Hamster


Hamsters are rodents belonging to the subfamily Cricetinae, which contains 19 species classified in seven genera. They have become established as popular small pets. The best-known species of hamster is the golden or Syrian hamster, which is the type most commonly kept as a pet. Other hamster species commonly kept as pets are the three species of dwarf hamster, Campbell's dwarf hamster, the winter white dwarf hamster and the Roborovski hamster, and the less common Chinese hamster.
Hamsters feed primarily on seeds, fruits, vegetation, and occasionally burrowing insects. In the wild, they are crepuscular: they forage during the twilight hours. In captivity, however, they are known to live a conventionally nocturnal lifestyle, waking around sundown to feed and exercise. 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

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 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

Neumann et al. 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:

''Phodopus'' group

The genus Phodopus was found to represent the earliest split among hamsters. Their analysis included both species. The results of another study suggest Urocricetus kamensis and the related U. alticola belong to either this Phodopus group or hold a similar basal position.

''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 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 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 hamastra. It is possibly related to Old Church Slavonic khomestoru, which is either a blend of the root of Russian хомяк "hamster" and a Baltic word ; or of Persian origin. The collective noun for a group of hamsters is "horde". In German, the verb hamstern is derived from Hamster. It means "to hoard".

Description

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 and the Djungarian hamster, and two of the genus Cricetulus, the Chinese striped hamster and the Chinese hamster 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, 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, 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 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 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. They are also particularly sensitive to high-pitched noises and can hear and communicate in the ultrasonic range.

Diet

Hamsters are omnivores, which means they can eat meat and plant matter. Hamsters that live in the wild eat seeds, grass, and even insects. Although pet hamsters can survive on a diet of exclusively commercial hamster food, other items, such as vegetables, fruits, seeds, and nuts, can be given. Although store-bought food is good for hamsters, it is best if fruits and vegetables are also in their diet because it keeps them healthier. 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 to recover nutrients digested in the hind-gut, but not absorbed.

Behavior

Feeding

A behavioral characteristic of hamsters is food hoarding. They carry food in their spacious cheek pouches to their underground storage chambers. When full, the cheeks can make their heads double, or even triple in size. Hamsters lose weight during the autumn months in anticipation of winter. This occurs even when hamsters are kept as pets and is related to an increase in exercise.