There are some pretty large animals in the world. Giraffes are notable for their long necks, and whales for their sheer size, but have you ever seen the biggest crab in the world? Coconut crabs are the largest living terrestrial invertebrates on Earth. This video by BBC Earth shows off these amazing crabs. Read below to learn more about the coconut crab.
The coconut crab is massive.
©iStock.com/BrianScantlebury
All About the Coconut Crab
Coconut crabs are the largest land-dwelling arthropod on Earth. Known scientifically as Birgus latro, and more commonly as the robber crab, these crabs are native to different tropical islands across the Indian and Pacific Oceans. Some of the islands include Christmas Island, the Cocos Islands, Fiji, Tonga, and many more. The crab’s size is what they’re famous for, with an adult typically weighing between 5 and 9 pounds. Their leg span can reach up to about 3 feet (1 meter), while their body (carapace) is usually much smaller. With great size also comes great strength, as they are amazing climbers, using their long legs to traverse different surfaces. Their claws are extremely strong and can pinch with a force of up to 3,300 newtons, making them among the strongest of any animal relative to their size.
Coconut crabs are omnivores and scavengers, meaning that they feed on a variety of things. These include nuts, fruit, small live animals, insects, and seeds. They get their nickname “robber crab” from their affinity for shiny or smelly items. They steal items from the trash, as well as silverware, thinking that they are edible or interesting to look at. They get their other name from the coconuts they eat, using their powerful claws to crack them open. After cracking a coconut with their claws, they can peel the outer husk to reach the meat inside. While they may be good at cracking coconuts, it often takes them hours to eat one.
Why Are They So Big?
Coconut crabs are so large as a result of a biological phenomenon called island gigantism. Island gigantism results from several environmental factors. First, on islands without predators, having a large body is not a disadvantage, so there is no evolutionary pressure against growing large. Second, islands often have an abundance of food for the animals on them. Third, creatures like coconut crabs have slow metabolisms and long lifespans, which contribute to their large size. This results in slow growth over decades and increasing sizes through generations. Lastly, niche evolution is unique to each animal that undergoes island gigantism. For these crabs, the lack of competition for food on the island has resulted in them being the main scavengers. On other islands, these are often raccoons or wild pigs.
Because of their giant size, the coconut crab can live a very long life as well. Coconut crabs are estimated to live around 40 to 60 years. Mating happens on land for these crabs as they are terrestrial. The female crabs will release their fertilized eggs into the ocean, where the larvae will hatch. After hatching, the larvae will grow for a few weeks before crawling onto land and beginning their life as terrestrial organisms. After crawling on land and finding a shell to live in, they will molt repeatedly over decades, getting bigger and bigger each time until they die. During their life, they will act as cleaning scavengers responsible for eating other dead and decaying plant and animal matter. This behavior helps maintain the ecosystem, especially for plants, as coconut crabs disperse seeds and aerate the soil.
The post Meet the Largest Terrestrial Invertebrate on Earth appeared first on A-Z Animals.
