Gerbils are also known as jirds or sand rats. The pet and laboratory gerbil is Meriones unguiculatus, commonly known as the Mongolian gerbil. The genus Meriones contains 14 species.
Externally, gerbils are quite ratlike. The head-and-body length is 95–180 mm; the tail length is 100–193 mm. On average, females weigh 70–100 g, and males weigh 80–130 g. The covering of fur on the tail is short near the base and progressively longer toward the tip, so it is slightly bushy. Coloration of the upper body varies from pale, clear yellowish through sandy and gray. The sides of the body are generally lighter than the back.
Wild Mongolian gerbils are found in Mongolia, adjacent parts of southern Siberia and northern China, and Manchuria. Gerbils inhabit clay and sandy deserts, bush country, and arid steppes. They have a high degree of resistance to heat stress and dehydration. They are terrestrial, and wild Mongolian gerbils construct simple burrows (2–3 feet long) in soft soil, where they spend most of their time.
Biology of Gerbils
Mongolian gerbils have several coat colors. The wild coat color, agouti, is controlled by an autosomal dominant gene. Sandy gerbils have a recessive color gene and show a yellow to ginger color on the dorsum and the typical creamy white belly of a wild-type Mongolian gerbil. The dorsal yellow hairs have short black tips and a light-olive-green base. A clear demarcation line separates dorsal and ventral colors. Black gerbils have an autosomal recessive gene; white albino gerbils with red eyes also have an autosomal recessive gene.
Gerbils have a large, ventral abdominal marking gland that is androgen dependent. It attains greater size and develops at an earlier age in males than in females. The gland is used for territorial marking. Females mark their territory after parturition and become more aggressive.
The gerbil's adrenal cortex produces nearly equal amounts of corticosterone and 19-hydroxycorticosterone. Compared with body weight, the weight of the adrenal gland is approximately 3 times greater in gerbils than in rats. A high proportion of RBCs in gerbils show polychromasia, basophilic stippling, and reticulocytosis.
Male gerbils attain sexual maturity by the age of 70–84 days. The vaginal opening in females develops between 40 and 60 days, sexual maturity occurs 30 days later. Gerbils tend to pair-bond, and often, an older female that has lost her mate will not accept another mate.
Early-maturing females are more likely than later-maturing females to breed successfully on first pairing, and the lifetime fecundity of early-maturing females is more than twice that of their late-maturing littermates. Two-thirds of the early-maturing females that do not reproduce after a first pairing will become pregnant after a second pairing, but only 10% of late-maturing females do so.
The gestation period of nonlactating gerbils is 24–26 days; however, lactating females always have a prolonged gestation of ≥ 27 days. If females are bred in the postpartum period, implantation is delayed, and gestation can take up to 48 days.
The litter size of gerbils ranges from 3 to 7. Young gerbils suckle for approximately 21 days and begin to eat solid foods at approximately 16 days. In general, day 25 is considered suitable for weaning.
The normal lifespan of a gerbil is 2–3 years.
Husbandry of Gerbils
The diet of wild Mongolian gerbils consists of green vegetation, roots, bulb seeds, cereals, fruits, and insects. Gerbils hoard food and are not normally coprophagic, unless their diet lacks adequate nutrients.
Gerbils thrive on commercially available pelleted rodent diets with 18–20% protein. They can have deficiency problems when fed primarily homemade diets, sunflower seeds, or table scraps, which lack specific nutrients.
Sunflower seeds are high in fat and low in calcium. Pelleted chow (5–8 g/day) has been recommended (1). On diets containing > 4% fat, gerbils develop high blood cholesterol concentrations, which manifest as lipemia that is more pronounced in males (2).
Gerbils excrete little urine, and their fecal pellets are hard and dry. Consequently, gerbil cages require less frequent cleaning than do the cages of other pet and laboratory rodents.
Gerbils adapt to a wide range of ambient temperatures. Because they have a propensity to develop nasal dermatitis at relative humidities > 50%, low humidity is advisable.
Gerbils require sand bathing to keep their coats from becoming oily. The lipids that gerbils produce have two sources: Harderian gland nasal excretions spread by self-grooming and sebaceous exudates from the skin. Lipid removal by sand bathing has multiple consequences: it not only cleans and grooms the coat but also deposits lipids on the substrate that act as olfactory signals.
Sand bathing also has homeostatic consequences. Hair color lightens in Mongolian gerbils allowed to sand-bathe.
