A gerbil is a small mammal of the order Rodentia. Once known simply as "desert rats", the gerbil subfamily includes about 110 species of African, Indian, and Asian rodents, including sand rats and jirds, all of which are adapted to arid habitats. Most are primarily diurnal (though some, including the common household pet, do exhibit crepuscular behavior), and almost all are omnivorous.
One Mongolian species, Meriones unguiculatus, also known as the Clawed Jird, is a gentle and hardy animal that has become a popular pet. It was first brought to the United States in 1954 by Dr. Victor Schwentker for use in research.
Gerbils are typically between six and twelve inches (150 to 300 mm) long, including the tail which makes up approximately one half of their total length. One species however, the Great Gerbil, or Rhombomys opimus, originally native to Turkmenistan, can grow to more than 16 inches (400 mm) in length. The average adult gerbil weighs approximately 2 1/2 ounces. As of August 19, 2003, officials in western China's Xinjiang Uygur Autonomous Region began releasing eagles to combat the damage they say the great gerbils have done to eleven million acres (46,000 km²) of grassland.
The typical Mongolian gerbil is a desert species, and lives underground in a network of tunnels, which include chambers with families. Adults move away and meet others from other chambers, extend the network, create their own chamber, and breed. Gerbils come up for food and water; there is no evidence of hoarding food, but gerbils will eat a lot of fatty foods in one sitting, suggesting supplies in the form of fat reserves rather than food storage. Gerbils do not hibernate and are diurnal. Their long tails help them to balance when they stand up on their hind legs.
Gerbil movement is more like hopping than running, and their large back feet are furry on the bottom to protect them from the heat of the sand. Gerbils are fast but overly inquisitive. In their natural environment, they are mostly insectivores, and additionally gain moisture from desert plants that store water in them. A gerbil has fur all over its body, including the tail, as this prevents it from getting sunburned.
Normal gerbil behavior includes jumping, climbing, chewing, and digging. The digging motions are very common: the gerbil moves its arms rapidly.
They are curious and not easily startled. They love to burrow and hide.
Gerbils are social animals, and prefer to live in groups. Often very large groups live well together, as long as the living environment is big enough; otherwise, the gerbils may become frustrated and attack one another. Groups of females are much more quarrelsome than groups of males, but if fighting occurs among males it is usually much more vicious. Males will very rarely attack females.
Avoid lettuces, as the nitrates can prevent oxygenation of the blood, and citrus fruits, which are known carcinogens. Sugary treats are bad for gerbils; they rot the teeth and the sugar is hard for a gerbil to digest. Lastly, do not feed your gerbils food with high water content, such as celery or watermelon, as the water will cause the gerbil to have the runs, or "wet-tail" as it is commonly known.
Gerbils often have what looks like boxing matches; this is most common amongst young gerbils (gerbil "pups"). These are gentle play fights which usually end in the winner pinning down the loser and grooming it. However, if a pair of gerbils are fighting closely in a ball shape, with both gerbils biting deeply and drawing blood, careful but swift intervention is in order by the pet owner, using a jar or oven mitts to avoid getting bitten.
Gerbils like to sleep in a group, often on top of each other. Sometimes they will absentmindedly groom each other when half asleep. Gerbils have a form of purring called "bruxing" which they do when they are being groomed or while they enjoy being stroked in the hand by their owner.
Squeaks can occasionally be heard from them, and a squeak is usually an indication of annoyance. When another gerbil steps on another without thinking, it will give a squeak, or when a gerbil tries to steal another's food, it will turn with a squeak, and when a male tries to mate an unsuspecting female, she may well turn around sharply to face him and squeak at him. Gerbil pups will squeak more often when very young, sometimes when feeding or if they have strayed from the nest.
Gerbils will raise their hackles and arch their backs to show aggression, often turned to the side and leaning against the other gerbil's body. Usually this is a warning that a fight is about to occur, and if this behavior is observed it is wise to quickly intervene.
