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Gerbils: The Basic Facts

Dorothy Robichaud, ACT Department of Physiology Queens University Kingston, Ontario. Canada

Gerbils are becoming popular pets because of their minimal care, friendly disposition, and curious nature. They are clean and odorless because of their grooming habits, and they have scant urine and fecal output. Because veterinary technicians are increasingly likely to encounter gerbils in veterinary clinics, they need to be acquainted with the basic physiology (Table I), behavior, and principles of good care of these fascinating pets.

History

Gerbils are jumping desert rats found in Asia, Africa, and parts of Eastern Europe. There is scant information about gerbils' life in the wild, except that they are burrowing animals that live far from water sources and eat seeds, grains, grasses, roots, and plants found in their desert environments

These rodents were first imported into North America in 1954 for use in research. Qualities that made them useful in medical studies include their slight water requirement, their heat tolerance and body temperature regulation, their adjustment to high?fat diets, their relatively high resistance to radiation exposure, and an unusual abdominal sebaceous gland. Since 1954, they have increased in popularity and now are kept as household pets because of their unique characteristics, ease of care, and gentle disposition.

Gerbils belong to the order Rodentia, the family Cricetidae, and the subfamily Gerbillinae, which consists of about ten genera and some 100 species. The two most common species are the Mongolian gerbil (Meriones unguiculatus) and the Egyptian gerbil (Gerbillus gerbillus).

Appearance and Behavior

Mature gerbils are smaller than rats but larger than mice. Mongolian gerbils generally have reddish brown fur with black outer tips on their backs, but coat color can vary from tan to gray with a gray or creamy white undercoat (Figure 1). Also available now are black gerbils with touches of white under the chin and on the feet, and albinos. The head is broad and short, with proportionately sized ears and large, black, slightly bulging eyes. The hindlegs are elongated, and the forefeet are relatively small. Each foot has long, thin, black nails. The Egyptian gerbil is similar but has a slimmer body and a more pointed nose.

Gerbils alternate periods of intense activity with sleep or rest day and night. Normal activities include burrowing, scratching, gnawing on available material, making nests, and nibbling on food continually to support their bursts of energy. Movements are short, quick, and jerky, like those of chipmunks. Gerbils are not cuddly animals but do enjoy being handled; they rarely bite. Because of their curious nature, any new object is investigated immediately.

Nutrition

Because their food preferences are quite adaptable, gerbils can eat all commercial laboratory rodent chows. A typical diet consists of alfalfa and soymeal pellets, barley, cracked corn, sunflower seeds, oats, and wheat. A digestible protein content of approximately 15 % is recommended. Dry feed should be supplemented with fresh fruit and green vegetables several times a week. Fresh water always should be available. The average gerbil eats about 10 to 15 grams of food and drinks 3 to 4 ml of water per day. Baby gerbils nurse from their mothers until approximately three weeks of age (weaning time), when they learn to eat solid foods. Vitamin drops or cod liver oil can be given to ensure adequate supplies of required nutrients.

TABLE I

Physiologic Data

Housing

Gerbils seem happiest and most active when kept in pairs male-female, female-female, or even male-male.Two mature males or females raised in different families might fight occasionally if kept together. The temperature of the environment should be approximately 15º to 24ºC (59° to 75°F) with 40% to 50% relative humidity. Homemade or purchased cages, made of sheet metal, plastic, glass, or wire mesh, can be used. Wood cages are less sanitary and can be gnawed. Dimensions of approximately 15 cm wide by 15 cm high by 30 cm long are adequate for a pair. Solid cage sides, which reduce scattering of bedding material, are preferable. A wire mesh lid is necessary because of gerbils' excellent jumping ability. The bedding material itself should have a depth of 5 to 10 cm and can be made of pine shavings, cedar chips, crushed corncobs, shredded paper, or other small animal litter.

Because the incisors of gerbils grow throughout their lifetimes, blocks of wood or cardboard rolls and boxes can be given in addition to hard food to assist the wearing down process. If overgrowth, which can lead to breakage or misalignment of the teeth, becomes a problem, it might be necessary to have them cut by a veterinarian.

