Background

The golden hamster in the wild occupies an area from Romania and Bulgaria southeastward through Asia Minor, the Caucasus, Israel, and northwestern section of Iran. In the wild these animals live on bushy slopes and steppes. General coloration above is light reddish brown and beneath is white and creamy. One form has a distinct ashy stripe across the chest. The skin of these animals is quite loose and the enormous cheek pouches which open inside the lips extend well back of the shoulder. When filled, they more than double the width of the animal's head and shoulders. (The Arabic equivalent of "originator of saddle bags" is given these pouches.) The Golden Hamster is essentially nocturnal in habit though they may be active at times during the day. The animals generally live alone in extensive burrows of their own making and will fight others of their kind although families often live together in harmony in close quarters. In captivity, these animals soon become tame and, like most laboratory animals, can be handled easily but with caution. They have little or no body odor and are remarkably free from disease. In the wild they will defend themselves when frightened but when assured that harm does not threaten they become docile. They appear to be almost omnivorous, eating many kinds of green vegetables, seeds, fruit, and meat. Although originally described in 1839, little was known about them until 1930 when a male and 2 females with twelve young were obtained in Syria and brought to Israel. It is from this stock that all present domesticated stocks and strains have been developed. These animals were first brought to the United States in 1938. The Syrian hamster was quickly accepted as a valuable laboratory tool and utilized in several studies in the 1930's and 40's.

Anatomical and Physiologic Characteristics

Although hamsters are not true hibernators, with shortened day length and temperatures of 5C to 15C they gather food and pseudo-hibernate for extended periods of time.

On either flank, usually buried in hair and always more prominent in males, lie dark brown patches known as flank glands. These sebaceous glands are used to mark territory and contribute to the stimuli determining mating behaviors.

The hamster has a fore stomach, anatomically linked to the esophagus, is the site of some pre-gastric fermentation.

The urine has a pH of about 8, turbid and milky in appearance because of large number of small crystals it contains.

Antibiotics can be and generally are fatal. Do not use them.

Newborn hamsters have fully erupted incisor teeth. The incisors are used in nursing to strip milk from the teats of the dam while suckling. Hamsters have 3/3 molars with fixed roots and 1/1 open rooted incisors (Means they continually grow and should be checked regularly to ensure proper occlusion.) No canine or premolar teeth are present.

Behavior

Hamsters have an undeserved reputation for pugnacity, a characteristic usually exhibited only after rough handling or a sudden disturbance. Hamsters, even those recently captured in the wild, are readily tamed, although they remain remarkably adept at chewing on and escaping from their cages. Escaped hamsters will not return to their cages, as will rats and gerbils. The use of live traps or a ramp leading into a bucket placed against a room wall may be necessary to catch an escaped hamster. Hamsters are most active during the dark and enjoy wheel-running activity. Pregnant females are reported to run up to 8 km per day.

Except for the few hours of estrus occurring once during the 4-day cycle, the sexually unreceptive female will usually attack a recently introduced male. Following copulation, the male is frequently removed from the breeding cage. Hamsters may be grouped by sex (males and females separate) in holding cages. Hamsters fight less often if housed together at the time of weaning or before sexual maturity, awakened simultaneously from anesthesia in a neutral arena, or provided with bolt holes or hiding places. Females may fight other females, and less often, males may fight other males.

The female hamster, when excited, is able to conceal her newborn litter in her cheek pouches. Later, when the perceived danger has passed, the mother returns the young to the nest; however, young may suffocate in the cheek pouch. Females may also conceal feed or bedding and other objects in their cheek pouches. Females with litters should be disturbed as little as possible.

Life span

Female hamsters produce 5 to 6 large litters and then produce smaller litters for another 6 to 9 months, or until the dams are 12 to 15 months old. Males are used for commercial breeding until 12 months of age, but pet males may serve longer. Hamsters usually have a life span of 18 to 24 months, but older individuals are frequently reported. See below for sexing hamsters.

Housing

Several acceptable types of hamster cages are available, some equipped with wheels, tunnels, and nest boxes. In research colonies, hamsters are usually housed in plastic, solid-bottom cages with deeply piled wood shavings for bedding. Such components are also desirable in pet hamster homes. Because hamsters have blunt noses, they may have difficulty eating from the slotted, sheet metal hoppers used for mice and rats and from wire mesh feeders. When the slots are large enough for the hamster to eat through comfortably, it will nevertheless pull the food pellets into the cage. Hamsters chew plastic, wood, and soft metals and will readily escape from a poorly secured or constructed cages. Transport boxes are usually lined with mesh or light metal screening.

An adult hamster (over 100 g) requires a floor area of at least 123 cm2 (19 in.2) and a cage height of at least 15cm (6 in.). A female breeding hamster should have 790 cm2 (150 in.2) Of floor space. Adult hamsters are housed in temperatures between 18 degrees and 29 degrees C with a suggested level of 18 degrees to 26 degrees C (65 degrees to 79 degrees F). The young are maintained at 22 to 24 degrees C (71 degrees to 75 degrees F). The relative humidity should be between 40% and 70%. The 12:12 light:dark cycle is most often used, but other lighting arrangements have been used successfully.

Hamsters produce little waste or odor, but in research colonies, hamster cages are changed twice weekly, except when neonates are present. Cages are sanitized with hot (82 degrees C or 180 degrees F.) water with or without a detergent or with nontoxic disinfectant and a thorough rinse. Bottles and hoppers are cleaned at the same time as the cages.

Feeding and Watering

Although the nutritional requirements of the omnivorous hamster have not been specifically determined, a pelletize rodent diet containing approximately 16% protein and 4 to 5% fat is conveniently used until better information is available. Protein deficiency may cause alopecia, while dietary fat above 7 to 9% may increase morality. Laboratory rodent feeds are often repackaged in small, unlabeled bags and sold in pet stores. The low-protein but attractively wrapped "treats" may not be adequate diets for growth and reproduction. Never feed milk products or high carbohydrates such as sweets because they will hold them in their pouch which can lead to tooth decay.

Dams with litters should receive their feed directly on the floor, as preoccupation with hopper-bound pellets may result in neglect of the young. Young hamsters begin gnawing solid food and drinking water at 7 to 10 days of age; therefore, the sipper tube should extend low in the cage but not into the bedding. Feeder slots should be greater than 11 mm wide. Hamsters eat 5 to 12 g feed (about 2 tsp) and drink 10 ml (1/2 oz.) water per 100 g body weight daily.

Experimental Uses

The unique feature of the hamster, the reversible cheek pouch, provides a site for normal and abnormal tissue transplants that have the virtue of visibility and ready access. In some studies a tumor maintained in one cheek pouch was exposed to an experimental treatment while the control tumor was maintained in the opposite cheek pouch.

The Syrian Hamster, despite his aggressive behavior and bad temperament has been used in a number of studies involved in experimental tumor production, hormonal effects on reproduction, dental carries, nutritional studies, cardiovascular and pharmacological research, as well as research in infectious disease and pathological investigation.

Source of information:
The Biology and Medicine of Rabbits and Rodents, John E. Harkness and Joseph E. Wagner. Hamsters, Compiled originally by the Laboratory Animal Medicine Department, Uniformed Services University of the Health Sciences.

HAMSTER