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Biology of the Gerbil
Biology of the Gerbil
Origin and Habitat
Mongolian gerbils (desert rat, sand rat, antelope rat, jird) are native to eastern Mongolia, northeast China, and western Manchuria. They live in a variety of terrains, including deserts, bush country arid steepes, low plains, grasslands, and mountain valleys. Gerbils are gregarious, active during both day and night, and build extensive burrows, often with several entrances. The diet consists of seeds, leaves, stems, and roots; to some extent food is stored in burrows. In 1954, eleven pairs were brought to the United States from a research laboratory in Japan. The offspring of these gerbils were the nucleus for most research colonies in the United States today.
As research animals, gerbils comprise less than 0.5% of the total number of rodents used annually. As pets, gerbils are popular because they are curious, clean, and easy to maintain and handle. Most research gerbils are agouti, popular colors of those kept as pets are agouti, white, and black. At least three inbred strains are available.
A gerbil is easily lifted by scooping it up in one’s hands, where it usually remains without restraint. A gerbil can also be lifted by grasping the base of the tail to move the animal from one enclosure to another. Grasping the tail other than at the base and lifting may result in slippage of the skin and subcutaneous tissue, and subsequent necrosis, infection, and sloughing of the caudal vertebrae.
Another technique suitable for lifting and restraining the gerbil is to place the hand over the gerbil’s back, placing the second and third fingers on either side of the head and the thumb on the ventral body wall. Restraint can also be performed by grasping the loose skin over the neck/shoulder area with one’s thumb and forefinger. The gerbil is then lifted, the palm is inverted, and the tail can be restrained with the other hand if necessary.
Anatomy and Physiology
Adult body weight:
70 - 100g (female); 30 - 110g (male)
Life span: 3 - 4 years
Respiratory rate: 90 breaths/minute
Heart rate: 360 beats/minute
Normal average rectal temperature: 102ºF
Gerbils should be fed a commercial gerbil, hamster, or rodent diet. They readily accept and prefer sunflower seeds to a pelleted diet, but feeding sunflower seeds (low in calcium) can lead to a nutritional imbalance. Although gerbils require little water, it should be provided ad lib.
Food intake is approximately 5-8g/100g BW/day; water intake is approximately 4-7 ml/100g BW/day.
Breeding onset is between 65-85 days of age in females (although first estrus may occur at 35 days) and 70-85 days in males. Gerbils are polyestrous and breed year round; ovulation is spontaneous. The duration of the estrous cycle is 4-6 days. Vaginal smears are useful for determining the stage of the estrous cycle, but this technique is not commonly employed, as gerbils used as breeders are permanently paired (they form stable lifelong monogamous pairs). Mating is usually, but not always, nocturnal. A copulatory plug is formed but is not easily detected; the presence of sperm on a vaginal smear is a better indicator of mating.
The average gestation period is 25 days. A fertile postpartum estrus occurs in 60-85% of gerbils, and simultaneous lactation and gestation may prolong gestation up to 42 days due to delayed implantation. The average litter size is 4-6. The young weight approximately 3 grams at birth, are hairless, and have closed eyelids and ears. Cannibalization is rare; if it does occur, the litter is usually small and is the dam’s first. The young are weaned at 21 days; weaning weight is 20-25 grams. If the postpartum estrus is not utilized, the dam resumes cycling following weaning.
Newborn male gerbils are distinguished from newborn female gerbils by noting the greater anogenital distance in the males. This is best accomplished by lifting the tails of littermates and comparing perineums.
It is unknown whether pseudopregnancy occurs in the gerbil.
Diseases of the Gerbils
Bald Nose, Sore Nose: Harderian gland hypersecretion with
Neoplasia (Gerbils older than 2 years)
skin cancer (melanomas and squamous cell carcinoma)
benign adenomas of scent glands.
Humidity greater than 50% causes increased Harderian gland secretion, animals appear wet from excess grooming, fur dries and mats.
Pine or cedar shavings can cause matted, greasy fur.
Due to overcrowding.
Base of tail and crown of head most common barbering sites.
Decreased appetite and muscle mass
Drinking lots of water
20%-40% occurrence in normal population.
Seizures triggered by fright, handling, etc.
Can be clonic or catatonic.
Usually have a rapid recovery.
No treatment is necessary.
Very Toxic to gerbils
Affected animals show ascending paralysis with 80%-100% mortality
Do NOT use this drug in gerbils.