Subfamily Cricetinae
hamsters

Cricetines, or hamsters, make up a small Old World subfamily of terrestrial cricetid rodents. There are 18 hamster species in 7 genera. (Musser and Carleton, 2005)

Cricetine rodents have a Palearctic distribution. They are found in central and eastern Europe, in Asia Minor, Syria, and Iran, in Mongolia, Siberia, northern China, and Korea. (Carleton and Musser, 1984)

Cricetines are most common in dry, open habitats. They live in deserts, plains, sand dunes, steppes, shrublands, rocky foothills, river valleys, agricultural fields, gardens, and orchards. Hamsters may be found at elevations up to 3,600 meters. (Carleton and Musser, 1984; Nowak, 1999)

In the past, genera were sometimes placed in Cricetinae that are now classified elsewhere, including sigmodontines (Miller and Gidley 1918), nesomyines (Miller and Gidley 1918, Ellerman 1941), calomyscids (Ellerman 1941), mystromyines (Vorontsov 1966), and myospalacines (Michaux et al. 2001). For the most part, however, Cricetinae is a well-diagnosed, unambiguous monophyletic group, and recent molecular analyses using LCAT and vWF genes (Michaux et al. 2001), IRBP genes (Jansa and Weksler 2004), and GHR, BRCA1, RAG1, and c-myc genes (Steppan et al. 2004) have supported its monophyly. It is unclear which subfamily is the sister group to Cricetinae, and different molecular analyses have suggested that it may be neotomines (Michaux et al. 2001) or arvicolines (Steppan et al. 2004). Steppan et al. (2004) estimated a cricetine-arvicoline divergence date of 16.3 to 18.8 million years ago.

Within Cricetinae, it is unclear how many genera should be recognized. For example, Allocricetulus and Tscherskia are sometimes included in the genus Cricetulus, and Cansumys is sometimes included in Tscherskia (Carleton and Musser 1984). However, as Musser and Carleton (2005) point out, Allocricetulus is actually more similar morphologically to Cricetus than to Cricetulus, and Cricetulus resembles Phodopus more than it does Tscherskia or Allocricetulus. Thus, they advise leaving these genera separate until a comprehensive analysis of cricetine generic relationships is undertaken. (Carleton and Musser, 1984; Ellerman, 1941; Jansa and Weksler, 2004; Michaux, Reyes, and Catzeflis, 2001; Miller and Gidley, 1918; Musser and Carleton, 2005; Steppan, Adkins, and Anderson, 2004; Vorontsov, 1966)

Hamsters are small to large muroid rodents with compact bodies, small, furry ears, short legs, wide feet, and short stubby tails. Body lengths range from 50 mm to 340 mm, and tail lengths range from 7 to 106 mm. Females of some species are larger than males. Hamsters have long, thick fur. They are gray, pinkish buff, light brown, or reddish brown on the dorsal surface and white, gray, or black on the ventral surface. Their flanks are often white as well. Some have a middorsal stripe. Hamsters have large cheek pouches and sebaceous flank glands.

The dental formula of hamsters is 1/1, 0/0, 0/0, 3/3 = 16. The incisors are orthodont and ungrooved, and the molars are rooted and cuspidate. The upper molars have deep labial re-entrant angles, and most cricetines have molars with opposite cusps. The dentary has a pronounced sigmoid notch and coronoid process. The rostrum is long, wide, and robust. The area between the orbits is hourglass shaped, and the zygomatic plate usually lacks a spine or notch. The incisive foramena are usually short. The sphenopalatine vacuities are moderately large. There is a postglenoid foramen, and most have a sphenofrontal foramen and squamosoalisphenoid groove. The bony palate is wide and smooth, and there is usually a single pair of posterior palatine foramina. A strut of the alisphenoid bone separates the masticatory foramen and accessory foramen ovale. Cricentines have vertebral columns with 13 thoracic vertebrae and six lumbar vertebrae.

Hamsters have two-chambered stomachs, and most lack a gall bladder. Their large intestines and ceca are moderately complex. Hamsters have a diploid chromosome number between 20 and 44. (Carleton and Musser, 1984; Nowak, 1999)

The record longevity for a wild hamster is ten years. This is an unusual case, however, and most wild and captive hamsters live two to four years. Common causes of mortality in the wild are predation, harsh winters, disease, and, in agricultural areas, crushing by heavy machinery. (Carey and Judge, 2002; Kayser, Weinhold, and Stubbe, 2003; Nowak, 1999)

Hamsters are terrestrial animals and their feet are modified for cursorial locomotion. Some hamsters can swim quite well by filling their cheek pouches with air, giving themselves buoyancy. They dig burrows with multiple entrances and many connected tunnels, with nest, latrine, and food storage chambers. Tunnels may be 50 cm deep, and even deeper during the winter--up to two meters below the soil surface. The size of a hamster's burrow often depends on the age of the animal. Hamsters are usually nocturnal or crepuscular, though some species are active both night and day, and they are solitary. Some species are highly aggressive toward conspecifics and strict dominance hierarchies help to assuage fighting. Often, females are the dominant animals. Hamsters are not true hibernators, but they do experience long bouts of torpor, lasting several weeks at a time, during the winter. (Carleton and Musser, 1984; Nowak, 1999)

Hamsters perceive visual, tactile, auditory, and chemical stimuli. They seem to rely most on vision when searching for live prey, but hearing and olfaction are also important (Langley 1985).

Hamsters use chemical cues to communicate. Males scent-mark their territories with their large sebaceous flank glands. In fact, the size of these glands is correlated with an individual's status in the dominance hierarchy: the larger the glands, the more dominant the animal. (Langley, 1985; Nowak, 1999)

Cricetines are primarily granivorous, but they also consume leaves, shoots, roots, and fruit. In addition, some species are omnivorous and eat insects and even vertebrates such as frogs. They cram food into their large cheek pouches and take it back to store in their burrows. Hamster burrows have been found with as much as 90 kg of stored food. (Carleton and Musser, 1984; Nowak, 1999)

Animals that prey on hamsters include diurnal raptors, snakes, and mammalian carnivores. Species that are known to eat hamsters are red kites, black kites, common buzzards, lesser spotted eagles, red foxes, domestic dogs, ermine, and Eurasian badgers. Predators such as common kestrels, grey herons, carrion crows, and rooks prey on juvenile hamsters.

Hamsters can be aggressive and do not hesitate to defend themselves from predators with their large incisors. Females sometimes protect their young from predators by carrying them in their cheek pouches. Finally, like the fur of most rodents, hamster fur comes in neutral colors, affording these animals some degree of camouflage. (Kayser, Weinhold, and Stubbe, 2003; Nowak, 1999)

As herbivores and carnivores, cricetines are primary, secondary, and in some cases, tertiary consumers. They are, in turn, food for various higher-level consumers. Their habit of storing seeds may mean that they play a role in seed dispersal. (Nowak, 1999)

Some hamster species feed on beans, corn, and lentils, and are thus considered crop pests. (Nowak, 1999)

Some hamster species thrive in captivity and make good pets, and they are also used in laboratories for behavioral and physiological research. Others are trapped for their skins. (Nowak, 1999)

The IUCN currently lists one species in this subfamily as endangered (the popular pet, golden or Syrian hamsters, Mesocricetus auratus), one as vulnerable (Romanian hamsters, Mesocricetus newtoni), and one as lower risk (gray dwarf hamsters, Cricetulus migratorius). Although hamsters breed readily and are abundant in captivity, wild populations of some species have restricted ranges and are vulnerable to habitat destruction. (IUCN, 2004; Nowak, 1999)