Gerbils form the subfamily Gerbillinae, a large group consisting of over eighty species. They have a wide range of native land throughout most of Africa and parts of Europe, extending across Asia into Mongolia and China. Gerbils tend to live in arid areas, having adapted, in several ways, to the scarcity of water. By burrowing during the hottest part of the day, they protect themselves against dehydration. Then, at night they venture forth to forage for seeds and similar foods that, in the rapidly falling temperatures, gain a covering of dew. This provides the a vital source of fluid. Not surprisingly, the gerbil's digestive system is very effective at absorbing water and the kidneys are capable of producing a very concentrated urine, ensuring that vital water loss from the body is kept to a minimum.
The fur coat color of gerbils reflects their natural environment. Those which live in sandy areas, for example, may have very pale fur coats. The furred tail does have a darker bushy tip, however, and this may serve to confuse predators. Like some lizards, gerbils can lose part of the tail and survive, although it will not regenerate. The tail is an important piece of their anatomy, however, since it helps to provide balance for the body when the gerbil is standing on its hind legs or jumping. Indeed, they can jump considerable distances, relying on the powerful muscles at the top of their legs to provide the necessary impetus to clear long distances.
Similar to other creatures that live in open country with little natural cover, gerbils have very acute hearing, in spite of their rather small ears. The bony capsule that encloses the middle ear is greatly enlarged, and serves to amplify even the smallest sound. Their sense of vision is equally well developed. The eyes are prominent and positioned so as to provide a wide field of vision and give them the ability to detect the slightest movement nearby.
Gerbils are social creatures, living in groups. For part of the day they may even seal the entrances to their burrows. This helps to keep the internal temperature slightly lower, and may cause condensation of water droplets in the burrow. A typical colony may consist of up to three males and as many as seven females, with some juveniles coexisting in the group. They will forage collectively, digging if necessary for roots that can serve as an emergency supply of water.
Since an established group will not tolerate newcomers, it may seem that there would be a high degree of in-breeding within each colony, but studies of captive stock have revealed a unique system that avoids this need. Reproductively active females leave their colony and mate with a male of a neighboring group, before returning to the established family colony to give birth and rear their offspring. Since many species of gerbils live in remote and inhospitable areas of the world, however, we still have much to learn about their natural lifestyles.