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Species comparisons

From WhiskerWiki

This page attempts to provide a standardized side-by-side comparison of interspecific variation (variation that occurs when comparing individuals of differing species), 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 (within species) color variation.

Soricidae (shrews)

Over thirty species in the family Soricidae are present in the United States, representing four genera: Blarina, Cryptotis, Notiosorex, and Sorex.

Blarina (short-tailed shrews)

Blarina are relatively large shrews with short tails. Where their ranges overlap, they can be difficult to differentiate without careful measurement of size. In some areas, they may only be able to be differentiated using molecular methods. Species not pictured: Everglades Short-tailed Shrew (Blarina peninsulae) and Sherman's Short-tailed Shrew (Blarina shermani). Both Blarina peninsulae and Blarina shermani are similar in appearance to Blarina carolinensis and were once considered subspecies of Blarina carolinensis.

Cryptotis

Cryptotis are small shrews with very short tails and small ears that are often not clearly visible. Species not pictured: Berlandier's Least Shrew (Cryptotis berlandieri). Cryptotis berlandieri was previously considered a subspecies of Cryptotis parvus. It is similar in appearance, but averages slightly larger than Cryptotis parvus.

Notiosorex

Notiosorex are small, generally gray shrews with short tails and relatively large ears that are clearly visible. Species not pictured: Cockrum's Gray Shrew (Notiosorex cockrumi) and Ticul's Gray Shrew (Notiosorex tataticuli). Notiosorex cockrumi and Notiosorex tataticuli are similar in appearance to Notiosorex crawfordii. Notiosorex cockrumi was recognized by Baker et al. (2003) as species separate from Notiosorex crawfordi. Notiosorex tataticuli was recognized as a separate species by Camargo & Álvarez-Castañeda (2020), based on populations previously attributed to Notiosorex crawfordi.

Sorex (long-tailed shrews)

Members of Sorex have long tails, as the common name implies. For identification, note the difference in overall size, tail length, and coloration (dorsal, ventral, tail). However, use caution as color is not always a reliable character for differentiating between some Sorex species, particularly S. monticolus, S. obscurus, S. ornatus, and S. vagrans. Some species of Sorex may only be differentiated through careful examination of the teeth, comparison of skull measurements, or with the use of molecular methods. Confidently differentiating between S. cinereus and S. haydeni is accomplished only through genetic testing or karyotype analysis. Notice that S. tundrensis, S. ugyunak, and S. minutissimus have a bicolored or tricolored appearance. S. arcticus is also tricolored throughout much (but not all) of its range. S. trowbridgii is typically more dark gray in appearance but can lean toward brownish in parts of its range, such as California. Sorex longirostris and S. sonomae have a reddish dorsal coloration. Species not pictured: Eastern Water Shrew (Sorex albibarbis), Arizona Shrew (Sorex arizonae), Marsh Shrew (Sorex bendirii), Rock Shrew (Sorex dispar), Maryland Shrew (Sorex fontinalis), Saint Lawrence Island Shrew (Sorex jacksoni), Mount Lyell Shrew (Sorex lyelli), Pacific Shrew (Sorex pacificus), American Water Shrew (Sorex palustris), Pribilof Island Shrew (Sorex pribilofensis), Fog Shrew (Sorex sonomae).

Talpidae (moles)

Eight species in the family Talpidae are present in the United States: Star-nosed Mole (Condylura cristata), American Shrew Mole (Neurotrichus gibbsii), Hairy-tailed Mole (Parascalops breweri), Eastern Mole (Scalopus aquaticus), Northern Broad-footed Mole (Scapanus latimanus), Southern Broad-footed Mole (Scapanus occultus), Coast Mole (Scapanus orarius), Townsend's Mole (Scapanus townsendii). Note the scale for Scapanus townsendii; this is the largest mole in North America. Neurotrichus gibbsii is the smallest mole in North America.

Condylura cristata (Star-nosed Mole)

Condylura is a genus of moles that contains a single extant species, the Star-nosed Mole (Condylura cristata).

Neurotrichus gibbsii (American Shrew Mole)

Neurotrichus is a genus of moles that contains a single extant species, the American Shrew Mole (Neurotrichus gibbsii). It is the smallest species of mole in the Americas.

Parascalops breweri (Hairy-tailed Mole)

Parascalops is a genus of moles that contains a single extant species, the Hairy-tailed Mole (Parascalops breweri).

Scalopus aquaticus (Eastern Mole)

Scalopus is a genus of moles that contains a single extant species, the Eastern Mole (Scalopus aquaticus).

Scapanus

Species not pictured: Northern Broad-footed Mole (Scapanus latimanus), Southern Broad-footed Mole (Scapanus occultus). Note the scale for Scapanus townsendii; this is the largest mole in North America.

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)

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), Desert Woodrat (Neotoma lepida), 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), Common Marsh Rice Rat (Oryzomys palustris), Texas 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 and also quite similar across species. Differentiating between P. maniculatus 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. boylii and P. keeni have very long tails. Peromyscus polionotus is a relatively small member of this genus. Species not pictured: California Deermouse (Peromyscus californicus), Northern Baja Deermouse (Peromyscus fraterculus), Saxicoline Deermouse (Peromyscus gratus), Southern Deermouse (Peromyscus labecula), Northern White-ankled Deermouse (Peromyscus laceianus), Black-eared Deermouse (Peromyscus melanotis), 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)

Reithrodontomys are sometimes mistaken for Peromyscus or Mus musculus because its coloration (brownish above and light colored below) can appear (at first glance) similar. However, Reithrodontomys is a smaller cricetid (members of the family Cricetidae) than Peromyscus, and typically the ventral coloration is closer to gray or buff rather than white. Mus musculus typically has a yellowish flank line and the tail is brownish with a blackish tip. Unlike Peromyscus and Mus musculus, Reithrodontomys have incisors that are grooved—so look closely! Within Reithrodontomys note that R. fulvescens has a long tail (much longer than head and body length) and is large compared to other Reithrodontomys. 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

Species not pictured: Rattus norvegicus.

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), White-eared Pocket Mouse (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: Dark Kangaroo Mouse (Microdipodops megacephalus), Pallid Kangaroo Mouse (Microdipodops pallidus).

Zapodidae

Eight species in the family Zapodidae (jumping mice) are present in the United States. Jumping mice 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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