Cricetus cricetus (Linnaeus, 1758), Germany. OTHER COMMON NAMES
English: Common hamster, European hamster, field hamster. PHYSICAL CHARACTERISTICS
The largest hamster, 8-12 in (20-34 cm) long; males larger than females (10.5-12.5 in [27-32 cm] versus 8.7-9.8 in [22-25 cm]). Tail short and hairless, 1.6-2.4 in (40-60 mm). Weight 4.5-36.3 oz (112-908 g), averaging 18 oz (450 g) for males and 14 oz (350 g) for females. Thick fur is reddish brown above with white patches on the flanks, nose, cheeks, and throat, and black underparts—unusual in mammals. Color variations, from albino to melanistic, are common.
Black-bellied hamsters live in lowlands of central and Eastern Europe, from Belgium to the Altai region of Siberia.
Throughout much of their range, the hamsters' natural steppe habitat has been converted to agricultural land; they have adapted to living in and along farm fields, especially where both grain and root crops are grown. Occasionally, they dig burrows along riverbanks. These hamsters generally prefer low elevation habitat but can found up to an altitude of 2,000 ft (610 m).
When suitable burrowing sites are in short supply, black-bellied hamsters may burrow quite close together; however
these clusters are not true colonies; like most hamsters, members of this species are solitary in their habits. They are also active nocturnally and hibernate in winter. Winter burrows can be very deep, extending more than 6 ft (2 m) below the soil surface. Cricetus burrows are particularly complex, with several entrance tunnels, numerous chambers for nesting and food storage, and a dead-end tunnel used as a toilet area. The size of the burrow is correlated with the hamster's age; old females with young have the most complex burrows.
Black-bellied hamsters live in regions that can be quite cold in winter; they hibernate but wake up every 5-7 days to feed on their stored supplies. The length of hibernation is influenced by weather and other factors but typically occurs from the end of September through April.
When the hamster population in a given area reach a very high density, some members of the population become restless and leave, spreading out into new locations. Capable of swimming, the hamsters sometimes cross large rivers during these wanderings.
As with most hamsters the diet includes grains, beans, roots, and the green parts of plants; black-bellied hamsters also eat insect larvae—especially beetle larvae—frogs, earthworms, and field mice. They often store very large quantities of cereal grains, seeds, peas and potatoes in their winter burrows; there are reports of burrows containing as much as 198 lb (90 kg) of food.
Most breeding activity takes place between June and August, although breeding can begin earlier or continue later, depending on location and climate. Probably serially monogomous. A courting male will enter the female's territory and mark the area with secretions from glands in his flanks. A lengthy courtship ritual ensues, in which the male runs after the female, making a loud sniffing noise that serves as his mating call. After mating occurs, the female becomes aggressive and drives the male away. (In captivity, however, male black-bellied hamsters sometimes help to raise the young.)
The female cushions the floor of the nest chamber with grass stalks. The gestation period is 18-20 days. A typical litter is 4-12 pups; the female has eight nipples and usually raise no more than eight young. Newborns weigh about 0.2 oz (7 g). They start to eat solid food at one week, when their eyes are still closed; at age two weeks they open their eyes and have acquired a full coat of fur. At three weeks they are weaned; they will reach adult size at eight weeks. A female typically has two litters per year in the wild. These are comparatively long-lived hamsters, sometimes reaching the age of eight years old.
Sometimes considered a serious pest on farms, black-bellied hamsters in the twentieth century were often systematically poisoned with rodenticides. This practice, combined with habitat loss, due both to changes in farming practices and spreading industrial construction, has led serious population declines in some locations. As of 2000, this hamster was protected under the European Community Habitats Directive as a threatened species in Germany, Belgium, the Netherlands, France, and Austria. They are also protected in Bulgaria, Croatia, and Slovenia, where they are uncommon, not because of human actions, but because they are at the edge of their range.
As land was increasingly cleared for farming in the Middle Ages, this probably created conditions favorable for hamsters and led to a rise in populations. Historically this species has been widely hunted for food and trapped for its colorful fur, which was used to make clothing or as a warm lining; as of 2001 hamsters were still being trapped in eastern European nations where they are common, such as Hungary, and the fur was still being used in some high-fashion garments.
Black-bellied hamsters have historically been a particular pest in corn fields; corn is often the last crop to be harvested, so hamsters from neighboring fields congregate in corn fields after their other food sources are gone. It's worth noting that this species can also be helpful to farmers because it hunts field mice and insect pests.
Finally, the black-bellied hamster is sometimes used as a lab animal, particularly in oncology research. ♦
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