Hamster

Hamster Temporal range: Middle Miocene–Recent
Golden Hamster
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Class:	Mammalia
Order:	Rodentia
Suborder:	Myomorpha
Superfamily:	Muroidea
Family:	Cricetidae
Subfamily:	Cricetinae Fischer de Waldheim, 1817
Genera
Mesocricetus Phodopus Cricetus Cricetulus Allocricetulus Cansumys Tscherskia

Hamsters are rodents belonging to the subfamily Cricetinae. The subfamily contains about 25 species, classified in six or seven genera.^[1]

Hamsters are crepuscular animals which burrow underground in the daylight to avoid being caught by predators. Their diet includes a variety of foods, including dried food, berries, nuts, fresh fruits and vegetables. In the wild they feed primarily on seeds, fruits and greens, and will occasionally eat burrowing insects.^[2] They have an elongated pouch on each side of their heads that extend to their shoulders, which they stuff full of food to be stored, brought back to the colony or to be eaten later.

Although the Golden Hamster (Mesocricetus auratus) was first described scientifically in 1839, it was not until 1930 that researchers were able to successfully breed and domesticate hamsters.^[3] Pet Golden Hamsters are descended from hamsters first found and captured in Syria by zoologist Israel Aharoni.^[4]

Hamster behavior can vary depending on their environment, genetics, and interaction with people. Because they are easy to breed in captivity, hamsters are often used as lab animals in more economically developed countries. Hamsters have also become established as popular small house pets.^[3] Hamsters are sometimes accepted even in areas where other rodents are disliked, and their stereotypically solitary nature can reduce the risk of excessive litters developing in households.

Etymology of name

The name hamster derives from the German Hamster, which itself comes from earlier Old High German hamustro. Possibly related to Old Russian choměstrǔ, which is either a blend of the root of Russian khomiak "hamster" and a Baltic word (cf. Lithuanian staras "hamster")^[5] or of Persian origin (cf. Av hamaēstar "oppressor")^[6]

Characteristics

Hamsters are stout-bodied, with tails shorter than body length, and have small furry ears, short stocky legs, and wide feet. Their thick, silky fur, which can be long or short, can be black, gray, honey, white, brown, yellow, or red depending on the species, or a mix of any of those colors.

Roborovski hamster

Two species of hamsters belonging to the genus Phodopus (Phodopus campbelli, Campbell's Dwarf Hamster, and Phodopus sungorus, the Djungarian Hamster) and also two of the species of the genus Cricetulus, (Cricetulus barabensis, the Chinese Striped Hamster, and Cricetulus griseus, the Chinese Dwarf Hamster) have a dark stripe down the head to tail. The species of genus Phodopus are the smallest, with bodies 5.5 to 10.5 centimetres (2.2 to 4.1 in) long; the largest is the European Hamster (Cricetus cricetus), measuring up to 34 centimetres (13.4 in) long, not including a short tail of up to 6 centimetres (2.4 in). The Angora hamster, also known as the long-haired or Teddy Bear hamster, which is a type of the Golden Hamster is the second-largest hamster breed, measuring up to 18 centimetres (7.1 in) long.^[3]

Hamsters have poor eyesight; they are nearsighted and colorblind. "To compensate for their poor sight when in unfamiliar territory, hamsters have scent glands on their flanks (and abdomens in Chinese and dwarf hamsters). A hamster rubs these areas of his body against various objects, and leaves a trail of smells the hamster can follow to return to his home den." Hamsters can use their sense of smell to detect gender, locate food, and detect pheremones. They are also particularly sensitive to high-pitched noises and can hear and communicate in the ultrasonic range.^[4]

The tail is sometimes difficult to see; usually it is not very long (about 1/6 the length of their body) with exception of the Chinese dwarf hamster whose tail is the same length as the body. On a long haired hamster it is barely visible. Hamsters are very flexible, and their bones are somewhat fragile. They are extremely susceptible to rapid temperature changes and drafts, as well as extreme heat or cold.

