The Mongolian gerbil is a small rodent that originates in Mongolia and Northern China. It measures approximately 5 inches from mouth to base of the tail, with a tail of around 3/4 of the body length. Males are slightly larger than females. One of the most striking features of a Mongolian gerbil is that, unlike mice and rats, they have a tail covered in hair and that ends in a tuft.
Mongolian gerbils are desert animals, so they consume little water. As consequence, they also urinate in small amounts. This makes gerbils rodents that produce little smell in their cages.
Gerbils are crepuscular animals. This means that they are active both during the day and the night, with the biggest periods of activity at dusk and at dawn.
In the wild, gerbils are agouti in color (brown with black ticking and white bellies). In captivity, a series of mutations have appeared, allowing for all sorts of colors like black, dove, argente, grey agouti, siamese, burmese, dark eyed honey, and a lot more.

Gerbils are social animals, so it's important to get two to live together. A lonely gerbil is likely to develop depression, obesity and not be as active as it would be if it had a partner. Gerbils can live in same sex groups or in mixed sex pairs. It is important to remember that if you place a male with a female they will breed. Males can live together in pairs or groups with little or no problem as long as enough space is provided for them. Females are more territorial than males, and tend to fight in large groups, so it is advised to house females only in pairs. If you get a pair of gerbils they will bond for life, but this doesn't mean that they won't bond to you if they are paired. As a matter of fact, a gerbil that has a gerbil companion is more outgoing and tends to make friends with it's owner more easily than a lone gerbil. A lone gerbils is usually scared, because it feels unprotected (safety in groups).
Gerbils are highly territorial animals, so if you place 2 adults that don't know each other, they will most likely fight. Introductions should be done very carefully and will be discussed in this section.