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Side-by-side comparison of mice, rats, lemmings, and voles

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This page attempts to provide a standardized side-by-side comparison of interspecific variation for species of Cricetidae, Heteromyidae, Muridae, and Zapodidae, which can be helpful for identification. Standardized images for some species are not available, yet. For species not represented with an image here, images from the field are typically available on the individual species pages. Adults in summer pelage are shown unless otherwise noted. This page does not show the full variation in color for each species so we have added a ☆ next to the names of species that have a high degree of intraspecific color variation.

Cricetidae

Alexandromys oeconomus (Root Vole)

Arborimus (tree voles)

Species not pictured: White-footed Vole (Arborimus albipes), Red Tree Vole (Arborimus longicaudus), Sonoma Tree Vole (Arborimus pomo).

Baiomys taylori (Northern Pygmy Mouse)

Species not pictured: Northern Pygmy Mouse (Baiomys taylori)

Clethrionomys (=Myodes) (red-backed voles)

Species not pictured: Western Red-backed Vole (Clethrionomys californicus).

Dicrostonyx (collared lemmings)

Species not pictured: Nelson's Collared Lemming (Dicrostonyx nelsoni), Unalaska Collared Lemming (Dicrostonyx unalascensis).

Lemmiscus curtatus (Sagebrush Vole)

Lemmus (true lemmings)

Species not pictured: Nearctic Brown Lemming (Lemmus trimucronatus).

Microtus (meadow voles)

Species not pictured: Gray-tailed Vole (Microtus canicaudus), Rock Vole (Microtus chrotorrhinus), Florida Salt Marsh Vole (Microtus dukecampbelli), Mogollon Vole (Microtus mogollonensis), Townsend's Vole (Microtus townsendii).

Mictomys borealis (Northern Bog Lemming)

Species not pictured: Northern Bog Lemming (Mictomys borealis). Until recently, Mictomys borealis was considered a species in the genus Synaptomys. Hope et al. (2023) provides multiple lines of evidence that supports the recognition of northern bog lemmings as Mictomys borealis, distinct at the generic level from Synaptomys.

Neotoma (woodrats, pack rats)

Woodrats, also called pack rats for their collecting behavior, are fairly big rodents. They look like very large deer mice. They have stout bodies and long tails. The pelage of Neotoma has a smooth appearance, unlike the grizzled appearance of cotton rats. Species not pictured: Bryant's Woodrat (Neotoma bryanti), Arizona Woodrat (Neotoma devia), Dusky-footed Woodrat (Neotoma fuscipes), White-toothed Woodrat (Neotoma leucodon), Big-eared Woodrat (Neotoma macrotis), Allegheny Woodrat (Neotoma magister), Southern Plains Woodrat (Neotoma micropus). Note the relatively large ears on Neotoma albigula. Neotoma cinerea have bushy tails.

Phenacomys (heather voles)

Species not pictured: Eastern Heather Vole (Phenacomys ungava). As a juvenile or subadult, Phenacomys intermedius may be mistaken for Lemmiscus curtatus. As an adult, Phenacomys intermedius species may be confused with Microtus montanus.

Ochrotomys nuttalli (Golden Mouse)

The Golden Mouse (Ochrotomys nuttalli) has a very distinctive coat coloration that is golden-yellowish-orange to yellowish-brown above and whitish-orange below.

Onychomys (grasshopper mice)

Onychomys are Peromyscus-looking mice with very short tails. Species not pictured: Chihuahuan Grasshopper Mouse (Onychomys arenicola).

Oryzomys (marsh rice rats)

Species not pictured: Coues's Marsh Rice Rat (Oryzomys couesi), Northeastern Marsh Rice Rat (Oryzomys palustris), Northwestern Marsh Rice Rat (Oryzomys texensis).

Peromyscus (deer mice)

Peromyscus contains species that are often extremely difficult to differentiate unless careful measurements are taken or genetic testing is conducted. Coloration is not always a reliable character as it can be quite variable, but also quite similar across species. Differentiating between P. maniculatus (sensu lato, which includes P. maniculatus, P. sonoriensis, P. gambelii, P. labecula, and P. melanotis) and P. leucopus using external characters is notoriously difficult in certain parts of the country and genetic testing may be required in order to be certain. While most of the Peromyscus look similar at first glance, P. truei has significantly larger ears (in most of its range) and P. keeni have very long tails. Peromyscus polionotus is a relatively small member of this genus. Species not pictured: California Deermouse (Peromyscus californicus), Saxicoline Deermouse (Peromyscus gratus), Southern Deermouse (Peromyscus labecula), Northern White-ankled Deermouse (Peromyscus laceianus), Merriam's Deermouse (Peromyscus merriami).

Podomys floridanus (Florida Mouse)

The Florida Deermouse (Podomys floridanus) is endemic to Florida. It is a large Peromyscus-looking mouse. It is the only species in the genus Podomys.

Reithrodontomys (harvest mice)

Five species of Reithrodontomys are present in the United States. Members of Reithrodontomys are small and sometimes mistaken for Mus musculus and Peromyscus (particularly R. megalotis and R. montanus). The presence of grooves on the upper incisors will separate Reithrodontomys from Peromyscus. Where R. megalotis and R. montanus are sympatric, careful measurements of the body and tail length can help to differentiate these two very similar-looking species. Species not pictured: Salt-marsh Harvest Mouse (Reithrodontomys raviventris), an endangered harvet mouse endemic to the San Francisco Bay Area salt marshes in California, which looks similar to Reithrodontomys megalotis.

