Neotamias senex
| Shadow Chipmunk
(Neotamias senex) | |
|---|---|
| Range | |
 | |
| Taxonomic classification | |
| Order: | Rodentia |
| Suborder: | Sciuromorpha |
| Family: | Sciuridae |
| Subfamily: | Xerinae |
| Tribe: | Tamiini |
| Genus: | Neotamias |
| Binomial details | |
| Neotamias senex (J. A. Allen, 1890) | |
| Other resources | |
| Full taxonomic details at MDD | |
The Shadow Chipmunk (Neotamias senex) is a small chipmunk that occurs in forested areas in the Sierra Nevada Range of California, northwestern California to the coast, the eastern portion of the Cascade Range of Oregon, and extreme western Nevada (Verts and Carraway, 1998).
Description
From Gannon and Forbes (1995): "senex is a large chipmunk characterized by the grayish pelage, especially on the top of the head and on the rump and thighs, more noticeable in winter pelage (Merriam, 1897). Except for the dark median dorsal stripe, the markings on the body are relatively indistinct. The tail is comparatively short, narrow, pale fulvous underneath and at the base of hairs on the upper side, and has an indistinctly buffy edging. The fully furred ears have a conspicuous white third posteriorly in all pelages making postauricular spots sharply defined and obvious (Johnson, 1943). Pelage coloration varies from an overall dark pelage and obscure dorsal stripes along the coastal portion of the range of senex, to grayish-ochraceous general coloration with conspicuous dorsal stripes and white dorsum inland in the Sierra-Nevada Mountains of California (Johnson, 1943)."
Museum images
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Holotype: USNM 186461. Neotamias senex senex. Adult, sex undetermined. Summit of Donner Pass, Placer County, California. Collected 1 July 1885. -
Holotype: USNM 186461. Neotamias senex senex. Adult, sex undetermined. Summit of Donner Pass, Placer County, California. Collected 1 July 1885. -
Holotype: USNM 186461. Neotamias senex senex. Adult, sex undetermined. Summit of Donner Pass, Placer County, California. Collected 1 July 1885.
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 |
|---|---|---|---|---|---|---|
| California | Jameson & Peeters (2004) | 229–258 | 95–112 | 35–38 | 18–24 | 70–98 |
| Oregon | Verts & Carraway (1998) | females: 225–252 (n=30); males: 223–252 (n=30) | females: 87–115 (n=30); males: (78–112 (n=30) | females: 33–38 (n=30); males: 31–38 (n=30) | females: 73.8–100.0 (n=11); males: 72.4–103.1 (n=25) |
Skull
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Holotype: USNM 186461. Neotamias senex senex. Adult, sex undetermined. Summit of Donner Pass, Placer County, California. Collected 1 July 1885. Dorsal view of the skull. -
Holotype: USNM 186461. Neotamias senex senex. Adult, sex undetermined. Summit of Donner Pass, Placer County, California. Collected 1 July 1885. Ventral view of the skull. -
Holotype: USNM 186461. Neotamias senex senex. Adult, sex undetermined. Summit of Donner Pass, Placer County, California. Collected 1 July 1885. Lateral view of the skull. -
Holotype: USNM 186461. Neotamias senex senex. Adult, sex undetermined. Summit of Donner Pass, Placer County, California. Collected 1 July 1885. Dorsal view of the mandible. -
Holotype: USNM 186461. Neotamias senex senex. Adult, sex undetermined. Summit of Donner Pass, Placer County, California. Collected 1 July 1885. Lateral view of the left mandible.
Similar species
Comparison with Neotamias quadrimaculatus
From Kelt et al. (2023): "Tamias quadrimaculatus and T. senex are closely related and they share similar ecological requirements (Grinnell and Storer 1924; Johnson 1943; Sutton 1995). They may be very challenging to distinguishable in the field (Sutton 1995), and they are known to hybridize (Frare et al. 2017)." In order to confidently differentiate these two species, DNA analysis is needed (see DNA analysis method in Kelt et al. 2023 and Demboski and Sullivan 2003).
References
Demboski JR, Sullivan J. 2003. Extensive mtDNA variation within the yellow-pine chipmunk, Tamias amoenus (Rodentia: Sciuridae), and phylogeographic inferences for northwest North America. Molecular Phylogenetics and Evolution 26:389–408.
Frare CF, Matocq MD, Feldman CR, White AM, Manley PN, Jermstad KD, Hekkala ER. 2017. Landscape disturbance and sporadic hybridization complicate field identification of chipmunks. Journal of Wildlife Management 81:248–258.
Gannon WL, Forbes RB. 1995. Tamias senex. Mammalian species (502):1-6. https://doi.org/10.2307/3504301
Grinnell J, Storer TI. 1924. Animal life in the Yosemite: an account of the mammals, birds, reptiles, and amphibians in a cross-section of the Sierra Nevada. University of California Press, Berkeley, California, USA.
Johnson DH. 1943. Systematic review of the chipmunks (genus Eutamias) of California. University of California Publications in Zoology 48:63–146.
Kelt DA, Coppeto SA, Van Vuren DH, Sullivan J, Wilson JA, Reid N. 2023. Niche conservatism versus niche differentiation in sympatric chipmunks in the northern Sierra Nevada. Journal of Mammalogy 104(5): 979-992.
Sutton D.A. 1995. Problems of taxonomy and distribution in four species of chipmunks. Journal of Mammalogy 76:843–850.
Verts BJ, Carraway LN. 1998. Land mammals of Oregon. Berkeley (CA, USA): University of California Press.