Hamster - WikiHQ

Hamsters are rodents (order Rodentia) belonging to the subfamily Cricetinae, which contains 19 species classified in seven genera. They have become established as popular small pets. Physically, they are stout-bodied with distinguishing features that include elongated cheek pouches extending to their shoulders, which they use to carry food back to their burrows, as well as a short tail and fur-covered feet.

Classification

thumb|right|P. sungorus. The [[winter white dwarf hamster]]

thumb|A winter white dwarf hamster

thumb|right|P. roborovski. The [[Roborovski hamster]]

thumb|right|P. campbelli. The [[Campbell's dwarf hamster]]

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. 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, sometimes considered a synonym of C. barabensis
Species C. longicaudatus—long-tailed dwarf 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 Nothocricetulus - grey dwarf hamster
Species N. migratorius—grey dwarf hamster, Armenian hamster, migratory grey hamster; grey hamster; migratory 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
Genus Urocricetus
Species U. alticola - Ladakh dwarf hamster
Species U. kamensis - Kam dwarf hamster

Relationships among hamster species

thumb|right|Hamster clades

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

Mesocricetus group

The genus Mesocricetus also forms 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 C. barabensis (and presumably the related C. sokolovi) and C. longicaudatus.

Miscellaneous

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

History

Although the Syrian hamster or golden hamster (Mesocricetus auratus) was first described scientifically by George Robert Waterhouse in 1839, researchers were not able to successfully breed and domesticate hamsters until 1939. The entire laboratory and pet populations of Syrian hamsters appear to be descendants of a single brother–sister pairing. These littermates were captured and imported in 1930 from Aleppo in Syria by Israel Aharoni, a zoologist of the University of Jerusalem. In Jerusalem, the hamsters bred very successfully. Years later, animals of this original breeding colony were exported to the United States, where Syrian hamsters became a common pet and laboratory animal. Comparative studies of domestic and wild Syrian hamsters have shown reduced genetic variability in the domestic strain. However, the differences in behavioral, chronobiological, morphometrical, hematological, and biochemical parameters are relatively small and fall into the expected range of interstrain variations in other laboratory animals.

Etymology

The name "hamster" is a loanword from the German, which itself derives from earlier Middle High German . It is possibly related to Old Church Slavonic , which is either a blend of the root of Russian () "hamster" and a Baltic word (cf. "hamster"); or of Persian origin (cf. Avestan: "oppressor"). The collective noun for a group of hamsters is "horde". In German, the verb is derived from . It means "to hoard".

Description

right|thumb|Skeleton of [[European hamster]]

Hamsters are typically stout-bodied, with tails shorter than body length, and have small, furry ears, short, stocky legs, and wide feet. They have thick, silky fur, which can be long or short, colored black, grey, honey, white, brown, yellow, red, or a mix, depending on the species. Two species of hamster belonging to the genus Phodopus, Campbell's dwarf hamster (P. campbelli) and the Djungarian hamster (P. sungorus), and two of the genus Cricetulus, the Chinese striped hamster (C. barabensis) and the Chinese hamster (C. griseus) have a dark stripe down their heads to their tails. The species of genus Phodopus are the smallest, with bodies long; the largest is the European hamster (Cricetus cricetus), measuring up to long, not including a short tail of up to .

The hamster tail can be difficult to see, as it is usually not very long (about the length of the body), with the exception of the Chinese hamster, which has a tail the same length as the body. One rodent characteristic that can be highly visible in hamsters is their sharp incisors; they have an upper pair and lower pair which grow continuously throughout life, so must be regularly worn down. Hamsters are very flexible, but their bones are somewhat fragile. They are extremely susceptible to rapid temperature changes and drafts, as well as extreme heat or cold.

Senses

Hamsters have poor eyesight; they are nearsighted and colorblind. Their eyesight leads to them not having a good sense of distance or knowing where they are, but that does not stop them from climbing in (and sometimes out of) their cages or from being adventurous. Hamsters can sense movement around at all times, which helps protect them from harm in the wild. In a household, this sense helps them know when their owner is near. Hamsters have scent glands on their flanks (and abdomens in Chinese and dwarf hamsters) which they rub against the surface beneath them, leaving a scent trail. Hamsters also use their sense of smell to distinguish between the sexes and to locate food. Mother hamsters can also use their sense of smell to find their own babies and identify which ones are not theirs. Their scent glands can also be used to mark their territories, their babies, or their mate. Hamsters catch sounds by having their ears upright. They tend to learn similar noises and begin to know the sound of their food and even their owner's voice. Hamsters in the Middle East have been known to hunt in packs to find insects for food. Hamsters are hindgut fermenters and often eat their own feces (coprophagy) to recover nutrients digested in the hind-gut, but not absorbed.

thumb|right|Hamsters fighting

Most hamsters are strictly solitary. If housed together, acute and chronic stress might occur, When kept as house pets the Syrian hamster does not hibernate. A burrow includes a steep entrance pipe ( in diameter), a nesting and a hoarding chamber and a blind-ending branch for urination. Laboratory hamsters have not lost their ability to dig burrows; in fact, they will do this with great vigor and skill if they are provided with the appropriate substrate.

Reproduction

Fertility

thumb|right|A mother Syrian hamster with pups less than one week old

Hamsters become fertile at different ages depending on their species. 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 two to three months of age, and Roborovskis at three to four months of age. The female's reproductive life lasts about 18 months, but male hamsters remain fertile much longer. Females are in estrus about every four days, which is indicated by a reddening of genital areas, a musky smell, and a hissing, squeaking vocalisation she will emit if she believes a male is nearby.

Longevity

Syrian hamsters typically live no more than two to three years in captivity, and less in the wild. Russian hamsters (Campbell's and Djungarian) live about two to four years in captivity, and Chinese hamsters –3 years. The smaller Roborovski hamster often lives to three years in captivity. Hamsters were domesticated and kept as pets in the United States at least as early as 1942.

thumb|298x298px|A spacious [[hamster cage made from a display cabinet]]

Other hamsters commonly kept as pets are the three species in the genus Phodopus. Campbell's dwarf hamster (Phodopus campbelli) is the most common—they are also sometimes called "Russian dwarfs"; however, many hamsters are from Russia, so this ambiguous name does not distinguish them from other species appropriately. The coat of the winter white dwarf hamster (Phodopus sungorus) turns almost white during winter (when the hours of daylight decrease). Hamster shows are also places where people share their enthusiasm for hamsters among attendees. Hamster shows feature an exhibition of the hamsters participating in the judging.

Hamsters as lab animals

The extracted cells of babies' kidneys and adults' ovaries are used to study cholesterol synthesis.

Similar animals

Some similar rodents sometimes called "hamsters" 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). Others are the mouse-like hamsters (Calomyscus spp.), and the white-tailed rat (Mystromys albicaudatus).

References

External links

National Hamster Council of the UK