Chaetodipus fallax
San Diego Pocket Mouse
(Chaetodipus fallax) | |
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Range | |
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Taxonomic classification | |
Order: | Rodentia |
Suborder: | Supramyomorpha |
Infraorder: | Castorimorphi |
Family: | Heteromyidae |
Subfamily: | Perognathinae |
Genus: | Chaetodipus |
Binomial details | |
Chaetodipus fallax (Merriam, 1889) |
Description
From Lackey (1996): "Chaetodipus fallax is medium in size compared with other species of the genus. The upper parts of the pelage are rich brown, darker over the rump, and under parts are white or creamy white. Bristles on the rump are black, whereas those on the flank are white. The lateral line and subterminal portions of hairs of the upper parts are pinkish buff. The tail is long and crested, dark above and white below. The ears are dusky on the inflexed portion, and whitish on the inner surface."
From Patton and Alvarez-Castañeda (1999) for California subspecies C. fallax fallax, approximately western half of range in California: "This is a medium-sized pocket mouse with relatively short and rounded ears (less than 9 mm), distinct spines are present on the rump and flanks, the tail is long and both crested and pencillate, and the dorsal coloration ranges from a rich brown in specimens from along the coast to light grayish-brown at inland localities on the margins of the desert. A buff-colored lateral line is present, and the underparts are self-colored white or creamy-white.... The total length averages about 190 mm, tail about 105 mm, greatest length of skull about 26.6 mm, and maxillary tooth row length about 4 mm."
From Jameson & Peeters (2004): A medium-sized, brownish pocket mouse. There are conspicuous white, spiny hairs on the dorsum and sides and black spines on the rump. A buff stripe, or lateral line, separates the venter and dorsum. The tail is bicolored and crested. The heel of the hind foot is naked.

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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California | Jameson & Peeters (2004) | 176–200 | 88–118 | 21–26 | 15–18 | |
rangewide | Lackey (1996) | males: 191 (n=20); females: 187 (n=20) | males: 106 (n=10); females: 105 (n=10) | males: 24 (n=20); females: 23 (n=20) | males: 10 (n=20); females: 10 (n=20) |
Skull
Similar species
From Patton and Alvarez-Castañeda (1999): (for California subspecies C. fallax fallax): "This species really only needs comparison with C. californicus, with which it might be locally sympatric.... californicus is distinctly larger in size, with longer and obviously more square-topped as opposed to rounded ears.... Compared to other pocket mice which may be sympatric or nearly so, the rump spines of fallax will differentiate it from arenarius, baileyi and formosus, as will its buff lateral line. The rump spines of fallax are not nearly as well developed as in spinatus, where they extend onto the shoulders."
Species | Size | Pelage appearance | Postauricular patch | Subaruicular spot | Antitragus | Tail bicolored | Tail crest | Tail tuft | Rump spines | Lateral lines | Lateral line color |
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Chaetodipus californicus | medium to large | coarse | absent | absent | lobed | distinctly | present | present | present (and on flanks) | present | orangish-yellow |
Chaetodipus fallax | medium | coarse | absent | absent | lobed | distinctly | present | present | present | present | buff-colored |
Chaetodipus formosus | medium | smooth | absent | present | lobed | distinctly or indistinctly | present | present | absent | absent | - |
Chaetodipus penicillatus | medium | smooth to coarse | present; faint | absent | lobed | distinctly | present | present | absent | faint or absent | buff |
Chaetodipus rudinoris | large | smooth | absent | when present, it is small | lobed | indistinctly | present | present | absent | present | ochraceous |
Chaetodipus spinatus | medium to medium-large | coarse | absent | preset | lobed | distinctly | present | present | present | faint or absent | buff |
Perognathus longimembris | small | smooth | present; faint | when present, it is faint | absent | distinctly or indistinctly | absent | present | absent | absent or faint |
References
Jameson EW, Peeters HJ. 2004. Mammals of California (No. 66). Berkeley (CA, USA): University of California Press.
Lackey JA. 1996. Chaetodipus fallax. Mammalian Species (517):pp.1-6.
Patton JL, Alvarez-Castañeda ST, editors. 1999. Family Heteromyidae. Mamiferos del noroeste de México. La Paz (Baja California Sur, MX): Centro de Investigaciones Biológicas del Noroeste.
Merriam CH. 1889. Revision of the North American pocket mice. North American Fauna 1:1-29.