Hamster

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Hamsters are rodents belonging to the subfamily Cricetinae. The subfamily contains about 18 species, classified in six or seven genera. Because they are easy to breed in captivity, hamsters are often used as lab animals and kept as pets.

[edit] Habitat

Hamsters are indigenous to the Middle East, south-eastern Europe, and in the case of dwarf hamsters, Russia, Mongolia and China. ^[1] They typically burrow.

[edit] Diet

Hamsters are omnivorous. Fresh fruits and vegetables, seeds, and insects such as grasshoppers make up an important part of hamsters' natural diet.

[edit] Behaviour

Hamsters are crepuscular, though some will awaken during the day for short periods. They are also very territorial.

[edit] Reproduction

Hamsters become fertile at different ages dependent on their species, but this can be from 1 month to 3 months of age. Male hamsters remain fertile for the rest of their lives, though females do not. Females are "on heat" approximately every three days.

Gestation lasts 16-18 days for Syrian hamsters, 18-21 days for the Russian hamsters, 21-23 days for Chinese hamsters and 23-30 for Roborovski Hamsters. The average litter for Syrians is about 7, but can be as great as 24, which is the maximum number of pups that can be contained in the uterus. Campbell's Dwarf Hamsters tend to have 4-8 in a litter but can have up to 14. Winter White Russian Dwarf Hamsters tend to have slightly smaller litters, as do Chinese and Roborovski hamsters.

Hamsters are born hairless and blind in a nest which the mother will have prepared in advance. After 1 week they begin to explore outside the nest. They are completely weaned after 3 weeks, or 4 for Roborovski Hamsters. Most breeders will sell the hamsters to shops when the hamsters are anywhere as of about 2-8 months old.

[edit] Classification

Taxonomists currently disagree about the most appropriate placement of the subfamily Cricetinae within the superfamily Muroidea. Some place it in a family Cricetidae that also includes voles, lemmings, and New World rats and mice; others group all these into a large family called Muridae.

• Subfamily Cricetinae
  • Genus Allocricetulus
    • Species A. curtatus - Mongolian Hamster
    • Species A. eversmanni - Kazakh Hamster, also called Eversmann's Hamster
  • Genus Cansumys
    • Species C. canus - Gansu Hamster
  • Genus Cricetulus
    • Species C. alticola - Ladak Hamster
    • Species C. barabensis, including "C. pseudogriseus" and "C. obscurus" - Chinese Striped Hamster, also called Chinese Hamster; Striped Dwarf Hamster
    • Species C. griseus - Chinese Hamster
    • Species C. kamensis - Tibetan Hamster
    • Species C. longicaudatus - Long-tailed Hamster
    • Species C. migratorius - Armenian Hamster, also called Migratory Grey Hamster; Grey Hamster; Grey Dwarf Hamster; Migratory Hamster
    • Species C. sokolovi - Sokolov's Hamster
  • Genus Cricetus
    • Species C. cricetus - European Hamster, also called Common Hamster or Black-Bellied Field Hamster
  • Genus Mesocricetus - Golden Hamsters
    • Species M. auratus - Syrian Hamster, also called the Golden hamster or Teddy Bear hamster)
    • Species M. brandti - Turkish hamster, also called Brandt's Hamster; Azerbaijani Hamster
    • Species M. newtoni - Romanian Hamster
    • Species M. raddei - Ciscaucasian Hamster
  • Genus Phodopus - Dwarf Hamsters
    • Species P. campbelli - Campbell's Russian Dwarf Hamster
    • Species P. roborovskii - Roborovski Hamster, sometimes known as the Mongolian Hamster, causing confusion with Allocricetulus curtatus
    • Species P. sungorus - Winter White Russian Dwarf Hamster
  • Genus Tscherskia
    • Species T. triton - Greater Long-tailed Hamster, also called Korean Hamster

[edit] Pet ownership

The best-known species of hamster is the Syrian or Golden Hamster (Mesocricetus auratus), which is the type of hamster most commonly kept as a pet. It is also sometimes called a "fancy" hamster. Pet stores also have taken to calling them "honey bears," "panda bears," "black bears," "European black bears," "polar bears," "teddy bears," and "Dalmatian", depending on their coloration. There are also several variations, including long-haired varieties that grow hair several centimeters long and often require special care.

Other hamsters that are kept as pets are the four species of "dwarf hamster". Campbell's Dwarf Hamster (Phodopus campbelli) is the most common of the four — they are also sometimes called "Russian Dwarfs"; however, many hamsters are from Russia, and so this ambiguous name does not distinguish them from other species appropriately. The coat of the Winter White Russian Dwarf Hamster (Phodopus sungorus) turns white during winter (when the hours of daylight decrease). The Roborovski Hamster (Phodopus roborovskii) is extremely small and fast. The Chinese Hamster (Cricetulus griseus), although not technically a true "dwarf hamster", is the only hamster with a prehensile tail (about 4cm long) - most hamsters have very short, non-prehensile tails.

