Terrestrial crab facts for kids
Land crabs are special types of crabs that mostly live on land. While many crabs live in the ocean, land crabs have learned to survive far from the water. You can find them in families like Gecarcinidae and Gecarcinucidae. Some people use "land crab" to mean only the Gecarcinidae family. One example is the Johngarthia lagostoma crab from Ascension Island. It's the biggest native land animal there!
Living on Land
Crabs show different levels of how much they live on land. Some are "semi-terrestrial," meaning they spend time both on land and in water. Others are truly "terrestrial," living almost entirely on land. Most land-adapted crabs still need to go back to water to lay their eggs.
Amazing Journeys
Some land crabs live many kilometers from the sea. But they must make long trips back to the ocean each year. This is so they can lay their eggs. For example, after the Indian Ocean monsoon rains, the Christmas Island red crab (Gecarcoidea natalis) makes a huge journey. Thousands of crabs move together, forming a "living carpet" of crabs. These crabs can travel up to 1.46 kilometers in a single day! Their total journey can be as long as 4 kilometers.
Crabs That Don't Need Water
Only a few land crabs do not need to go back to water to reproduce. Some Geosesarma species are like this. The mother crab carries her eggs until they hatch into tiny, fully formed crabs. These young crabs are ready to live on land right away. Many crabs from the Potamidae family, which are mostly freshwater crabs, have also learned to live on land. Some, like the Tiwaripotamon genus, don't even need fresh water to have their babies.
How They Live
Many land crabs first evolved from freshwater crabs. This is because the changes needed to live in fresh water also helped them get ready for living on land. On some islands, land crabs are at the very top of the food chain. This means they are important predators and help control other animal populations.