Sand bathing is usually completed within 5 minutes.
When a gerbil is prevented from sand-bathing, accumulating hair lipids mat the fur, and the animal's behavior changes. Gerbils deprived of sand bathing increase their frequency of “sand rolls” (rolling onto their side or back and returning to their feet within 1 second), decrease grooming, and increase territorial marking (especially males).
Gerbils often stand erect on their hindlimbs, so their cages must have a solid bottom and the floor-to-lid height must be sufficient to accommodate this behavior.
Pet gerbils kept in inferior cages painted with lead paint or constructed with alloys containing lead have a high potential to develop chronic lead toxicosis because of their gnawing behavior and the urine-concentrating ability of their kidneys. In chronic cases of lead toxicosis, gerbils become emaciated, livers are small and pigmented, and kidneys are small and pitted. Microscopically, acid-fast inclusions are noted in the proximal collecting tubules and hepatocytes.
Physical Examination of Gerbils
Physical examination of a gerbil should begin with noting its overall appearance and behavior, particularly as compared with its cagemates. Sick animals are often isolated from others and might demonstrate weight loss, hunched posture, lethargy, rough fur, labored breathing, and a loss of exploratory behavior.
Early signs of disease involve changes in the color, consistency, odor, and amount of urine and feces. The perineal area should be checked for fecal or urine stains or, in females, discharges from the vulva. Fecal samples can be taken for parasite detection and bacterial culture.
The physical examination should also include the following:
The fur and skin should be examined for alopecia, fight wounds or other trauma; for ectoparasites; and for elasticity (evidence of dehydration).
The oral cavity should be checked for overgrown teeth.
The ears and eyes should be examined for discharges or inflammation.
The feet should be examined for sores and overgrown or broken nails.
The abdomen should be palpated for masses.
Body temperature should be checked. (Normal body temperature is 37–39°C [98–102°F].)
Respiratory rate or signs of labored breathing should be noted.
The thorax should be auscultated with a pediatric stethoscope.
Gerbil tails are fragile. To avoid injury, only the base of the tail should be grasped during handling.
Infectious Diseases of Gerbils
Bacterial, Mycoplasmal, and Rickettsial Infections in Gerbils
“Facial eczema,” “sore nose,” and "nasal dermatitis" all describe the same common skin condition in gerbils, caused by increased Harderian gland secretion of porphyrins. Porphyrins are thought to act as a primary skin irritant, because gerbils that have their Harderian glands surgically removed do not develop this condition.
Gerbils with nasal dermatitis display signs of initial erythema around the external nares, which can progress to localized alopecia and extensive moist dermatitis. Stress factors such as environmental humidity > 50% or overcrowding cause excessive Harderian gland secretion. Nasal dermatitis infection can extend to the maxillary sinuses, causing more severe clinical signs of anorexia, adipsia, weight loss, and even death.
The distribution and nature of lesions are useful for diagnosing nasal dermatitis in gerbils. Accumulated porphyrins fluoresce under UV light (Wood’s lamp). Routine bacteriology can isolate pathogenic staphylococci (Staphylococcus aureus and Staphylococcus xylosus).
Nasal dermatitis is treated by carefully cleaning the skin lesions and administering topical or parenteral antimicrobials (except streptomycin, which has been shown to be fatal when administered to gerbils) (2). Prevention requires lowering environmental humidity below 40% and decreasing sources of stress such as overcrowding or inability to sand-bathe.
Naturally occurring Tyzzer disease, an enterohepatic disease caused by the obligately intracellular bacterium Clostridium piliforme, is the most frequently described fatal infectious disease of gerbils. Common clinical and pathological findings are sudden death or death after a short period of disease and the presence of multiple foci of hepatic necrosis, respectively. Diarrhea and necrotic lesions in the intestinal tract are also possible.
Naturally occurring infection by C piliforme most likely occurs by the fecal-oral route, because gerbils exposed to infected bedding contract Tyzzer disease.
For gerbils with Tyzzer disease, supportive fluids and prophylactic administration of doxycycline (5 mg/kg, PO, every 12 hours for 7–10 days) or metronidazole (20 mg/kg, PO, every 12 hours for 7–10 days) are recommended to decrease mortality rates in cagemates (3).
Because the bacteria form spores, the housing environment should be thoroughly sanitized and disinfected. Spores are most readily inactivated by using appropriate disinfectants and allowing adequate contact time with the surface. Dilute bleach (1:10) or peracetic acid (1%) with a contact time of 5 minutes is adequate (4).