Many breeders also show their hamsters and so breed towards producing a good healthy show hamster with a view to keeping one or two themselves so quality and temperament are of vital importance when planning the breeding. Although breeders of show hamsters specialise in breeding show hamsters, there are also owners who have bred their pet hamsters. These may be the result of a planned or unplanned pregnancy but the hamsters have usually been cared for well and handled regularly, so make very suitable pets. Buying a hamster directly from a breeder means that there is the opportunity to see the parents and know the dates of birth.

In Australia it is illegal to keep hamsters as pets as 'escapees' could breed in the wild and become 'feral' pest animals.

[edit] Housing

Hamsters can be kept both in cages and in terraria, both of which are available in pet stores. Cages are easier to carry; their bars can be used for climbing. On the other hand, glass boxes keep hamsters from throwing litter out of their cages, provide a better view into the hamster's home, and create a quieter and more sheltered interior.

Despite the hamster’s small size, appropriate housing should always have a floor space of at least two square feet and a strong top because hamsters are surprisingly good climbers. Glass boxes must not be higher than their width to allow for a sufficient air circulation. Although smaller in size, dwarf hamsters often need more spacious housing than their larger relatives, at least 80cm by 40cm (2 feet by 4 feet) due to their high activity levels.

In the case of self-built dwellings, care should be taken to avoid materials that are dangerous to the animals. Plywood and wood from conifers is not suitable, because hamsters gnaw at their houses and both glue and resin are poisonous to them. Using standard water-soluble white wood glue to join pieces of solid wood, such as birch or beech wood, creates a safe environment for the hamster, although it may still chew through the wood. A purchased cage can be equipped with several intermediate levels, connected using stairs.

Hamsters do best in a well-lit room of constant, moderate temperature (18 to 26°C, 64 to 80°F), in a place out of strong sunlight that could cause dangerous overheating.

The floor of a hamster's residence is generally covered with a layer of litter. Litter made from recycled paper or wood lacking aromatic oils (such as aspen) is healthiest - gnawing and eating cat litter can be deadly, and cedar, pine, or other softwood-based litters may contain phenols that can irritate a hamster's respiratory system, liver, and skin. There is also commercial bedding available, such as Carefresh and Megazorb.

Syrian hamsters are the best to keep as pets, for they are easier to handle and train.

[edit] Exercise and entertainment

Like all pets, hamsters need exercise and entertainment to maintain their physical and mental health. "Exercise wheels" allow hamsters to run full speed, and are a common fixture in pet hamsters' enclosures. Avoid using wheels with individual rungs or bars, but rather select those with a solid base for comfortable running. This is because a hamster may trip and its legs may get caught on the rungs of the wheel while using it. Olive oil(which is harmless to a hamster if ingested) can be used to lubricate the axle of the exercise wheel to reduce friction and cut down on turning noises when in use. Other common objects are plastic balls or cars that the hamster can be placed in so that they can be supervised while exploring outside their cage. Lack of exercises for a hamster may cause it to suffer from paralysis, and the affected hamster will have a hunched over posture.^[2]

Hamsters are nest builders, so most owners supply strips of tissue or toilet paper so they may build a secure spot in a corner or in their "house". Avoid using newspapers as the ink on it might be ingested when the hamster chews on them. Hay is also a valuable building material for cozy hamster nests, but may pose the risk of having pesticides on it or sharp pieces that could cut or scratch the hamster. Therefore, select dry hay such as Timothy and use the softer, leafy parts of the hay rather than the stems. Sawdust made from pine is not suitable for nesting material as stated earlier. Lint from the dryer also works well. They will rip it apart and make a bed out of it. Fine chinchilla sand (not chinchilla dust because the powdery material will cause respiratory problems) can be given in an enclosed container. Hamsters enjoy rolling in the sand to keep their fur clean and dry.

Hamsters, like many rodents, are also gnawers, and must be supplied with appropriate materials for doing so; for example, an edible gnaw toy or an unpainted wooden block can be placed in the cage. Failure to do so can cause dental problems for the hamster, as the incisors, which grow continually, will become too long and cause discomfort and/or eating problems.

[edit] Food

Many hamsters tend to carry food from the source (by carrying it in their cheek pouches) and hoard it away in a cache hidden somewhere inside their container. Fresh vegetables and fruits, seeds, and insects like grasshoppers make up an important part of hamsters' natural diet. However, not all foods are suitable for hamsters and some, such as sweets made for humans or poisonous plants like the leaves of the tomato or rhubarb, are dangerous for hamsters. Citrus fruits such as oranges and lemons should never be fed to a hamster because their stomachs can not handle the acid. Iceburg lettuce has very little nutritional value and in excess can cause liver problems. Campbell's Dwarf Hamsters are susceptible to hereditary diabetes, and any hamster suffering from diabetes should not have high sugar foods, such as fruit and corn.

