Perognathus parvus (Peale, 1848)

Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Heteromyidae, Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona: Lynx Edicions, pp. 170-233 : 207-208

24.

Columbia Plateau Pocket Mouse

Perognathus parvus

French: Souris-a-abajoues des pinedes / German: Columbia-Plateau-Seidentaschenmaus / Spanish: Ratén de abazones de la Meseta del Columbia

Taxonomy. Cricetodipus parvus Peale, 1848 ,

“Oregon,” USA. Clarified by W. H. Osgood in 1900 as “assumed to be The Dalles, [Wasco Co.,] Oreg.”

Based on detailed sequencing of nDNA and mtDNA genes, P. parvus is a member of the parvus species group ofsilky pocket mice, along with P. alticola and P. mollipilosus , and is basal to the other two, closely related (and possibly conspecific) species. Recent genetic studies revealed that P. mollipilosusis specifically distinct from P. parvus ; the two diverged an estimated eleven million years ago. The two species are known to co-occur at only one locality in northcentral Oregon. The species identity of subspecies on the central and eastern Snake River Plain (clarus and idahoensis) and north into south-western Montana is not yet fully established. They are included within P. mollipilosus here based on the karyotype of a population of clarus in north-eastern Utah and sequence data for a population of clarus in south-eastern Wyoming. It is equally possible that populations of the Snake River Plain and north into Montana (including the northern two-thirds of clarus) belong to P. parvus . It was considered conspecific with P. mollipilosus until 2014. Five subspecies recognized.

Subspecies and Distribution.

P.p.parvusPeale,1848—NWUSA(SEWashingtonandC&SEOregontoSWIdahoandtoNWNevada).

P.p.columbianusMerriam,1894—-NWUSA(ColumbiaPlateauofCWashington).

P.p.laingiE.M.Anderson,1932—SWCanada(upperOkanaganBasinofSCBritishColumbia).

P.p.lordiGray,1868—SWCanadaandNWUSA(SCBritishColumbia,NC&EWashington,andadjacentNWIdaho).

P. p. yakimensis Broadbooks, 1954 — NW USA (SC Washington).

Descriptive notes. There are no specific measurements available. Pelage of the Columbia Plateau Pocket Mouse is soft, fine, and full, with no hint of spines or stiff bristles; posterior one-half of sole of hindfoot has a sparse covering of short hairs; and tail is short and not tufted. Unlike most other silky pocket mice, the Columbia Plateau Pocket Mouse has lobed antitragus of ear pinna, and tail is slightly crested for distal one-third (with dark hairs). It is large-sized for the genus. Hairs on inner surfaces of ear pinna are white or yellowish. Dorsal pelage is ocherous buff, overlain with blackish hair; lateral line usually is faintly expressed; and under parts are white. Tail is same length or slightly longer than head-body length and bicolored. Chromosomal complement has 2n = 54 and FN = 104. Compared with the geographically nearest species, the Little Pocket Mouse ( P. longimembris ), the Columbia Plateau Pocket Mouse is distinguished by its much largersize, lobed antitragus, and longer, darker hairs forming slight crest on distal part oftail. In most of its distribution, the Columbia Plateau Pocket Mouse is the only heteromyid rodent; in the southern parts of its distribution, it encounters Ord’s Kangaroo Rat ( Dipodomys ordii ), the Dark Kangaroo Mouse ( Microdipodops megacephalus ), and the Little Pocket Mouse.

Habitat. Primarily sagebrush ( Artemisia , Asteraceae ) steppe in arid or semiarid situations on more or less sandy ground and shrub-steppe habitat of open pinyon ( Pinus , Pinaceae )—juniper ( Juniperus , Cupressaceae ) woodland. Distribution of the Columbia Plateau Pocket Mouse centers on the Columbia Plateau, including an extension into southern British Columbia, but in eastern Oregon and south-western Idaho,it extends through the Blue Mountains onto the Snake River Plains and may extend across southern Idaho and north into south-western Montana (populations provisionally assigned here to the Great Basin Pocket Mouse). Burrows typically are constructed at bases of shrubs and include permanent burrow with nest chamber and more simple escape or refuge burrows with multiple entrances. Entrance to permanent burrow is plugged during the day.

