Cricetidae is an extremely diverse family of muroid rodents. This is one of the largest families of mammals, with 681 species in 130 genera and 6 subfamilies. The subfamilies of Cricetidae are: Arvicolinae (lemmings, voles, and muskrat), Cricetinae (hamsters), Lophiomyinae (crested rat), Neotominae (North American rats and mice), Sigmodontinae (New World rats and mice), and Tylomyinae (vesper rats and climbing rats). (Musser and Carleton, 2005)
Cricetids range throughout North America, South America, Europe, and most of Asia from southern China northwards. (Nowak, 1999)
Cricetids occupy a broad spectrum of habitats. Their range encompasses dry, wet, warm and cold climates. Habitats utilized by cricetids include grasslands, meadows, agricultural fields, forests, rocky mountain landscapes, deserts, suburban yards, human habitations, beaches, lakes, ponds, streams, marshes, swamps, and bogs. They also span a range of elevations from sea level to over 5000 meters above sea level. (Nowak, 1999)
Many cricetids are mouse-like or rat-like in appearance: they have small, somewhat elongated bodies, and are gray or brown with long tails, large eyes, and prominent ears and whiskers. However, body forms in this diverse group vary. Arvicolines, cricetines, and some sigmodontines have rounded bodies, with short tails, small eyes, and ears that are almost completely hidden in the fur. Pelage colors in this family include nearly every shade of brown and gray, including light golden brown, dark russet, and black. There is a tendency for the undersides to be paler, and many species have white bellies and chins. Pelage color may vary within cricetid species, as well, with two or more color morphs found in some populations. The texture of the fur ranges from silky and soft to coarse and spiny. Tails may be tufted, well-furred, or nearly naked. Cricetids are small (pygmy mice of the genus Baiomys weigh up to 8 grams) to large (muskrats, Ondatra zibethicus, weigh almost 2 kg) relative to other rodents. Sexual dimorphism varies across species: in some cases, males are larger than females, and in other cases, females are larger than males. Some species do not exhibit sexual dimorphism at all. There are various specializations for different lifestyles found in this group; for example, the long, powerful claws of long-clawed mole mice (Geoxus) are adapted for digging, whereas the partially webbed hind feet and rudder-like tails of muskrats are adapted for swimming.
Some cricetid species are monogamous, living in small family groups consisting of a mated pair and their offspring. Juveniles of some arvicoline species help in raising their younger siblings. Many, perhaps the majority, are polygynous or promiscuous, having many different mates throughout the year with whom they associate for only brief periods of time. (Gubernick and Teferi, 2000; Nowak, 1999)
Cricetid reproduction is characterized by large litters and short interbirth intervals. Most cricetids are able to breed when they are just a few months old. Female cricetids often have a postpartum estrus and mate shortly after giving birth (although sometimes implantation is delayed until the female stops lactating). In some species, ovulation is induced by the act of mating. Seasonality of reproduction varies with climate; cricetids in warm, constant climates are likely to breed year round, whereas those in variable climates are more likely to only breed at favorable times of the year (although even those that live in unfavorable climates have been known to breed year round, even bearing litters beneath the snow). Under ideal conditions (such as those in the laboratory), cricetids have been known to produce more than 12 litters per year. (Carleton and Musser, 1984; Nowak, 1999)
Female cricetids often build nests in which they raise their offspring, which range from altricial to precocial. Like all mammals, they provide their young with milk until the young are able to eat solid food. Male parental care, including grooming, carrying, and huddling, exists in some species and has been shown to enhance survival of the young (Gubernick and Teferi 2000). Time to independence is usually short, and juveniles of many species disperse and breed on their own the same year they are born. (Gubernick and Teferi, 2000; Nowak, 1999)
As is the case with most small muroid rodents, cricetids face vast array of predators and usually live less than a year in the wild. Lifespan in captivity is often much longer, up to a decade in some species. (Nowak, 1999)
Cricetids are diverse in their behavior, as they are in all of their other characteristics. Some species are exclusively arboreal, while others rarely leave the ground, and some spend most of their time burrowing beneath it. Some are adapted for an aquatic lifestyle and are excellent swimmers. Most, but not all, cricetids are nocturnal. Cricetids often use torpor during cold periods to lower their energy requirements or aestivate when it is hot. Many build nests or burrows in which they seek refuge during periods of inactivity. Some species are known to be solitary and highly territorial, while others live in small social groups or in large colonies. Most are fairly sedentary, but some undergo huge population cycles and may disperse over large distances during periods of overabundance. (Nowak, 1999)
Cricetids use vision, hearing, touch, smell, and taste to perceive the world. The relative importance of these senses varies among species and relates to each species' lifestyle. For example, fossorial species tend to have a reduced need for vision, and often have reduced eyes, but may have a keen tactile sense. Some cricetids produce (and therefore are likely to hear) sounds that surpass the range of human hearing (Smith 1972). Chemical signaling with pheromones and scent marks is an extremely important aspect of communication in this group, as these odors can quickly send a signal about the identity and status of an individual (Johnston 2003). In general, cricetids communicate using a combination of chemical, tactile, visual, and auditory cues--the relative importance of which varies among species. (Johnston, 2003; Smith, 1972; Johnston, 2003; Nowak, 1999; Smith, 1972)
Cricetids may be carnivores, omnivores, or herbivores. Food eaten by the group as a whole include leaves, pine needles, seeds, berries, fruits, roots, tubers, stems, twigs, nuts, fungi, insects, slugs, earthworms, aquatic crustaceans, spiders, small terrestrial vertebrates, and fish. Many cricetids are generalists that dine on many of these food items, while some are specialists that eat just one or two. Some cricetid species cache food for later use. (Nowak, 1999)