Hamsters are omnivorous. They eat most things, and although they should regularly be given a diet of normal hamster food, it is enjoyable for both the owner and the hamster to experiment with other things, such as vegetables, fruits (though these should be removed once they go rotten or bad), seeds, and nuts. Hamsters are hindgut fermenters and must eat their own feces in order to digest their food a second time. This practice is called coprophagy and is necessary for the hamster to obtain the proper nutrients from its food.^[1]

One characteristic of rodents that is highly visible in hamsters is their sharp incisors. They have two pairs in the front of their mouths and these incisors never stop growing and thus must be regularly worn down. Hamsters carry food in their spacious cheek pouches to their underground storage chambers. When full, their cheeks can make their heads double (or even triple) in size.^[1] Hamsters in the Middle East have been known to hunt in packs to find insects for food.^[7]

Behavior

Syrian hamster grooming

Syrian Hamsters (Mesocricetus auratus) are generally solitary and may fight to the death if put together. Some dwarf hamster species may get along with others of the same species. Russian hamsters form close, monogamous bonds with their mates. If separated, they may become very depressed. This happens especially in males. Males will become inactive, eat more, and even show some behavioural changes similar to some types of depression in humans. This can even cause obesity in the hamster.

Hamsters are primarily considered crepuscular because they live underground during most of the day, only leaving their burrows about an hour before sundown and then returning when it gets dark. At one point they were considered nocturnal because they may get up during the night. Some species have been observed to show more nocturnal activity than others, but primarily they are all crepuscular.^[4] All hamsters are excellent diggers, constructing burrows with one or more entrances and with galleries that are connected to chambers for nesting, food storage, and other activities.^[1] They will also appropriate tunnels made by other mammals; the Djungarian Hamster (Phodopus sungorus), for instance, uses paths and burrows of the pika. Although hamsters do not hibernate per se, they do “close down” a number of systems, such as breathing and heartbeat rate, for short periods of time. These periods of torpor, which is "a state of mental or physical inactivity or insensibility" can last up to seven to ten days.^[8] "A hibernating hamster will curl up into a ball in the nest to conserve as much heat as possible in the abdominal region. You will be able to pick the hamster up without him knowing it, and he will not wake up on handling. But close observation will reveal the hamster’s whiskers (vibrissae) are still twitching. The hamster still has to breathe when in torpor, although very very slowly this will be seen on close observation. The hamster must be aroused by slowly warming and gentle handling and stroking. After the arousal period it may be noted that hamster may be little groggy and trembling this will last only for a very short time."

Reproduction

A mother Syrian hamster with pups under one week old.

Hamsters become fertile at different ages depending on their species, but this can be from one month to three months of age. The female’s reproductive life only lasts about 18 months, but male hamsters remain fertile much longer. Females are in heat approximately every four days, which is indicated by a reddening of genital areas, a musky smell and a hissing, squeaking type noise she will give off if she believes a male is nearby.^[3]

Hamsters are seasonal breeders. Breeding season is from April to October in the northern hemisphere, with two to five litters of 1 to 13 young being born after a gestation period of 16 to 23 days.^[7] Gestation lasts 16 to 18 days for Golden Hamsters, 18 to 21 days for the Russian hamsters, 21 to 23 days for Chinese hamsters and 23 to 30 for Roborovski Hamsters. The average litter for Golden Hamsters 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 to 8 in a litter but can have up to 14. Djungarian Hamsters tend to have slightly smaller litters, as do Chinese and Roborovski hamsters.

Chinese hamster females are known for being aggressive toward the male if kept together for too long. In some cases, male Chinese hamsters can die after being attacked by the female. If breeding Chinese hamsters, it is recommended to separate the pair after mating or the hamsters will attack each other.

Syrian hamster females are also very aggressive toward male hamsters and must be separated immediately after breeding in order to prevent an attack. Female hamsters are also particularly sensitive to disturbances while giving birth and may even eat her own young if she thinks they are in danger, although sometimes she is just carrying the pups in her cheek pouches.^[4]

Hamsters are born hairless and blind in a nest that the mother will have prepared in advance.^[3] After one week they begin to explore outside the nest. They are completely weaned after three weeks, or four for Roborovski Hamsters. Most breeders will sell the hamsters to shops when the hamsters are anywhere from three to nine weeks old.

Mating 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 Djungarian) live approximately 2 to 4 years in captivity, and Chinese Hamsters 2.5 to 3 years. The smaller Roborovski Hamster often lives to 2–3 years in captivity.^[1] Both Golden 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. When seen from above, a sexually mature female hamster has a trim tail line; a male's tail line bulges on both sides. This might not be very visible in all species. 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 their anal and genital openings close together, whereas males have these two holes farther apart (the penis is usually withdrawn into the coat and thus appears as a hole or pink pimple).^[3]

It should also be noted that if a captive hamster is left for extended periods (3–4 weeks and more) with her litter, there is a high possibility that she will cannibalize the litter. It is therefore imperative that the litter be split up by the time the young can collect their own food and water.

