The gerbil is a small rodent, similar in many ways to by the mouse and the hamster. Gerbils have a long tail like a mouse which the gerbil is able to shed should the tail get trapped. This self defense mechanism allows the gerbil to escape predators, leaving them with just a tail.
Wild gerbils are well known for building extensive networks of tunnels that the gerbils are able to hide and breed in. The gerbil only really comes to the surface of the ground when the gerbil needs to find food and water.
The long and releasable tail of the gerbil is around the same length as the gerbils body, but it appears to depend on the individual gerbil species. The gerbil uses its long tail to help the gerbil balance when the gerbil is standing on its hind legs.