Exercise wheels can be provided to fulfill energy use needs (Figures 2 and 3). Occasionally, mazes are set up outside the cage for this purpose.

Editor's Note: A monogamous breeding pair should have breeding cage area of at least 900 cm.

Handling and Sexing

The preferred method of picking up a gerbil is by cupping one's hands under the animal's body (Figure 4). A d gerbil also can be lifted by grasping the base of the tail with one hand and supporting the body with the other. Sex markings usually are distinguishable by weaning time. The male has a tapered bulge near the base of the tail and a dark?colored scrotal sac. The female is more rounded caudally and has a shorter anogenital distance than the malez (Figure 5).

Preventive Health Care and Diseases

Gerbils are relatively healthy and hardy and will remain so with minimum care. Disease prevention is important because successful treatment of some diseases in gerbils is difficult. Protective measures include proper diet, fresh water, reasonable cleanliness, sufficient cage space and ventilation, and protection against dampness and extreme temperatures or drafts. No diseases unique to gerbils have been discovered, although few studies have been conducted in this tield. Diarrhea and intestinal disorders are rare and usually are related to diet rather than to bacterial disorders. Bacterial pathogens of gerbils include Pasteurella pneumotropica, Corynebacterium kutscheri, Citrobacter freundii, and Streptococcus pneumoniae. Gerbils have a natural susceptibility to acute infection with Salmonella organisms. They also are susceptible to Tyzzer's disease, a gastrointestinal tract disease caused by the gram negative rod Bacillus piliformis. Clinical signs of Tyzzer's disease are diarrhea, humped back, poor haircoat, and sudden death. Bacterial skin infections caused by Staphylococcus species can occur in which lesions and alopecia develop around the nose ("Red Nose") and spread to the legs and the abdominal region. The young are more susceptible.

External parasites, such as fleas, mites, and lice, can be a problem. Gerbils also can be infested with the zoonotic tapeworm Hymenolepis nana, a potential human health hazard. Cross infection from other laboratory animals can occur with Entamoeba muris and the pinworm Enterobius vermicularis. Tests indicate that the normal flora of gerbils poses no pathologic threat to humans. Spontaneous malignant tumors are reported occasionally in older gerbils.

Feasibility as Pets

Because of their cleanliness, ease of care, pleasant disposition, and curiosity, gerbils are enjoyed in the pet world. They can be left unattended for days if food and water are available. Gerbils also are quiet, making only faint, high pitched "chee-chee" noises when arguing; they also sometimes thump with their hindfeet when excited or frightened. Their pert expressions and quick movements are fascinating to watch. For these reasons, gerbils are recommended as entertaining companions.

Acknowledgment

The photographs appear through the courtesy of Guy Gingras, ACT.

REFERENCES

1. Guide to the Care and Use of Experimental Animals, vol 1. Ottawa. Canadian Council on Animal Care. 1980, pp 79-85.

2. Robinson DG: How to Raise and Train Gerbils. New Jersey, T. F. H. Publications, 1967.

3. Glen EM. Gray J: The effect of various hormones on the growth and histology of the gerbil abdominal sebaceous gland pad. Endoc rinoloKy 76:1115-1123. 1965.

4. The Diagram Group: Pets: Even Owner's Encvclopedia. Montreal, Optimum Publishing Co, pp 114-115.

5. HagenT" Hamster Food (also for white mice and gerbils). Montreal, Rolf C. Hagen Inc, information from feed bag.

6. Paradise PR: Gerbils. New Jersey, T. F. H. Publications, 1980, pp 80-82.

7. Siegmund OH (ed): The Merck Veterinarv Manual. Rahway. NJ, Merck & Co, 1979, pp 1188-1195.

8. Guide to the Care and Use of Experimental Animals, vol 2. Ottawa, Canadian Council on Animal Care. 1984, p 115-9. Hoff GL: Public health and gerbils: Microbial evaluation. JAVMA 179:1384, 1981.

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