Hamster
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| Hamsters Temporal range: Middle Miocene - Recent
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| Campbell's Dwarf Hamster | |
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| Subfamily: | Cricetinae Fischer de Waldheim, 1817
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Mesocricetus | |
A hamster is a rodent belonging to the subfamily Cricetinae. The subfamily contains about 18 species, classified in six or seven genera. Hamsters are indigenous to the Middle East and southeastern Europe. Because they are easy to keep and breed in captivity, hamsters are often used as lab animals and pets.
Hamsters as pets
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," and "Dalmatian," depending on their coloration. There are also several variations, including long-haired ones that grow hair several centimeters long and often require special care.
Other hamsters that are kept as pets are four species of dwarf hamster. Campbell's Hamster (Phodopus campbelli) is the most common of the four—they are also sometimes called "Russian Dwarfs"; however, many hamsters originate in Russia, and so this name does not distinguish them. The coat of the Winter White 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 4 cm 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 is 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 well cared for and handled regularly and so make very suitable pets. Buying a hamster direct from the breeders means that there is the opportunity to see the parents and know the date of birth of the hamster(s) that it is intended to purchase.
Housing
Hamsters can be kept both in cages and in terrariums, 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 housings 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 bigger housings than their larger relatives, at least 80 cm by 40 cm (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 for 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 heating.
The floors of a hamster's residence is generally covered with a layer of litter. Litters made from recycled paper or woods 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 are also commercial beddings, such as Carefresh and Megazorb.
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An often-used type of hamster cage with tubes
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Hamster cage with wheel and water bottle -
Note that these standard tubes cannot be used at a steep incline with dwarf hamsters.
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 hamster's enclosures. 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.
Hamsters are nest builders, so most owners supply strips of tissue or newspaper so they may build a secure spot in a corner or in their "house." 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. Hamsters, like many rodents, are also extensive gnawers, and must be supplied with appropriate materials for doing so.
Food
Many hamsters tend to carry away food from their food 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, may be most dangerous for the hamster's health. There are many myths regarding unsafe foods including that feeding lettuce causes wet tail and citrus fruits being toxic - both of which are untrue. Lettuce however has very little nutritional value and in excess can cause liver problems, and some hamsters may not like the taste of citrus fruits but they are safe to feed hamsters have been observed in orange groves in the wild [citation needed]. Campbells dwarf hamsters are susceptible to hereditary diabetes, and any hamster suffering from diabetes should not have high sugar foods, such as fruits 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.
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 babies 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, young hamsters are harder to sex. When examined, female hamsters have two holes close together whereas males have anal and genital openings further apart than the female's (the member is usually withdrawn into the coat and thus appears as a hole or pink pimple).
After a female hamster mates, there is a gestation period of 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 womb. Campbell's Russian hamsters tend to have 4-8 in a litter but can have up to 14, Winter White Russian hamsters tend to have slightly smaller litters, as do the Chinese and Roborovski hamsters.
Mother hamster gathers all the pups into a nest which it built. They are hairless, have closed eyes, nurse from their mother, and move very little. After about a week, they begin to wander from the nest and eat solid food. After a total of three weeks, the pups are weaned and can leave the nest for good, save for Roborovski hamsters that mature at a slower rate and should not be removed from the mother until 4 weeks of age.
Health concerns
Teeth 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 dropped 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.[1]
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 immediately examined by a veterinarian to determine the best course of action in each situation.[1]
Bladder stones
Hamsters are susceptible to formation of bladder stones. Although the owner usually will typically not detect the stone, symptoms include frequent and painful urination, blood in the urine, increased water consumption, and loss of appetite. Only a veterinarian can remove the stone and provide appropriate antibiotics.[1]
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 in size, so the owners typically elect not to operate, but, rather, elect to euthanize the pet.[1]
Neglect
A common problem for hamsters is neglect, which can cause the hamsters to not get adequate food and water, causing serious health concerns, including serious dehydration, starvation, stomach ulcers, eating of bedding material, and cannibalism. It is important to regularly check water bottles, as they often become clogged or contact bedding, draining the bottles.[1]
Abscesses
Abscesses, caused by either bite wounds from fighting or by harsh food or bedding, are likely to become infected, forming abscesses that appear as firm, painful lumps under the skin. If an abscess is detected or suspected, it must be drained or removed by a veterinarian before prescribing antibiotics.[1]
Wet tail
The most serious intestinal disease of hamsters is "wet tail", or Proliferative Ileitis, which is most common among weening hamsters (3-6 weeks) and Teddy Bear 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.[1]
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 fruits and vegetables, which can be avoided by thoroughly washing them before they are offered to hamsters. Treatment includes either antibiotics or euthanasia.[1]
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 it's highly unlikely as hamsters are indoor pets. Lymphocytic choriomeningitis is transmittable to humans, which signs such as recurrent fever, headache, fatigue, muscle aches, sore throat, rash, and arthritis.[1]
Demodectic mange
Demodectic mange, 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.[1]
Intestinal parasites
Hamsters frequently harbor intestinal parasites within their small intestines:
- Tapeworm is the most common and 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 must submit a fecal sample to a veterinarian for diagnosis. If there are eggs in the sample, treatment can be instituted by the veterinarian.[1]
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 the eyeless whites is also shortened to around 9-12 months.
