Gerbils (i.e. Mongolian gerbils) are small rodents, with long furry tails with a tuft of fur at the end. They are larger than mice, but smaller than typical hamsters (syrian hamsters, not dwarf hamsters). The wild type coloration is "agouti", where each hair is banded, usually gray next to the skin, then a yellowish color, then ticked with black, with off-white hair on the belly. However, through selective breeding, several lovely color variations are available.
In their dry native habitats of Asia and Africa gerbils have few natural enemies and seem more curious than fearful of humans. The Mongolian gerbil, the most common species sold in stores, is a born burrower and will develop networks of tunnels with food storage, nesting, and sleeping sites. Gerbils are four to six inches long excluding the tail and have a lifespan of three to five years.
The gerbil family is made up of roughly 100 species. These are 14 basic groups of gerbils. The species most commonly kept as pets is the Mongolian Gerbil, whose scientific name is Meriones unguiculatus. Gerbils whose scientific name begin with "Meriones" are also known as "jirds" which roughly means "large desert rodent." The Mongolian gerbil is therefore also known as the Clawed Jird. Other jirds also kept as pets include Sundevall's Jird (Meriones crassus), the Libyan Jird (Meriones libycus), and Shaw's Jird (Meriones shawi). Shaw's Jird is large, even tempered and makes a good pet, and when fanciers use the term jird they are often referring to this species. Therefore, the term "gerbil" most commonly refers to the Mongolian Gerbil, and the term "jird" most commonly refers to Shaw's Jird. Confused? There's more: There are two other species of gerbil which do not belong to the genus Meriones, but that are also referred to as jirds. These are the Bushy Tailed Jird (Sekeetamys calurus), and the Fat Tailed Jird (Pachyuromys duprasis). However, these are more commonly referred to as the "bushy tail" and the "duprasi" respectively. There are many other species of gerbil, some of which are less commonly kept as pets, but they are too numerous to cover here.