The name hamster is derived from the German word Hamster, itself from earlier OHG hamustro, from ORuss choměstorǔ, which is either a blend of the root of Russ khomiak "hamster" and a Baltic word (cf. Lith staras "hamster") or of Iranian origin (cf. Av hamaēstar "oppressor").
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. Recently hamsters have also become established as popular small family pets.
Hamsters are crepuscular. In the wild, they burrow underground in the daylight to avoid being caught by predators. They are most active around dusk and dawn, which has led many people to mistake them for being nocturnal. Their diet contains a variety of foods, including dried food, berries, nuts, fresh fruits and vegetables. In the wild they will eat any wheat, nuts and small bits of fruit and vegetables that they might find lying around on the ground, and will occasionally eat small insects such as small crickets or mealworms. They have elongated fur-lined pouches on both sides of their heads which extend to their shoulders, which they stuff full of food to be brought back to the colony or to be eaten later.
Pet stores sell a variety of treats that are suitable for hamsters. However, it is important not to give a hamster too many of these, especially ones that are high in fat or sugar, because they may lead to the hamster getting diabetes. It is better to give hamsters fresh vegetables over fresh fruit, as fruit is also high in sugar. If you give hamsters fruit it is always best to do so as a treat and in extremely small amounts. The skin of fruits such as apples and pears is also good. It is also important not to give a hamster too much fresh fruit, as they can cause diarrhea.
Occasionally, people try to feed their hamster everyday foods found in their kitchen. It is best to avoid human foods that will make them unhealthy or be hard for them to digest. Any fruits or vegetables should be chosen carefully. It is also important to thoroughly wash fruits, vegetables and greens before feeding, as they can have traces of pesticides. Some foods to avoid giving hamsters are kidney beans, onion, garlic, large amounts of citrus fruit, and potato sprouts. Some hamsters also shouldn't eat iceberg lettuce, as it causes diarrhea and is poisonous to some hamsters . Dark leafy greens are preferred, such as kale and spinach. Celery, green beans, carrots, broccoli on occasion are great also.
Breeding season is from April to October, 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 Syrian 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 Syrians 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. Winter White Russian Dwarf Hamsters tend to have slightly smaller litters, as do Chinese and Roborovski hamsters.
Siberian 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 behavioral changes similar to some types of depression in humans. This can even cause obesity in the hamster.
Chinese hamster females are known for being aggressive toward the male if kept together for too long. In some cases, male Chinese hamsters have died 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.
Hamsters are born hairless and blind in a nest which the mother will have prepared in advance. She uses shredded material such as leaves in the wild but prefers cotton or toilet paper in captivity. 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 two to eight weeks old.
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," "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.
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 Winter White Russian Dwarf 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 4cm 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.
In Australia it is illegal to keep hamsters as pets as 'escapees' could breed in the wild and become 'feral' pest animals.
Despite the hamster’s small size, appropriate housing 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 more spacious housing than their larger relatives, at least 80cm by 40cm (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 to 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 overheating. Dwarf hamsters like it a bit cooler.
The floor of a hamster's residence is generally covered with a layer of litter. The best products for in cage bedding are pine or aspen wood shavings. There are also paper pulp based products available, as well as a variety of recycled products, though newspaper products may contain inks, dyes and other chemicals from the paper making process. There is some controversy over whether they should be be given cedar shavings, as the oils in the wood are particularly aromatic and could cause problems in mice with respiratory sensitivities. If odor is a serious concern, kiln dried pine bedding is probably best, as the natural properties of the wood control odor and absorb ammonia. Recent research suggests that paper pulp beddings may allow very high concentrations of ammonia to build up in cages, especially those with little ventilation.
Hamsters are nest builders, so some owners supply twigs, leaves and wood bits so that they can build a secure spot in a corner or in their "house". Avoid using newspapers as the ink on it might be ingested when the hamster chews on them. Also avoid bleached-white toilet paper. Supplying strips of toilet paper can lead to stomach blockage and death after accidental ingestion by some hamsters. 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. Therefore, select dry hay such as Timothy and use the softer, leafy parts of the hay rather than the stems. It is not advisable to use lint, as the hamster may consume it and the lint will block their intestinal passage. Fine chinchilla sand (not chinchilla dust because the powdery material will cause respiratory problems) can be given in an enclosed container. Hamsters enjoy rolling in the sand to keep their fur clean and dry.
Hamsters, like many rodents, are also gnawers, and must be supplied with appropriate materials for doing so; for example, an edible gnaw toy or an unpainted wooden block can be placed in the cage. Failure to do so can cause dental problems for the hamster, as the incisors, which grow continually, will become too long and cause discomfort and/or eating problems.
Many hamsters tend to carry food from the 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, are dangerous for hamsters. Citrus fruits such as oranges and lemons should never be fed to a hamster because their stomachs can not handle the acid. Iceburg lettuce has very little nutritional value and in excess can cause liver problems. Campbell's Dwarf Hamsters are susceptible to hereditary diabetes, and any hamster suffering from diabetes should not have high sugar foods, such as fruit 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.
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 pups 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, it is more difficult to determine a young hamster's sex. When examined, female hamsters have two holes close together, whereas males have anal and genital openings further apart than the female's. (The penis is usually withdrawn into the coat and thus appears as a hole or pink pimple.)