Peromyscus keeni
| Northwestern Deermouse
(Peromyscus keeni) | |
|---|---|
| Range | |
 | |
| Taxonomic classification | |
| Order: | Rodentia |
| Suborder: | Supramyomorpha |
| Infraorder: | Myomorphi |
| Superfamily: | Muroidea |
| Family: | Cricetidae |
| Subfamily: | Neotominae |
| Tribe: | Peromyscini |
| Genus: | Peromyscus |
| Binomial details | |
| Peromyscus keeni (Rhoads, 1894) | |
| Other resources | |
| Full taxonomic details at MDD | |
The Northwestern Deermouse (Peromyscus keeni) is a large Peromyscus that occurs in Washington, British Columbia, and southern Yukon Territory.
Description
From Naughton (2012) for Canada: "Fur colour and body size vary considerably across the range, and this mouse is inclined toward gigantism in isolated island populations. Generally, the dorsal fur is brown, reddish-brown, or dark grey-brown with a darker brown band of colour running along the spine from the head to the rump, but some island populations are dark brown with a blackish dorsal dorsal band. Belly and chest hairs are mostly white or pale grey at their tips with dark grey roots, but some island populations have buffy to reddish-brown tips on their belly and chest fur. Some animals have a small patch of hairs under their chin that are white all the way to the root. Hairs on the upper surface of the front feet are white, but on the same part of the hind feet the fur may be white, pale silvery grey, or dark brown or even partially dark brown with white toes on a few animals. The large eyes are black, bulging, and luminous. Vibrissae are long and constantly in motion when the mouse is active. Ears are long and mostly covered with a thin layer of fine, very short, dark hairs. The long tail is sharply bicoloured, dark brown above and white below, with a tuft of stiff hairs at the tip that are 4–5 mm in length. Juveniles undergo two maturational moults before achieving their adult pelage, after which they moult once annually in late summer. Juveniles are usually dark grey above and grey to silver-grey below, while subadults are dark brown above and silver-grey to white below."
External measurements
Length measurements are in millimeters (mm) and weight measurements are in grams (g), unless stated otherwise. If available, the sample size (n=) is provided. If a range is not provided and n= is not given, then the listed measurement represents an average.
| Part of range | Reference | Total length | Tail length | Hindfoot length | Ear length | Mass |
|---|---|---|---|---|---|---|
| Canada | Naughton (2012) | 140–263 | 70–126 | 19–32 | 12–26 | 15.0–52.4 |
Color variation
This section shows some of the color variation present in Peromyscus keeni. The location is provided for reference only. The individual shown does not necessarily represent the only color variant within the local population.
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juvenile, Clark County, Washington -
Washington, Skamania County
Skull
The holotype for the species (ANSP 7768) is located in the Academy of Natural Sciences of Drexel University located in Philadelphia, Pennsylvania. Images are not currently available. Images of the skull of an individual from Washington are shown below.
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NEON05G15. Dorsal view of the skull of Peromyscus keeni. -
NEON05G15. Lateral view of the skull of Peromyscus keeni. Lower mandible not shown. -
NEON05G15. Ventral view of the skull of Peromyscus keeni. -
NEON05G15. Upper incisors of Peromyscus keeni. -
NEON05G15. Dorsal view of the lower mandible of Peromyscus keeni.
Similar species
Comparison with Peromyscus sonoriensis
From Naughton (2012): "While chromosomally distinct from Deer Mice [Peromyscus maniculatus (sensu lato)], there are, unfortunately, no completely reliable physical traits that will distinguish all Keen's Mice from Deer Mice in the field... The following formula using diastema length (the gap between the back of the incisors and front edge of the molars) and tail length separates the two species in the southern part of their range, including Washington State and Vancouver Island and the surrounding islands: 4.4 x length of tail (in mm) + length of mandibular diastema (in mm). Animals with a score of ≥ 436 are Keen's Mice, while those with scores of < 436 are Deer Mice. The efficacy of this formula, when applied to inland and more northerly populations has not yet been assessed, and the formula is ineffective in identifying living animals."
The following is from Zheng et al. 2003. Their analysis included northwestern populations of Peromyscus maniculatus sensu lato, which are now recognized as Peromyscus sonoriensis: "The only widely used criteria for distinguishing P. keeni and P. maniculatus in the field are tail length and the ratio of tail to head + body (Sheppe 1961; Allard et al. 1987). Allard et al. (1987) used the criterion of tail length > 96 mm to distinguish adult P. keeni (designated as P. oreas in their paper) from P. maniculatus. Our data confirmed the general validity of this criterion. In our samples, all the maniculatus individuals with tail length > 95 mm were found either in northwestern Oregon or on Vancouver Island, indicating an uneven distribution of long-tailed maniculatus individuals.... Individuals belonging to the P. keeni clade typically have longer tails and a higher tail to head + body ratio than those of the P. maniculatus clade. The absolute tail length distinguishes the keeni clade more strongly than the ratio of tail to head + body. Among individuals of the P. keeni clade, 94% had tail length ≥ 95 mm; among P. maniculatus 91% had tail length < 95 mm (Fig. 5a). Among individuals of the P. keeni clade, 88% had a tail to head + body ratio ≥ 1.10; among P. maniculatus, 81% had a tail to head + body ratio < 1.10." See the figure from Zheng et al. (2003).
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Western Deermouse (Peromyscus sonoriensis), long-tailed population in Washington -
Northwestern Deermouse (Peromyscus keeni)
References
Hogan KM, Hedin MC, Koh HS, Davis SK, Greenbaum IF. 1993. Systematic and taxonomic implications of karyotypic, electrophoretic, and mitochondrial-DNA variation in Peromyscus from the Pacific Northwest. Journal of Mammalogy 74(4): 819-831.
Naughton D. 2012. The natural history of Canadian mammals. Toronto (ON, CA): University of Toronto Press.
Rhoads SN. 1894. Descriptions of four new species and two subspecies of White-footed mice from the United States and British Columbia. Proceedings of the Academy of Natural Sciences of Philadelphia 46, 258.
Zheng X, Arbogast BS, Kenagy GJ. 2003. Historical demography and genetic structure of sister species: deermice (Peromyscus) in the North American temperate rain forest. Molecular Ecology 12(3):711-724.