, Mangaia, Takutea, Mauke, Atiu, and Palmerston Island.
  • These, along with the Kiribati Line Islands, are close to the Gambier Islands, the eastern limit of its range, and in Kiribati, where the coconut crab is especially frequent on Teraina (Washington Island), with its abundant coconut palm forests. 

Behavior and Ecology

Habitat

  • Within a range of 0 to 6 kilometers from shore, coconut crabs are found in coastal settings on oceanic islands or small islets near bigger continental islands. Their burrows into the substrate serve as hiding places and food caches. While molting, these crabs may burrow as deeply as possible into the ground. Coconut crabs spend most of their time on land as adults, but their offspring develop in the water.

Behavior

  • Coconut crabs are nocturnal creatures that occasionally emerge to forage at dawn or dusk. However, on islands with heavy human populations, they are nocturnal only. Using their long legs, they can climb trees up to two meters high in search of food. Although they avoid physical conflict, these crabs appear to establish hierarchies based on body size. The only times an individual will leave their burrow is to seek food or mating.
  • Crabs that inhabit larger ones are nomadic and will often dig up and relocate. Coconut crabs dig holes up to a meter long when it’s time to molt, and they’ll stay there from three weeks to sixteen weeks (longer for more giant crabs). The crabs will overeat and pump out more hemolymph in preparation for this period. The crab will eat its exoskeleton once the molting process is complete.

Lifestyle

Reproduction

  • Mating takes place on dry soil, and either partner doesn’t need to have recently shed their skin. Unlike most hermit crabs, no apparent courtship activity has been recorded in this species. 
  • The male crab grasps the female’s chelae with his own and forces her to lie on her back. As the female moves, the male spermatophore transfers to her gonopore, allowing the sperm to enter her spermatheca. 
  • Ova undergo internal fertilization, and the resulting fertilized, orange eggs are passed out of the body onto the pleopods. 

Development

  • A female uses her pleopods to transport her eggs until they hatch. There is a 25-29 day window within which an egg can develop. 
  • There have been records of crabs with 45-day development times; the release of their larvae is timed to coincide with high tides. When the time comes, the pregnant female swims to the intertidal zone, where she shakes her eggs into the water.
  • Once the eggs come in contact with the water, the larvae will emerge. The four or five zoeal stages that larvae go through take between 17 and 28 days to complete. 
  • Timeframes range from 5–6 days for Stage 1, 3–5 days for Stage 2, 3–18 days for Stage 3, and 6–12 days for Stage 4. The fifth instar larvae is a mysterious stage about which little is known. After 21–28 days as a larva, the glaucophane (amphibious) phase begins. 
  • Their lungs become extremely vascularized at this stage. Before their protective tergal plates emerge, juvenile gastropods continue to rely on their shells for safety. Coconut crabs have a long lifespan, maturing to their full size after 40 to 60 years.

Diet

  • Coconut crabs consume other planktonic larvae when they are still planktonic. Unfortunately, we have no idea what glaucophytes consume. Carrion, molted exoskeletons of other crustaceans, tropical fruits (especially pandanus fruits, one of their principal food sources in many locales), and coconut meat have all been recorded in the diets of adults.
  • Each crab has its strategy for cracking open a coconut in search of its tasty flesh. A crab might crack open a coconut if it were to carry it up a tree and then drop it. Additionally, coconut crabs have been observed using their claws to puncture the coconut through the “eyes,” causing it to split. As an alternative, a crab may use its claws to smash open the coconut. Coconut crabs will carry large prey items to store in their underground homes. 

Role and Conservation

  • Coconut crabs help disperse the seeds of coconut trees by scavenging the fruit then discarding them rather than taking it back to their burrow to eat.
  • Competition may exist between coconut crabs and other terrestrial crabs with similar habits, such as the Coenobita species; this is usually indirect, and if approached, a Coenobita crab is likely to withdraw.
  • The International Union for the Conservation of Nature and Natural Resources has classified coconut crabs as “data insufficient.” 
  • These creatures are not currently threatened or endangered, but due to their slow growth rate and ease of capture, they are vulnerable to overharvesting.

Coconut Crab Worksheets

This fantastic bundle includes everything you need to know about the Coconut Crab across 29 in-depth pages. These ready-to-use worksheets are perfect for teaching kids about Coconut Crab, a species of terrestrial hermit crab that is known for its ability to crack open coconuts.

Coconut crab worksheets
Coconut crab worksheets
Coconut crab worksheets

Complete List of Included Worksheets

Below is a list of all the worksheets included in this document.

  • Coconut Crab Facts
  • Enormous Facts
  • Fact Or Bluff?
  • Word Search
  • Birgus Latro
  • Decapoda
  • Coconut Nut
  • FAQs
  • Compare And Contrast
  • The Palm Thief
  • Wildlife

Frequently Asked Questions

What is a coconut crab?

The coconut crab (Birgus latro) is a species of terrestrial hermit crab that is known for its ability to crack open coconuts. This species is the largest land-living arthropod and is found in the Indian Ocean and the western Pacific. They have a distinctive appearance, with a red or purple colored body and large pincers.

How big can a coconut crab grow?

Coconut crabs can grow quite large, with some individuals reaching up to 1 meter in length and weighing up to 4.1 kg. This makes them one of the largest arthropods on the planet. They grow continuously throughout their life and can live for several decades.

Where are coconut crabs found?

Coconut crabs are native to the Indian Ocean and western Pacific and can be found on several islands, including Christmas Island, Seychelles, and the Chagos Archipelago. They are typically found in forests, cliffs, and caves near the coast and are most active at night.

What do coconut crabs eat?

Coconut crabs are omnivores and feed on a variety of foods, including fruits, nuts, seeds, and shells. They are particularly known for their ability to crack open coconuts, which they do by climbing trees and dropping the coconuts onto rocks to crack them open. They will also feed on dead animals and other organic matter when available.

Are coconut crabs endangered?

Unfortunately, yes. Coconut crabs are considered endangered due to habitat destruction and over-exploitation for their meat. In addition, they are also threatened by introduced predators and competition for food. Conservation efforts are underway in some areas to protect their habitats and to regulate the harvest of these crabs for food. However, much more work needs to be done to ensure their survival and protection.

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Link will appear as Coconut Crab Facts & Worksheets: https://kidskonnect.com - KidsKonnect, January 31, 2023

Use With Any Curriculum

These worksheets have been specifically designed for use with any international curriculum. You can use these worksheets as-is, or edit them using Google Slides to make them more specific to your own student ability levels and curriculum standards.

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