Etymology of nameThe 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") or of Persian origin (cf. Av hamaēstar "oppressor")
 CharacteristicsHamsters 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.
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.
Hamsters have poor eyesight; they are nearsighted and colorblind. However, they have an acute sense of smell and can hear extremely well. 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.
The tail is sometimes difficult to see; usually it is not very long (about 1/6th 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 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.
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.
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. Hamsters in the Middle East have been known to hunt in packs to find insects for food.
 BehaviorSiberian 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 are active all night. Some species have been observed to be more nocturnal than others. 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. 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 can last up to seven to ten days. Hamsters are known to stockpile large amounts of food where they sleep, making it possible to leave pet hamsters alone for a few days without food.
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. 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.
Golden 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.
Hamsters are born hairless and blind in a nest that the mother will have prepared in advance. 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 longevityGolden 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 1.5 to 2 years in captivity, and Chinese Hamsters 2.5 to 3 years. The smaller Roborovski Hamster often lives to 2–3 years in captivity. 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).
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 petsGolden 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.
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). The Roborovski Hamster (Phodopus roborovskii) is extremely small and fast, making it difficult to keep as a pet. 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. 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.