In detail, the solid food components can be divided into three categories: dry, fresh, and animal food. Dry food generally makes up the bulk of a hamster's diet. Besides the standard rodent food sold in pet stores, most other kinds of seeds, kernels, and nuts can be given. Bird food like millet is a noteworthy alternative for small hamsters.

[edit] Sex and longevity

Syrian hamsters typically live no more than two to three years in captivity, less than that in the wild. Russian Hamsters (Campbell's and Winter White) live approximately 1.5 to 2 years in captivity, and Chinese Hamsters 2.5 to 3 years. The smaller Roborovski Hamster often lives to 3 to 3.5 years in captivity. Both Syrian and Russian hamsters mature quickly and can begin reproducing at a young age (4-5 weeks), whereas Chinese hamsters will usually begin reproducing at 2-3 months of age, and Roborovskis at 3-4 months of age.

Left to their own devices, hamsters will produce several litters a year with several pups in each litter. Male and female hamsters are therefore usually kept in separate enclosures to prevent the addition of unwanted offspring. When seen from above, a sexually mature female hamster has a trim tail line; a male's tail line bulges on both sides. Male hamsters typically have very large testes in relation to their body size. Before sexual maturity occurs at about 4-6 weeks, it is more difficult to determine a young hamster's sex. When examined, female hamsters have two holes close together, whereas males have anal and genital openings further apart than the female's. (The penis is usually withdrawn into the coat and thus appears as a hole or pink pimple.)

[edit] Health conditions

[edit] Dental problems

Misalignment of incisors due to injury or malnutrition may result in overgrowth, which can cause injury to the roof of the mouth. Symptoms include a drop or loss of appetite, drooling, weight loss, or foul breath. The only cure is for a veterinarian to regularly trim the overgrown incisors and prescribe antibiotics.^[3]

[edit] Trauma

Common injuries are caused by hamsters being dropped or falling, usually while inside an "exercise ball", which can cause broken limbs or a fractured spine, for which there is no cure. Injured hamsters should be examined immediately by a veterinarian to determine the best course of action in each situation.^[3]

[edit] Trauma - Hot or Cold

Hamsters need to be kept in a temperature which is comfortable to most humans. This is good, but occasionally they can get too hot or too cold.

If a hamster is too hot, it may get heat stroke. An animal with heat stroke may be lethargic and limp. Its ears will be down. It might be sweaty or its fur may be matted. If you suspect heat stroke put your hamster in a cool location and mist it gently with cool water. When it seems revived, place it in his cage in a cool location and make sure it has plenty of cold water and cold moist fruits (such as apple) to replenish its fluids.

If a hamster is too cold, it may develop induced hibernation. In this state it won't be able to be easily wake up and is cold to the touch, he or she may die. Revive the hamster by handling it in a very warm location. Use a heater or a lamp or even the bathroom with hot steamy water running, but do not place the hamster's cage directly on the heating source or it could get too hot. After it is revived, keep it very warm for about ten hours and then make sure it is not chilled again.

If a too hot or too cold hamster is not revived by the above treatment within 20 minutes, it will need immediate emergency vet care. To avoid this trauma in the future:

1) Never place a hamsters cage in a window, on or near a heat source (even an infrequent one like a fireplace) or in a room that gets a lot of midday sun.

2) Never let your hamster cage sit directly on a cold surface like a cement floor. If you must keep your pet in the garage or basement, put its cage on a raised platform and provide insulation in the form of a blanket wrapped around the bottom third of the cage and taped securely with electrical tape.

3) If you think your hamster is getting too cold in the winter nights, provide extra nesting material and make sure it has a snug house inside his cage. Additionally you may want to aim a lamp at the cage which is a less expensive way to provide heat to a small area than a space heater.

4) The smaller the animal the greater the ratio of surface area to mass and the quicker the rate of heat loss. Consequently, hamsters are not as hardy as rabbits or guinea pigs and the cage is best kept indoors.

5) When in doubt, pick your hamster up. He or she should feel neither cold nor warm to the touch.

6) If you feel unable to take care of your hamster take it to an animal shelter as soon as possible.

