Crabs live in the water, which includes the oceans, rivers, lakes and ponds; most crab species are fond of freshwater. Crabs come in different sizes, ranging from a few millimeters to up to 12 feet. Even though they live in water, crabs sometimes venture to land, and certain species, such as the robber crabs, can even climb trees.
Crabs are one of the oldest species on the planet. Although male and female crabs look alike, it is possible to tell the difference by observing under the shell. Males have an elongated spire in the center of the shell while females have a triangular shape area. Male crabs also have longer claws than females.