Mongolian gerbils are susceptible to infection by Helicobacter pylori, which causes severe gastritis, gastric ulceration, and intestinal metaplasia. Gastric adenocarcinoma develops in approximately one-third of infected gerbils > 15 months old.
Fatal enterotoxemia resulting from infection by Clostridioides difficile (formerly Clostridium difficile) has been associated in gerbils with treatment using nutritionally balanced triple-antimicrobial wafers (containing amoxicillin, metronidazole, and bismuth) to eliminate naturally occurring Helicobacter infections (5). Affected animals are reported to die within 7 days after antimicrobial administration.
Viral Infections in Gerbils
Naturally occurring viral infections of gerbils are not reported.
Parasitic Infestations in Gerbils
The pinworm Dentostomella translucida is the major nematode found in Mongolian gerbils. D translucida is commonly found in the small intestine of gerbils, and it has a direct life cycle with a prepatent period of 23–29 days (6). On average, there are four D translucida individuals per gerbil; however, no clinical signs are associated with infection.
Successful treatment of pinworms in gerbils using fenbendazole, either in medicated feed (150 ppm fed every other week for 9 weeks [7]) or in an oral paste (12 mg/kg, once [8]), has been described.
Gerbils are considered transitory hosts for the pinworms Syphacia obvelata and Syphacia muris, which are found normally in mice and rats, respectively.
Infections with the dwarf tapeworms Hymenolepis diminuta (9) and Rodentolepis nana (syn Hymenolepis nana [10]) are reported in pet gerbils. Common clinical signs include dehydration and mucoid diarrhea.
R nana has a direct life cycle and can infect humans if ingested. Recommended treatment is niclosamide fed at 10 mg feed/100 g body weightfor two 7-day periods separated by 1 week (11). Also effective are thiabendazole (0.33% mixed in feed for 7–14 days [12]) or praziquantel (30 mg/kg, IM, SC, or PO, once, repeated after 10 days [13]).
Pet gerbils have been reported with infestation by the tropical rat mite (Ornithonyssus bacoti) (14), which is also a zoonotic agent.
There are two reports of Demodex spp in gerbils. In one case, a 4-year-old debilitated gerbil developed alopecia, hyperemia, scaliness, and ulcerations at the base of the tail (6). Although mites were recovered from these regions, it is unclear whether the mites were the primary cause of the lesions. Treatment for Demodex sp have not been described for gerbils.
Fungal Infections in Gerbils
There are no reports of naturally occurring or experimental dermatophyte infections in Mongolian gerbils. Other fungal infections in Meriones spp are exceedingly rare.
Metabolic and Nutritional Disorders of Gerbils
Gerbils develop spontaneous, insidious periodontal disease after 6 months on standard rat/mouse diets. On the same diets, approximately 10% of gerbils become obese, and some show decreased glucose tolerance, increased serum immunoreactive insulin, and diabetic changes in the pancreas and other organs.
Pearls & Pitfalls
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To avoid these problems, always feed gerbils diets labeled specifically for their species.
Traumatic Injuries of Gerbils
Thin skin covers the tail of the gerbil. Unlike mice, if a gerbil is picked up by the tip of its tail, the skin will often slip off (degloving injury), leaving a raw, exposed tail that eventually becomes necrotic and sloughs.
If a gerbil sustains a degloving injury, exposing underlying soft tissue and bone, amputation of the bare portion of the tail as soon as possible is recommended to prevent the development of infection.
Iatrogenic Conditions of Gerbils
A fatal syndrome of acute toxicosis can occur in Mongolian gerbils after injection of a penicillin-dihydrostreptomycin-procaine combination. The toxicity is due to the dihydrostreptomycin component; 50 mg of dihydrostreptomycin produces almost 100% mortality in adult gerbils (2).
Approximately 20–40% of gerbils injected with dihydrostreptomycin develop reflex, stereotypical epileptiform (clonic-tonic) seizures starting at approximately 2 months old. Animals seize in response to sensory stimulation and forced exploratory behavior. The incidence and severity of these seizures vary; in general, though, the seizures pass in a few minutes, can be mild or severe, and have no lasting effects.
Although the incidence and severity of seizures due to toxicosis from dihydrostreptomycin often decrease with age, certain subsets of adult gerbils do not improve with age but have progressively more severe seizures.