[edit] Bladder stones

Hamsters are susceptible to bladder stones. Although the owner will typically not detect the stone, symptoms include frequent and painful urination, blood in urine, increased water consumption, and loss of appetite. Only a veterinarian can remove the stone and provide appropriate antibiotics.^[3]

[edit] Tumors

Tumors, both benign and malignant, are fairly common in pet hamsters, and are most common in older females. Usually, the tumors involve hormone-producing organs, causing hormone imbalances, hair loss, and changes in behavior. If it is an external tumor, a veterinarian can often perform surgery, but internal tumors are much more difficult to remove, since the animal is so small, so the owners typically elect not to operate, but, rather, to euthanize the pet.^[3]

[edit] Neglect

[edit] Wet tail

The most serious intestinal disease of hamsters is "wet tail", or proliferative ileitis, which is most common among weaning hamsters (3-6 weeks) and Syrian hamsters. Symptoms include lethargy, increased irritability, hunched posture, fluid or bloody diarrhea, a wet, soiled anal area and tail, and, sometimes, rectal prolapse. A veterinarian is needed to immediately examine and evaluate the situation and will usually treat the problem with fluid replacement, oral antidiarrheal medication, and antibiotics, although treatment is often unrewarding, and death may occur as soon as 48 hours after the onset of initial signs.^[3]

[edit] Salmonellosis

Several species of the bacterium salmonella can cause serious intestinal disease in hamsters and is transmittable to humans. The bacterium is usually acquired by eating contaminated food, especially fruit and vegetables, which can be avoided by thoroughly washing them before they are offered to hamsters. Treatment includes either antibiotics or euthanasia.^[3]

[edit] Demodectic mange

Demodectic mange is a common external parasite problem caused by mites that reside within the hair follicles and certain glands of the skin, with symptoms including scaly skin and significant hair loss, especially over the back. This disease can be treated, but the patient may have an underlying problem, such as kidney disease, for which there is no practical treatment or cure.^[3]

[edit] Rabies and lymphocytic choriomeningitis

Hamsters are not natural hosts of the rabies or lymphocytic choriomeningitis viruses, so a hamster can become infected with them if exposed to infected saliva from a natural host, such as a skunk, fox, or bat, although this is highly unlikely in captivity, as hamsters are indoor pets. Lymphocytic choriomeningitis is transmittable to humans, with symptoms such as recurrent fever, headache, fatigue, muscle aches, sore throat, rash, and arthritis. ^[3]

[edit] Intestinal parasites

Hamsters frequently harbor intestinal parasites within their small intestines:

• Tapeworm is the most common, causes weight loss and can be transmitted to humans through the animal's feces.
• Pinworms are less common and usually cause no signs at all besides itching of the anus and cannot be transmitted to humans.

Owners suspicious of either parasite problem will need to submit a fecal sample to a veterinarian for diagnosis. If there are eggs in the sample, treatment can be instituted by the veterinarian.^[3]

[edit] Eyeless whites

Anophthalmic whites, more commonly known as "eyeless whites", are all white hamsters that are born without eyes. These hamsters are produced when two white-bellied hamsters carrying the anophthalmic gene are used for breeding. The eyes are usually non-existent, but are sometimes rudimentary, or not fully developed. The hamsters are typically born deaf as well, and the life span of eyeless whites is around 9-12 months.

Blind hamsters are perfectly capable of survival, but they can be a lot more nervous than normal hamsters. Since hamsters usually have poor eyesight to begin with, blindness is not a huge handicap, although the animals are more difficult to tame, so an owner must use extra care. They will feed normally and are very active, although they may seem to lose all comprehension of time, and seem not to know if it is day or night.^[4]

[edit] Relationships Among Hamsters

Neumann et al. (2006) conducted a molecular phylogenetic analysis of 12 of the above 17 species of hamster using DNA sequence from three genes: 12S rRNA, cytochrome b, and von Willebrand factor. They uncovered the following relationships:

[edit] Phodopus Group

The genus Phodopus was found to represent the earliest split among hamsters. Their analysis included both species. The results of another study (Lebedev et al., 2003) may suggest that Cricetulus kamensis (and presumably the related C. alticola) might belong to either this Phodopus group or hold a similar basal position.

[edit] Mesocricetus Group

The genus Mesocricetus also form a clade. Their analysis included all four species, with M. auratus and M. raddei forming one subclade and M. brandti and M. newtoni another.

[edit] Remaining Genera

The remaining genera of hamsters formed a third major clade. Two of the three sampled species within Cricetulus represent the earliest split. This clade contains Cricetulus barabensis (and presumably the related C. sokolovi) and Cricetulus longicaudatus.

The remaining clade contains members of Allocricetulus, Tscherskia, Cricetus, and Cricetulus migratorius. Allocricetulus and Cricetus were sister taxa. Cricetulus migratorius was their next closest relative, and Tscherskia was basal.

[edit] Similar animals

Note that there are some rodents which are sometimes called "hamsters" that are not currently classified in the hamster subfamily Cricetinae. These include the Maned Hamster or Crested Hamster, which is really the Maned Rat (Lophiomys imhausi), although not nearly as marketable under that name. Others are the mouse-like hamsters (Calomyscus spp.), and the white-tailed rat (Mystromys albicaudatus).