Blind hamsters 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.[2]
Classification of hamsters
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 Mesocricetus - Golden hamsters
- Syrian hamster (Mesocricetus auratus); also called the Golden hamster or Teddy Bear hamster.
- Turkish hamster (Mesocricetus brandti); also called Brandt's hamster, Azerbajaini hamster
- Georgian Hamster (Mesocricetus raddei); also Ciscaucasian Hamster
- Romanian Hamster (Mesocricetus newtoni)
- Genus Phodopus - Dwarf hamsters
- Winter White Russian Dwarf Hamster (Phodopus sungorus)
- Campbell's Russian Dwarf Hamster (Phodopus campbelli)
- Roborovski Hamster (Phodopus roborovski); sometimes known as the Mongolian Hamster, although this causes confusion with Allocricetulus curtatus
- Genus Cricetus
- European Hamster (Cricetus cricetus); also called the Common Hamster or Black-bellied Field Hamster
- Genus Cricetulus
- Ladak Hamster (Cricetulus alticola)
- Striped Dwarf Hamster (Cricetulus barabensis including "C. pseudogriseus" and "C. obscurus"); also Chinese striped hamster, Chinese hamster
- Chinese Hamster (Cricetulus griseus)
- Tibetan Hamster (Cricetulus kamensis)
- Long-tailed Hamster (Cricetulus longicaudatus)
- Armenian Hamster (Cricetulus migratorius); also called the Migratory Grey Hamster, Grey Hamster, Grey Dwarf Hamster, or Migratory Hamster
- Sokolov's Hamster (Cricetulus sokolovi)
- Genus Allocricetulus
- Mongolian Hamster (Allocricetulus curtatus)
- Kazakh Hamster (Allocricetulus eversmanni); also Eversmann's Hamster
- Genus Cansumys
- Gansu Hamster (Cansumys canus)
- Genus Tscherskia
- Greater Long-tailed Hamster (Tscherskia triton); also Korean Hamster
- Genus Mesocricetus - Golden hamsters
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:
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.
Mesocricetus group
The genus Mesocricetus also formed a clade. Their analysis included all four species, with M. auratus and M. raddei forming one subclade and M. brandti and M. newtoni another.
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.
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).
References
- Lebedev, V. S., N. V. Ivanova, N. K. Pavlova, and A. B. Poltoraus. 2003. Molecular phylogeny of the Palearctic hamsters. In Proceedings of the International Conference Devoted to the 90th Anniversary of Prof. I. M. Gromov on Systematics, Phylogeny and Paleontology of Small Mammals (A. Averianov and N. Abramson eds.). St. Petersburg.
- Musser, G. G. and M. D. Carleton. 2005. Superfamily Muroidea. In Mammal Species of the World a Taxonomic and Geographic Reference (D. E. Wilson and D. M. Reeder eds.). Johns Hopkins University Press, Baltimore.
- Neumann, K., J. Michaux, V. Lebedev, N. Yigit, E. Colak, N. Ivanova, A. Poltoraus, A. Surov, G. Markov, S. Maak, S. Neumann, R. Gattermann. 2006. Molecular phylogeny of the Cricetinae subfamily based on the mitochondrial cytochrome b and 12S rRNA genes and the nuclear vWF gene. Molecular Phylogenetics and Evolution, in press; Available online 17 February 2006.
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