Hamsters as pets

A Sable short-haired Golden Hamster

The best-known species of hamster is the Golden or Syrian 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. British zoologist Leonard Goodwin claimed that most hamsters kept in the United Kingdom were descended from the colony he introduced for medical research purposes during the Second World War.^[9]

A Russian dwarf hamster

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 Djungarian or Winter-white Russian Dwarf Hamster (Phodopus sungorus) turns almost white during winter (when the hours of daylight decrease).^[3] The Roborovski Hamster (Phodopus roborovskii) is extremely small and fast, making it difficult to keep as a pet.^[1] 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 are of vital importance when planning the breeding. 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.^{[citation needed]}

Classification

Taxonomists generally 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. Their evolutionary history is recorded by 15 extinct fossil genera and extends back 11.2 million to 16.4 million years to the Middle Miocene Epoch in Europe and North Africa; in Asia it extends 6 million to 11 million years. Four of the seven living genera include extinct species. One extinct hamster of Cricetus, for example, lived in North Africa during the Middle Miocene, but the only extant member of that genus is the European or Common Hamster of Eurasia.

• Subfamily Cricetinae
  • Genus Allocricetulus
    • Species A. curtatus—Mongolian Hamster
    • Species A. eversmanni—Eversmann's or Kazakh Hamster
  • Genus Cansumys
    • Species C. canus—Gansu Hamster
  • Genus Cricetulus
    • Species C. alticola—Tibetan Dwarf or 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 (Dwarf) Hamster, also called Rat Hamster
    • Species C. kamensis—Kam Dwarf Hamster or Tibetan Hamster
    • Species C. longicaudatus—Long-tailed Dwarf Hamster
    • Species C. migratorius—Gray Dwarf Hamster, Armenian Hamster, Migratory Grey Hamster; Grey Hamster; Migratory Hamster
    • Species C. sokolovi—Sokolov's Dwarf Hamster
  • Genus Cricetus
    • Species C. cricetus—European Hamster, also called Common Hamster or Black-Bellied Field Hamster
  • Genus Mesocricetus—Golden Hamsters
    • Species M. auratus—Golden or Syrian 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 Dwarf Hamster
    • Species P. roborovskii—Roborovski Hamster
    • Species P. sungorus—Djungarian Hamster or Winter-white Russian Dwarf Hamster
  • Genus Tscherskia
    • Species T. triton—Greater Long-tailed Hamster, also called Korean Hamster

Relationships among hamster species

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 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.

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.

Miscellaneous

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

Similar animals

Note that there are some rodents that 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).

See also

• Chinchilla
• Gerbil
• Guinea pig
• Hampster Dance
• Hamster racing
• Hamtaro
• Rat
• Tales of the Riverbank

References

Notes

1. ^ ^{a b c d e f} Fox, Sue. 2006. Hamsters. T.F.H. Publications Inc.
2. ^ Patricia Pope Bartlett ([2003). The Hamster Handbook. Barron's Educational Series. p. 113. ISBN 9780764122941. http://books.google.com/books?id=QVlYZiNiSckC. 
3. ^ ^{a b c d e f g} Barrie, Anmarie. 1995. Hamsters as a New Pet. T.F.H. Publications Inc., NJ.
4. ^ ^{a b c d} Fritzsche, Peter. 2008. Hamsters: A Complete Pet Owner’s Manual. Barron’s Educational Series Inc., NY.
5. ^ Douglas Harper, The Online Etymology Dictionary, entry for "hamster"
6. ^ Merriam-Webster's Collegiate Dictionary, s.v. "hamster" (May 29, 2008) Merriam-Webster.com
7. ^ ^{a b} "hamster." Encyclopædia Britannica. Standard Edition. Chicago: Encyclopædia Britannica, 2007.
8. ^ http://www.thefreedictionary.com/torpor
9. ^ "Leonard Goodwin - Telegraph". The Daily Telegraph. 14 January 2009. http://www.telegraph.co.uk/news/obituaries/4241645/Leonard-Goodwin.html. Retrieved 2009-01-18. 

Bibliography

• 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.

External links

• National Hamster Council (UK)