Food and Feeding. Diet of the Columbia Plateau Pocket Mouse consists largely of seeds of shrubs, annuals, and grasses, but it also includes smaller amounts of green vegetation and insects; insects are eaten more commonly in the spring before grass seeds ripen. Food items are collected in external, fur-lined cheek pouches and transported back to burrows, where they are stored in burrow caches. As in other heteromyids, volume of seeds jammed into cheek pouchesis equivalent to daily energy requirement. The Columbia Plateau Pocket Mouse does not need to drink water, subsisting entirely on water from its food and water produced as a byproduct of metabolism.

Breeding. Breeding season of the Columbia Plateau Pocket Mouse begins in April-May and extends into autumn. Females have 1-2 litters/year, rarely three, except in dry years when one or nolitters are produced. Number oflitters is correlated closely with precipitation and production of winter annuals. If precipitation is adequate, juveniles born early in the breeding season may producea litter in the autumn of the same year. Gestation is 21-28 days, and mean litter sizes are 4-5 young (range 2-8).

Activity patterns. The Columbia Plateau Pocket Mouse is nocturnal and terrestrial, and like other species in the genus,it enters torpor for various periods in all seasons, particularly winter. Torpor may result from cold temperatures or low foraging success. During longer periods of winter torpor, individuals wake periodically to eat from seed caches.

Movements, Home range and Social organization. The Columbia Plateau Pocket Mouse appears to be asocial. Estimates of home range sizes vary widely (0-01-4 ha), but male home ranges appear to be larger than those of females. Studies disagree on the extent of overlapping of home ranges. Density averages 28-5 ind/ha, but it may be greater than 80 ind/ha during years with above average precipitation. The Columbia Plateau Pocket Mouse frequently is numerically dominant in small mammal communities.

Status and Conservation. Classified as [Least Concern on The IUCN Red Lust.

Bibliography. Aquino & Neiswenter (2014), Kirkland (1999), Linzey & NatureServe (Hammerson) (2008l), Osgood (1900), Riddle et al. (2014), Verts & Kirkland (1988), Williams (1978a), Williams et al. (1993).

Figures

1. Salvin’s Spiny Pocket Mouse (Heteromys salvini), 2. Panamanian Spiny Pocket Mouse (Heteromys adspersus), 3. Mexican Spiny Pocket Mouse (Heteromys irroratus), 4. Jaliscan Spiny Pocket Mouse (Heteromys spectabilis), 5. Painted Spiny Pocket Mouse (Heteromys pictus), 6. Nelson's Spiny Pocket Mouse (Heteromys nelsoni), 7. Trinidad Spiny Pocket Mouse (Heteromys anomalus), 8. Overlook Spiny Pocket Mouse (Heteromys catopterius), 9. Paraguana Spiny Pocket Mouse (Heteromys oasicus), 10. Southern Spiny Pocket Mouse (Heteromys australis), 11. Ecuadorean Spiny Pocket Mouse (Heteromys teleus), 12. Gaumer’s Spiny Pocket Mouse (Heteromys gaumeri), 13. Desmarest’s Spiny Pocket Mouse (Heteromys desmarestianus), 14. Goldman’s Spiny Pocket Mouse (Heteromys goldmani), 15. Cloud-dwelling Spiny Pocket Mouse (Heteromys nubicolens), 16. Mountain Spiny Pocket Mouse (Heteromys oresterus)

Subspecies and Distribution. P.p.parvusPeale,1848—NWUSA(SEWashingtonandC&SEOregontoSWIdahoandtoNWNevada). P.p.columbianusMerriam,1894—-NWUSA(ColumbiaPlateauofCWashington). P.p.laingiE.M.Anderson,1932—SWCanada(upperOkanaganBasinofSCBritishColumbia). P.p.lordiGray,1868—SWCanadaandNWUSA(SCBritishColumbia,NC&EWashington,andadjacentNWIdaho). P. p. yakimensis Broadbooks, 1954 — NW USA (SC Washington).