Sigmodon (cotton rats)

Sigmodon are recognized by their stout body, coarse and grizzled pelage, and somewhat short ears. The name Sigmodon refers to the more or less "S" shape formed by the cusps on the molars, especially those of the third molar. Species not pictured: Arizona Cotton Rat (Sigmodon arizonae), Tawny-bellied Cotton Rat (Sigmodon fulviventer), Yellow-nosed Cotton Rat (Sigmodon ochrognathus). Sigmodon ochrognathus has a conspicuous "yellow" nose. Sigmodon fulviventer has underparts that are distinctly brownish, buffy, or fulvous, extending from throat to anus. Sigmodon hispidus and Sigmodon arizonae look superficially similar but are allopatric (ranges do not overlap).

Synaptomys cooperi (Southern Bog Lemming)

Muridae

Three species in the family Muridae are present in the United States: Mus musculus, Rattus norvegicus, Rattus rattus. Murids are not native to the Americas; however these three species have been introduced nearly worldwide.

Mus musculus (House Mouse)

Rattus

From Best & Hunt (2020): "Brown rats are similar in appearance to roof rats, but roof rats generally are smaller and have a tail greater than 50% of total length. The rostrum of brown rats is blunter than that of roof rats, and the overall shape of the body is broader in brown rats."

Heteromyidae

The family Heteromyidae contains members of the genera Chaetodipus, Perognathus, Dipodomys, Heteromys, and Microdipodops.

Chaetodipus, Perognathus (pocket mice)

Like all species in the family Heteromyidae, pocket mice have external fur-lined cheek pouches, which are visible when viewed from the underside. Perognathus generally have smoother pelage and softer appearance than Chaetodipus. The overall darkness of the back varies geographically in most species. All Perognathus species lack rump spines, while only some Chaetodipus lack rump spines. The presence of rump spines may be difficult to detect in some species, such as Chaetodipus intermedius. Species of Perognathus and Chaetodipus can often be separated by a combination of the following characters: overall body size, presence/absence of tufted tail, presence/absencce of a crested tail, presence/absence of an antitragus (look closely at the ear), presence/absence of a subauricular spot, presence/absence of a postauricular spot, size of the postauricular spot (if present), presence/absence of rump spines.

Species not pictured: Highland Coarse-haired Pocket Mouse (Chaetodipus collis), San Diego Pocket Mouse (Chaetodipus fallax), Peninsular Pocket Mouse (Chaetodipus rudinoris), Spiny Pocket Mouse (Chaetodipus spinatus), No common name found for Perognathus alticola, Arizona Pocket Mouse (Perognathus amplus) ☆, Olive-backed Pocket Mouse (Perognathus fasciatus), Merriam's Pocket Mouse (Perognathus merriami), Columbia Plateau Pocket Mouse (Perognathus parvus). Perognathus mollipilosus was split from Perognathus parvus by Riddle et al. (2014) based on analyses of both mitochondrial DNA (mtDNA) and nuclear DNA (nDNA).

Dipodomys (kangaroo rats)

Like all species in the family Heteromyidae, kangaroo rats have external fur-lined cheek pouches, which are visible when viewed from the underside. Successful field identification of Dipodomys can, for the most part, be accomplished using a one or more of the following: range, tail coloration (particularly the distal portion), length of ear, length of tail, and number of toes (4 or 5). Species not pictured: Agile Kangaroo Rat (Dipodomys agilis), California Kangaroo Rat (Dipodomys californicus), Gulf Coast Kangaroo Rat (Dipodomys compactus), Desert Kangaroo Rat (Dipodomys deserti), Texas Kangaroo Rat (Dipodomys elator), Heermann's Kangaroo Rat (Dipodomys heermanni), Giant Kangaroo Rat (Dipodomys ingens), San Joaquin Kangaroo Rat (Dipodomys nitratoides), Panamint Kangaroo Rat (Dipodomys panamintinus), Dulzura Kangaroo Rat (Dipodomys simulans), Banner-tailed Kangaroo Rat (Dipodomys spectabilis), Stephens's Kangaroo Rat (Dipodomys stephensi), Narrow-faced Kangaroo Rat (Dipodomys venustus).

Heteromys irroratus (Mexican Spiny Pocket Mouse)

Species not pictured: Mexican Spiny Pocket Mouse (Heteromys irroratus).

Microdipodops (kangaroo mice)

Species not pictured: Pallid Kangaroo Mouse (Microdipodops pallidus).

Zapodidae

Species in the family Zapodidae are referred to as jumping mice. They have elongated hind limbs and remarkably long tails that are not well-haired (lack crests and tufts).

Napaeozapus (Woodland Jumping Mice)

Genetic analyses by Malaney et al. (2017) recognized 2 species within the genus Napaeozapus, where previous morphology-based studies had recognized only one species (e.g. Krutzsch, 1954). The work of Malaney et al. (2017) has importantly exposed cryptic diversity and a putative new species within Napaeozapus, but further studies will be needed to fully understand new species boundaries and morphological variation. Both species look similar to Zapus, but can be distinguished externally by the white-tipped tail and overall brighter coloration.

Zapus (Jumping mice)

Malaney et al. (2017) recognized 9 species within the genus Zapus, elevating some of the subspecies in Krutzsch's (1954) revision of jumping mice to species status. The work of Malaney et al. (2017) has importantly exposed cryptic diversity and putative new species within Zapus, but further studies will be needed to fully understand new species boundaries and morphological variation. Species not pictured: Southern Meadow Jumping Mouse (Zapus luteus), Central Pacific Jumping Mouse (Zapus montanus), Oregon Jumping Mouse (Zapus oregonus), Southern Pacific Jumping Mouse (Zapus pacificus). Zapus luteus was previuosly considered a subspecies of Zapus princeps by Krutszsch (1954). Zapus oregonus and Zapus pacificus were previously considered subspecies of Zapus princeps by Krutszsch (1954). Zapus montanus was previously considered a subspecies of Zapus trinotatus by Krutszsch (1954).

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