The susceptibility of gerbils to toxicosis from dihydrostreptomycin occurs in selectively bred lines; however, pet gerbils can also be susceptible. Seizures can be suppressed in genetically predisposed gerbils if they are frequently stimulated by handling during the first 3 weeks of life. Anticonvulsant therapy is unnecessary.
Cystic ovaries occur frequently in Mongolian gerbils. Cysts range in diameter from 1 to 50 mm. Removal of the affected ovaries does not greatly affect reproductive performance.
Female gerbils that have only one ovary are slightly inferior in fertility compared with normal females. A general decline in fertility might be evident in older females.
Neoplasia of Gerbils
Studies of Mongolian gerbil laboratory colonies have reported a high incidence of spontaneous neoplasia, with a 25–40% incidence in gerbils > 2–3 years old (15, 16).
Squamous cell carcinomas of the sebaceous ventral marking gland in gerbil males and ovarian granulosa cell tumors in gerbil females account for 80% of tumors in animals > 3 years old (2). Ventral marking gland tumors invade locally and can metastasize to lymph nodes and lungs.
Adrenocortical tumors, cutaneous squamous cell carcinomas, malignant melanomas, and renal and splenic hemangiomas are the next most commonly reported tumors in gerbils. Numerous other tumors, including duodenal and cecal adenocarcinomas, hepatic lymphangiomas, hemangiomas and cholangiocarcinomas, splenic and renal hemangiomas, uterine leiomyomas and hemangiopericytomas, ovarian teratomas, testicular teratomas, and malignant melanomas, have also been reported. However, the total incidence of these tumors is < 5% (2).
Case reports of spontaneously occurring tumors in pet gerbils include infiltrative craniopharyngiomas (17), histiocytic sarcomas (18), systemic mastocytoses (19), malignant melanomas (20), and astrocytomas (21).
Miscellaneous Disorders of Gerbils
Congenital Disorders of Gerbils
Neonatal gerbils occasionally have ventricular septal defects.
Age-Related Disorders of Gerbils
Two separate reviews have reported pathological findings in aging Mongolian gerbil colonies (9, 22). Besides neoplasia, there was a high incidence of chronic glomerulonephropathy and focal myocardial degeneration and fibrosis, especially in older male gerbils.
Mongolian gerbils have a remarkable propensity for the development of aural cholesteatomas. They occur in 50% of gerbils > 2 years old.
Cholesteatomas in the ear canal displace the tympanum into the middle ear. Clinical signs in gerbils include head tilt. Compression and secondary infection result in bone necrosis and inner ear destruction.
Zoonotic Risk of Gerbils
There are no specific reports of zoonotic disease transmitted by pet Mongolian gerbils; however, pet gerbils infested with Ornithonyssus sylviarum (the northern fowl mite) and Dermanyssus gallinae (the chicken mite) have been the source of avian mite dermatitis in children. Avian mite infestation is a rare cause of pruritic dermatoses in humans. The mites spend most of their life cycle on the avian host but can be transmitted to humans by direct or indirect contact.
Infestations of R nana and O bacoti, both of which can infect humans, have also been reported in gerbils (10, 14). The scarcity of reports might reflect either the absence of zoonotic disease in gerbils or their low popularity as a pet rodent.
Key Points
Degloving injury to the tail due to improper handling is common in pet gerbils. Tail amputation as soon as possible after the injury occurs is the recommended treatment.
Nasal dermatitis is a common condition in pet gerbils. Treatment should include providing topical and/or systemic treatment of secondary bacterial infections, decreasing humidity in the environment, decreasing stressors, gently cleaning the affected area, and limiting availability of sand baths until resolution.
For More Information
Miwa Y, Mayer J. Hamsters and gerbils. In: Quesenberry KE, Orcutt CJ, Mans C, Carpenter JW, eds. Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. 4th ed. Elsevier; 2021:368-384.
Turner PV, Wheler CL, Beaufrère H, Fabian N, Harkness JE, eds. Harkness and Wagner's Biology and Medicine of Rabbits and Rodents. 6th ed. John Wiley & Sons; 2025.
Heatley JJ, Harris CM. Hamsters and gerbils. In: M Mitchell, Tully TN Jr, Manual of Exotic Pet Practice. Saunders Elsevier; 2009:406-432.
Also see pet owner content regarding gerbils.
References
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Morrisey JK, Carpenter, JW. Formulary. In: Quesenberry KE, Orcutt CJ, Mans C, Carpenter JW, eds. Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery. 4th ed. Elsevier; 2021:620-630.
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