The most common pet gerbil is the Mongolian gerbil. Its scientific name, Meriones unguiculatus, is a reference to the Greek warrior Meriones who went into battle wearing a helmet adorned with boar's teeth. The so-called "warrior with claws" thrives in the flatlands of the African and Asian steppe, where it digs long burrows as shelter from the day's heat. Unlike hamsters, whose wild cousins are also desert dwellers, gerbils are not strictly nocturnal rodents. Instead, they are active in the morning and the evening, avoiding the extremes of both hot and cold.
Gerbils were brought to the United States from Asia in 1954. They were touted as excellent small pets for children because they are naturally curious and social animals, and do not bite people unless scared or mishandled. Gerbils emit very little waste and thus are clean and relatively odorless additions to the household. With proper care, gerbils live between two and four years in captivity.
There are more than 85 gerbil species in the wild. Gerbils are often called jirds, which is an adaptation of an Arabic word that means large desert rodent. Several of the gerbil's physical characteristics favor the dry, desolate and sometimes harsh landscape that gerbils thrive in. They have efficient kidney systems that help them retain most fluids they get from eating seeds, roots and plant shoots to cope with the relative scarcity of water. They can pick up on sounds as small as a bird's wings flapping through the air. The wild gerbil's sand-colored hair is naturally oily as a guard against dry conditions. His large dark eyes are less bulbous and protruding than other small rodents, but don't be fooled by the gerbil's sleepy look; he is always alert and has excellent peripheral vision. Pet store gerbils retain most of these qualities, though you are likely to find domestic gerbils in a number of different colors including lilac, cinnamon, black, white, and spotted combinations of those colors.
A gerbil's burrow is usually located less than two feet underground, but may reach up to 40 feet in length. The average burrow is between 15 and 20 feet in length with a central nest and several openings to surface level. These entrances serve as escape routes for gerbils fleeing from Eagle owls and other birds of prey. Sometimes gerbils dig tunnels that connect to the burrows of neighboring gerbil pairs and their litters. Adult male gerbils are highly territorial creatures. The larger and heavier the gerbil "warrior" is, the more property he's likely to scent-mark and stake out for his family. If confronted by a strange gerbil, a territorial gerbil may fight the intruder to the death, using his sharp front teeth as weapons.
Gerbils are very social animals, and it is best to keep them in pairs or groups. Ideally, a small group of siblings is best, because family groups are usually fond of each other. Keep the sex the same, however, unless you plan on breeding. They will play, chasing each other around, wrestling and boxing. They will also groom one another, sleep in piles and cuddle together. Unfortunately, they may also fight and it is difficult to distinguish fighting from regular play. Often one animals will appear distressed and the activity will appear more intense than usual.
Gerbils communicate by thumping their strong back legs against the ground or whistling sharply. They thump when they are excited or stressed as a warning to other gerbils. Often when one gerbil is startled and begins thumping, others will also begin thumping. It varies in loudness and tempo, depending on the urgency or meaning, but it can be quite loud. A warning alarm struck against the ground is passed along by other gerbils that receive the warning and repeat it. Young gerbils may do a lot of thumping, too, but it is just a learning activity. Thumping is also part of the mating system.
Like prairie dogs, gerbils can stand alert on their back legs. They can also use those back legs to leap more than 18 inches horizontally. Gerbils use their long fur-covered tails for balance when they jump. A gerbil's tail is usually the same length his body (between four and five inches for most Mongolian gerbils) but he can lose all or part of that tail as a defense mechanism, much as a lizard can. Once severed, a gerbil's tail does not regenerate.