Perognathus flavus
Silky Pocket Mouse
(Perognathus flavus) | |
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Range | |
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Taxonomic classification | |
Order: | Rodentia |
Suborder: | Supramyomorpha |
Infraorder: | Castorimorphi |
Family: | Heteromyidae |
Subfamily: | Perognathinae |
Genus: | Perognathus |
Binomial details | |
Perognathus flavus (S. F. Baird, 1855) |
Description
The Silky Pocket Mouse has a compact and slender body. Its fur color varies depending on the subspecies and geographic location but typically ranges from yellowish-brown to grayish-brown, helping it blend in with its surroundings. It has short, rounded ears without a lobed antitragus, and tail is without crest or tuft.
From Best & Skupski (1994): "Upperparts are finely lined with black on ochraceous buff and in some subspecies yellowish-buff and pinkish-buff. The lateral line is faintly expressed in buff. Ventrally, P. flavus is white including the forelegs, but there may be a faint tawny suffusion. The tail is whitish ventrally, and dusky or buffy on the dorsum (Hall, 1981). The dorsal color is heavily overlain with blackish-tipped hairs in most subspecies, contrasting with the clear buffy postauricular patches and a narrow line without black tinge on the side adjacent to the white underparts (Williams et al., 1993). The silky pocket mouse is the smallest heteromyid (Best, 1993). Length of head and body averages ca. 60 mm or less, and length of tail aver ages < 57 mm and rarely is > 60 mm (Williams et al., 1993). The tail is shorter than length of head and body (usually ca. 85 %, range is 76-93% Hoffmeister, 1986). P. flavus has the shortest tail and smallest ratio of length of tail to head and body of any Perognathus (ratio averaging < 0.9, Williams et al., 1993)."
From Armstrong et al. (2010): "The hair is fine and silky, the pale buff to pinkish brown of the dorsum interspersed with black hairs. The overall darkness of the back varies geographically. The conspicuous buffy postauricular patch is generally almost twice as large as the ear."
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arrow points to the location of the postauricular patch of Perognathus flavus
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arrow points to the location of the subauricular patch of Perognathus flavus
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 |
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Colorado | Armstrong et al. (2010) | 95–118 | 41–58 | 12–18 | 4–7 | 6–9 |
not reported | Ceballos (editor, 2014) | 100–122 | 44–60 | 15–18 | 5–6 | 6–9 |
Texas | Schmidly & Bradley (2016) | 113 | 50 | 16 | 6–8 |
Color variation
This section shows some of the color variation present in Perognathus flavus. 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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Colorado, Weld County
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Oklahoma, Washita County
Similar species
From Best & Skupski (1994): "Perognathus flavus is smaller and has a relatively shorter, non-penciled tail than allopatric P. alticolus, P. inornatus and P. parvus. Compared with P. amplus, P. flavus has a non-penciled tail (Williams et al., 1993) that is shorter, and the tail always is shorter than length of head and body (Hoffmeister, 1986). Hind feet of P. flavus are shorter (length of hind foot rarely >18 mm in P. flavus and rarely <19 mm in P. amplus - Williams et al., 1993), it has a more conspicuous, pale-colored, postauricular patch, and the skull is smaller (Hoffmeister, 1986). Compared with P. fasciatus, P. flavus in the Great Plains is smaller with more inflated auditory bullae and narrower interbullar region (Williams et al., 1993). In addition, P. flavus has a shorter tail, conspicuous postauricular patches, and a shorter, broader skull (Osgood, 1900). Compared with P. flavescens, P. flavus has narrower interparietals (width averages >4.0 mm in Great Plains populations of P. flavescens and <3.6 mm in P. flavus, it generally has a darker color dorsally due to numerous black-tipped guard hairs, and its postauricular patch appears larger and contrasts more with surrounding areas than in P. flavescens (Williams et al., 1993). Body size of P. flavescens is ca. 18% larger than sympatric P. flavus, with a relatively longer tail (length of tail averages 86 % of length of head and body in P. flavus). The skull of P. flavescens is ca. 11% longer than that of P. flavus, with relatively smaller bullae (length of bullae averages 40 % of occipitonasal length in P. flavus, and 37 % in P. flavescens), and wider interorbital region (interorbital breadth averages > 5.1 mm in P. flavescens and <4.5 mm in P. flavus - Williams, 1978). Compared with P. flavescens in Arizona, the tail of P. flavus averages ca. 80 -90% of length of head and body rather than ca. 92 %, the hind foot is smaller (averaging 16.8 rather than 19.4 mm), the skull is smaller, the width of interparietal is less than length of maxillary toothrow, the interorbital region is narrower , and the skull is narrower across the mastoids (Hoffmeister, 1986). Compared with P. flavescens in New Mexico, which usually has a length of tail 60 mm, total length 120 mm, and length of cranium >21 mm, P. flavus usually has a tail <60 mm, total length < 120 mm, and length of cranium <21 mm (Findley et al., 1975). Perognathus flavus differs from P. longimembris in having an absolutely and relatively shorter, non-penciled tail, smaller average size, smaller hind feet, narrower interorbital width, and wider upper molars (Williams et al., 1993). In addition, the nasals of P. flavus are shorter (Hoffmeister, 1986). The ranges of P. flavus and P. merriami overlap in southeastern New Mexico and western Texas (Bailey, 1905; Osgood, 1900). P. flavus is more similar to P. merriami than to any other species of Perognathus; these taxa may hybridize at a few localities. Compared with P. merriami, P. flavus has: a shorter tail; longer, softer and laxer pelage; darker, more-contrasting mid-dorsal color with a pinkish rather than yellowish or yellowish-orange hue; larger postauricular spots; larger, more-inflated auditory bullae; narrower interorbital and interparietal widths; wider P4 (Williams et al., 1993); smaller translacrimal width; longer ears; smaller length of head and body, length of tail, and length of hind foot. Relative to greatest length of skull, P. flavus has longer maxillary toothrows and bullae, shorter and less projecting nasals, greater transdental width, and smaller interorbital breadth (Anderson, 1972). No single set of characters will distinguish all P. flavus from all P. merriami."
Skull characters
From Armstrong et al. (2010): "The interparietal bone is narrower than the interorbital breadth of the skull."
References
Anderson S. 1972. Mammals of Chihuahua: taxonomy and distribution. Bulletin of the American Museum of Natural History 148:149-410.
Armstrong DM, Fitzgerald JP, Meaney CA. 2010. Mammals of Colorado, Second Edition. Denver (CO, USA): University Press of Colorado.
Bailey V. 1905. Biological survey of Texas. North American Fauna 25:1-222.
Baird SF. 1855. Characteristics of some new species of Mammalia, collected by the U.S. and Mexican Boundary Survey, Major W. H. Emory, U.S.A. Commissioner. Proceedings of the Academy of Natural Sciences of Philadelphia 7:331-333.
Best TL. 1993. Patterns of morphologic and morphometric variation in heteromyid rodents. Pp. 197-235, in Biology of the Heteromyidae (H. H. Genoways and 1. H. Brown, eds.). Special Publication, The American Society of Mammalogists 10:1-719.
Best TL, Skupski MP. 1994. Perognathus flavus. Mammalian Species (471):pp.1-10.
Ceballos G, editor. 2014. Mammals of Mexico. Baltimore (MD, USA): Johns Hopkins University Press.
Findley J, Harris SAH, Wilson DE, Jones C. 1975. Mammals of New Mexico. Albuquerque (NM, USA): University of New Mexico Press.
Hall ER. 1981. The mammals of North America. Second edition. New York (NY, USA): John Wiley & Sons 1:1-600 + 90.
Hoffmeister DF. 1986. Mammals of Arizona. Tucson (AZ, USA): University of Arizona Press.
Osgood WH. 1900. Revision of the pocket mice of the genus Perognathus. North American Fauna 18:1-73.
Schmidly DJ, Bradley RD. 2016. The mammals of Texas. Austin (TX, USA): University of Texas Press.
Williams DF. 1978. Systematics and ecogeographic variation of the Apache pocket mouse (Rodentia: Heteromyidae). Bulletin of Carnegie Museum of Natural History 10:1-57.
Williams DF, Genoways HH, Braun JK. 1993. Taxonomy. Pp. 38-196, in Biology of the Heteromyidae (H.H. Genoways and J. H. Brown, eds.). Special Publication, The American Society of Mammalogists 10:1-719.