Calomyscus bailwardi is found in the Paleartic regions of Iran, Afghanistan, Pakistan, Caucasus, and southern Russia.

Biogeographic Regions: palearctic (Native )

Mouselike hamsters were once grouped with the New World Peromyscus, due to their appearance, though they are now grouped with the Old World hamsters. The single morphological feature that distinguishes Calomyscus from Peromyscus is that the genus Calomyscus has four-rooted molar teeth.

Mouselike hamsters have a jaw in which the angular process on the mandible is in line with the rest of the jaw. This sciurognathous jaw is characteristic of the family Muridae. The zygomatic plate is broad and tilted upward. The infraorbital foramen is relatively large and is in the shape of a V, wider dorsally than ventrally. The large size of the infraorbital foramen allows a slip of the masseter muscle to pass through it. The auditory bullae are large and the pterygoid extends to the bullae. The dental formula is 1/1 0/0 0/0 3/3 = 16. The upper incisors have a smooth anterior surface and are covered in yellowish-brown enamel. All of the cheek teeth lack closed ridges of dentine and show only traces of cusps.

Mouselike hamsters weigh only 15 to 30 grams, on average weighing 20.4 g. There is no sexual dimorphism. Females have six mammae. Their bodies measure 61 to 98 mm, while their tails add an additional 72 to 102 mm, making the tail longer than both the head and body. The vibrissae are up to 21 mm long. The ears are very round and 17 to 20 mm long. The ears are devoid of hair and are pinkish-grey to slate gray in color. Their fur is very soft, fine, plumbeous at the base, and long, and ranges from a light pink-brown to a gray-brown color on the upper part of the body, and their underside, hands, and feet are white. The dividing line between the back and the belly is very well defined. There is no white patch behind the ear or eye, as in some other members of the Muridae. The tail is covered with short brown hairs and ends with a small tassel of hair. Calomyscus bailwardi lacks cheek pouches. The muzzle is sharp and pointed. The hind leg is elongated in comparison to the forelimb. The hindfeet have five digits each, and the forefeet each have five digits with a vestigial clawless thumb. The claws are delicate and small.

Range mass: 15 to 30 g.

Average mass: 20.4 g.

Range length: 133 to 200 mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike

• Terrestrial

Calomyscus bailwardi favors mountain steppe regions between 400 and 3,500 meters, and is typically absent from low valleys. It is commonly found in forests at intermediate latitudes under evergreens as well as on barren hills. It favors crevices between stone walls and embankments in small fields and terraced cultivation. In these crevices nests made of woven grass, wool, and other various soft materials have been found.

Range elevation: 400 to 3500 m.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: forest ; mountains

Other Habitat Features: agricultural

Mouselike hamsters are partly granivorous as well as herbivorous, eating seeds, grasses, flowers, and leaves. Like many other members of Muridae, C. bailwardi brings back food to its home, though it cannot carry large quantities due to its lack of cheek pouches. It conceals the caches of food under stones in its burrow. These caches are most likely utilized during the winter months when the climate is harsh. Captive mouselike hamsters ate chopped vegetables and millet seeds, and they drank water, which is rarely available to them in the wild.

Plant Foods: leaves; seeds, grains, and nuts; flowers

Foraging Behavior: stores or caches food

Primary Diet: herbivore (Folivore , Granivore )

Mouselike hamsters are part of the food chain and are preyed on by local wildlife, depending on the region in which they are being observed.

Cases have been documented in which mouselike hamsters were found living in the burrows of Meriones persicus. Since C. bailwardi is not a good burrower, it is thought that they moved into burrows that were already vacated.

Mouselike hamsters are seed predators and dispersers. If they do not consume all of the seeds that they store for use during the winter, the seeds can sprout the following spring.

Ecosystem Impact: disperses seeds

The small size and lack of defenses allows mouselike hamsters to be very susceptible to predation. The most common predators of mouselike hamsters are owls, martens, polecats, and snakes.

Known Predators:

• pallid scops owls (Otus brucei)
• marbled polecats (Vormela peregusna)
• stone martens (Martes foina)
• levantine vipers (Macrovipera lebetina obtusa)
• rat snakes (Sphalerosophis atriceps)

No information is available on communication or perception channels of C. bailwardi.

Perception Channels: visual ; acoustic

Captive C. bailwardi typically live for around 4 years. The longest recorded life of C. bailwardi is 9 years, 3 months, and 18 days, which occurred in captivity. The only studies done on C. bailwardi have been in captivity, so the lifespan in the wild is not known.

Average lifespan

Status: captivity: 9.75 years.

Average lifespan

Status: captivity: 4 years.

Average lifespan

Status: captivity: 9.4 years.

Not much is known of the mating systems of mouselike hamsters. They are not thought to be highly social mammals, though they have occasionally been known to share shelter sites in the wild, and they huddle together in captivity.

The breeding season of C. bailwardi is long, with the peak breeding time ranging from late March to early June. However, the breeding period can vary regionally, depending on food availability. Females have been known to produce up to two litters during this time span. Each litter produces 1 to 5 young. The sex ratio in newborns is equal. Young are weaned no earlier than 4 weeks. Female C. bailwardi have 6 mammae to feed their young.

The highest recorded number of births to a single female was recorded in captivity as 15 litters in 2.25 years, with a total of 41 young produced. In the wild, the typical female is sexually and reproductively active until the 3rd year of life.

Breeding interval: Mouselike hamsters produce two litters per year, during 1 breeding period that takes place in late spring to mid-summer

Breeding season: The breeding season is from late spring to mid-summer, typically from late March to early June.

Range number of offspring: 1 to 5.

Average number of offspring: 2.8.

Range gestation period: 3 to 5 weeks.

Range weaning age: 4 (low) weeks.

Range time to independence: 4 to 8 months.

Average age at sexual or reproductive maturity (female): 4 months.

Average age at sexual or reproductive maturity (male): 5 months.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Average number of offspring: 3.3.

The young of C. bailwardi are hairless and are helpless for the first 13 days of their lives, until they can open their eyes for the first time. Around this same time, gray fur can be seen, though the young will not have the same coloring or size as adults until they are 4 to 8 months old. This is a relatively long period of growth and development for members of the family Muridae.

Young achieve a doubling in weight by the 8th day. Weaning occurs no earlier than the 4th week of life, and growth typically finishes around the 4th month of life when the mouselike hamster reaches an eight- to ninefold body weight in comparison to the birthweight, though growth can continue for up to 8 months.

In one instance, cannibalism was observed. A captive female C. bailwardi ate its young.

Parental Investment: altricial ; female parental care ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female); post-independence association with parents

There is very little information on the status of C. bailwardi.

IUCN Red List of Threatened Species: least concern

In areas where mouselike hamsters are abundant, they may behave as agricultural pests and harbor diseases to which humans are susceptible.

Negative Impacts: injures humans (carries human disease); crop pest

Mouselike hamsters have been used in Russia for various tests in labs and are sold as pets in many pet stores. They also have been imported by the United Kingdom for exhibits in zoos.

Positive Impacts: pet trade ; research and education