Gerbils will also alert each other to danger by thumping on their hind legs, usually triple thumps repeated in a steady sequence. Gerbils will also thump when sexually excited. Younger gerbils are more likely to start thumping than older ones.
Gerbils will mate for several hours, in frequent short bursts followed by short chases where the female allows the male to catch her. Once he catches her, the female will squeak and make flick motions to get the male off of her. Males will not attack females except in rare circumstances which may also include them having been separated from their original mates, or widowed. A female may attack a male, but usually he is more than a match for her.
Males generally are good fathers, helping wash them and such. Interestingly, usually only the mother returns a nestling to the nest if they stumble out. The other gerbils sniff them in order to identify them, but do not pick them up. Mothers can seem rather rough with their babies, picking them up awkwardly in her teeth, kicking the babies out the nest and back in again, and even stepping on them. This, however, is normal behavior by the mother. If a gerbil is eating its young, it will hold the infant in its hands like it would a piece of food, and run around with it.
The fur will grow thicker and longer, and by three weeks some of them may have one of their eyes open. Around this point, they begin to be weaned, eating food and not relying so much on milk. At this point, it would help to provide a soft food like an oat and milk mixture for them. The gerbils will become more active and their tails will lengthen and give them more balance so they can stand upright. When fully weaned and beginning to play fight with one another, they will soon be ready to move away, if required.
A mother will often be stern with how quickly the babies are weaned if she is expecting a new litter. A less fertile mother may let her litter suckle for longer. Older mothers often do not have as good a milk supply, and need plentiful water available to replenish it.
A litter will be of about 4-8 gerbils on average, although losses due to runts, defects and infanticide, or occasional, unexplainable persecution from other gerbils sometimes make the eventual litter one or two short.
The most common ways of checking the sex of a young gerbil are: 1) Turning the gerbil over and checking the gap size between the genital organs of the gerbil. Female gerbils have a small gap between the two areas, while males have a much larger gap. 2) Although not always clear in childhood and adolescence, male gerbils have a fur covered bulge at the base of their tails, on their underside. This is their scrotal pouch. Females have smooth, round back ends.
Males are generally larger than females in adulthood, in length, height, and width. A gerbil can also be sexed by looking at its underside when it is a blind, deaf baby. There will be either a thick line in the middle of the stomach (the scent marker) if it is a male, or eight dots (four on the left side, four on the right) (soon to be teats) if it is a female.
There are several reasons for the popularity of gerbils as household pets. The animals are typically non-aggressive, and they rarely bite unprovoked or without stress. They are small and easy to handle, since they are sociable creatures that enjoy the company of humans and other gerbils. Gerbils also have adapted their kidneys to produce a minimum of waste to conserve body fluids which makes them very clean with little odor.
The pets are incredibly industrious and will explore new environments, and they will build, construct, and enjoy elaborate networks of tunnels if given an environment that allows for it. This is easily observable as gerbils are active during all hours of the day, as opposed to the more nocturnal rodent pets. They can "recycle" everyday paper-based items, such as cardboard products like toilet paper tubes and brown paper bags, into toys and nesting material, chewing the material into small bits. If the chewed material is allowed to accumulate to a depth of 4-6 inches deep, they will tunnel through it.
There are many color varieties of gerbil available in pet shops today, generally the result of years of selective breeding.
There are over 20 different coat colors in the Mongolian gerbil, which has been captive-bred the longest.
Another species of gerbil has also been recently introduced to the pet industry: the Fat-tailed Gerbil, or duprasi. They’re smaller than the common Mongolian gerbils and have long soft coats and a short, fat tail, appearing more like a hamster. There is a variation on the normal duprasi coat which is more gray in color, which may be a mutation, or it may be the result of hybrids between the Egyptian and Algerian subspecies of duprasi.
White spotting has been reported in not only the Mongolian Gerbil, but also the Pallid Gerbil and possibly Sundervall's Jird.
A long-haired mutation, a grey agouti or chinchilla mutation, white spotting, and possibly a dilute mutation have also appeared in Shaw's Jirds, and white spotting and a dilute mutation have shown up in Bushy-tailed Jirds.