In order to avoid easy detection by predators, many cricetids are nocturnal. Their neutral-colored coats tend to blend in with the surroundings and afford some degree of camouflage. When alarmed, they seek refuge in trees, burrows, or other places where the predator cannot follow. As a last resort, cricetids often bite their attacker with their sharp incisors and utter high-pitched chirps. One unique cricetid species, Lophiomys imhausi, bears aposematic white and black patches, exudes a musky odor, and has erectile, stiff hairs that may mimic porcupines. (Carleton and Musser, 1984; Nowak, 1999)
Cricetids are valuable members of many ecosystems, in which they fulfill roles as predators, prey, and dispersers of seeds and mycorrhizal fungi. Fossorial species turn over earth as they dig and therefore aerate the soil. Cricetids have a large impact on forest succession by preying on tree seedlings, and are sometimes considered keystone species when they play such roles (Manson et al. 2001). Their high reproductive output and regular boom and bust cycles in population numbers result in dramatic impacts on their plant prey species and predators that rely mainly on cricetid prey. Many types of parasites use cricetids as hosts, including species of ticks and mites, fleas, lice, bot flies, nematodes, and flukes (Kinsella 1991). (Kinsella, 1991; Manson, et al., 2001; Nowak, 1999)
Some cricetid species, especially the hamsters, thrive in captivity and are popular pets. As research animals, cricetids have contributed greatly to the fields of ecology, physiology, and genetics. Some species are harvested for food or for their valuable fur. Also, cricetids play an important role in controlling populations of insect pests. (Nowak, 1999)
Some cricetids are vectors of human diseases, including hantavirus and lyme disease. Those that dwell in agricultural areas sometimes damage crops. Also, some species are considered nuisance animals when they enter homes, raid food stores, gnaw on household goods, and build nests in unwelcome places. (Nowak, 1999)
About 21% of the species in this family are included on the IUCN's Red List of Threatened Species. Of these, 58 are lower risk, 2 are near threatened, 27 are vulnerable, 27 are endangered, 11 are critically endangered, and 10 are lacking sufficient data. Another 6 (Pemberton's deer mice, Peromyscus pembertoni, Antillean giant rice rats, Megalomys desmarestii, Santa Lucia giant rice rats, Megalomys luciae, Darwin's Galapagos mice, Nesoryzomys darwini, indefatigable Galapagos mice, Nesoryzomys indefessus, and Nelson's rice rats, Oryzomys nelsoni) have gone extinct in recent years. Human-induced habitat loss and degradation threaten most of these species. Also, many cricetids have restricted geographic ranges, making them even more vulnerable to extinction. Few actions, other than basic research, are underway to conserve these and other rodent species, as most attention is directed toward saving larger, more charismatic fauna. (IUCN, 2004)
Allison Poor (author), University of Michigan-Ann Arbor, Tanya Dewey (editor), Animal Diversity Web.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
uses sound to communicate
living in landscapes dominated by human agriculture.
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
having coloration that serves a protective function for the animal, usually used to refer to animals with colors that warn predators of their toxicity. For example: animals with bright red or yellow coloration are often toxic or distasteful.
Referring to an animal that lives in trees; tree-climbing.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.
an animal that mainly eats meat
Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.
uses smells or other chemicals to communicate
used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.
helpers provide assistance in raising young that are not their own
active at dawn and dusk
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
in mammals, a condition in which a fertilized egg reaches the uterus but delays its implantation in the uterine lining, sometimes for several months.
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
union of egg and spermatozoan
an animal that mainly eats leaves.
A substance that provides both nutrients and energy to a living thing.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
Referring to a burrowing life-style or behavior, specialized for digging or burrowing.
an animal that mainly eats fruit
an animal that mainly eats seeds
An animal that eats mainly plants or parts of plants.
a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.
Found in northern North America and northern Europe or Asia.
ovulation is stimulated by the act of copulation (does not occur spontaneously)
An animal that eats mainly insects or spiders.
fertilization takes place within the female's body
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter).
marshes are wetland areas often dominated by grasses and reeds.
makes seasonal movements between breeding and wintering grounds
eats mollusks, members of Phylum Mollusca
Having one mate at a time.
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
an animal that mainly eats fungus
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
an animal that mainly eats all kinds of things, including plants and animals
found in the oriental region of the world. In other words, India and southeast Asia.
the business of buying and selling animals for people to keep in their homes as pets.
chemicals released into air or water that are detected by and responded to by other animals of the same species
an animal that mainly eats fish
the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
having more than one female as a mate at one time
"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
an animal that mainly eats dead animals
communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them
scrub forests develop in areas that experience dry seasons.
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
digs and breaks up soil so air and water can get in
places a food item in a special place to be eaten later. Also called "hoarding"
living in residential areas on the outskirts of large cities or towns.
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5? N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.
uses sound above the range of human hearing for either navigation or communication or both
living in cities and large towns, landscapes dominated by human structures and activity.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
breeding takes place throughout the year
young are relatively well-developed when born
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