Perognathus amplus, Osgood, 1900

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 : 204

19.

Arizona Pocket Mouse

Perognathus amplus

French: Souris-a-abajoues d’Arizona / German: Arizona-Seidentaschenmaus / Spanish: Raton de abazones de Arizona

Taxonomy. Perognathus amplus Osgood, 1900 ,

Fort Verde, Yavapai Co., Arizona, USA.

Based on detailed sequencing of nDNA and mtDNA genes, P. amplus is a member of the longimembris species group of silky pocket mice along with P. longimembris and P. inornatus . Where P. amplus is sympatric with P. longimembris in west-central Arizona, P. amplus is clearly larger. In the north, where they occur on opposite sides of the Colorado River, they are difficult to distinguish morphologically; however, chromosomal and mitochondrial studies support full specific status of the two. Four subspecies recognized.

Subspecies and Distribution.

P. a. amplusOsgood, 1900 — SWUSAandNWMexico (C & SWArizona, NWSonora).

P. a. cinerisBenson, 1933 — SWUSA (NCArizona).

P. a. pergracilisGoldman, 1932 — SWUSA (NWArizona).

P. a. taylori Goldman, 1932 — SW USA and NW Mexico (SC Arizona, NW Sonora).

Descriptive notes. Head-body mean 71 mm, tail mean 83 mm, ear mean 7 mm, hindfoot mean 21 mm; weight 9-14 g. There is no significant secondary sexual dimorphism. Pelage of the Arizona Pocket Mouse is soft and fine, with no hint of spines or stuff bristles; posterior one-half of sole of hindfoot has a sparse covering of short hairs; and tail is short and nottufted. It has short, rounded ears without a lobed antitragus. The Arizona Pocket Mouse is medium-sized for the genus. Dorsal pelage is orangish tan and sprinkled with blackish hairs, there is a light-colored post-auricular spot that is not particularly conspicuous, and under parts are white or pale tan. Some populations on lava substrates (fine, dark cinder soil) are nearly black. Tail is longer than head-body length and moderately bicolored. Chromosomal complement has 2n = 56 and FN = 84-94. FN = 86 karyotypeis the most widespread, and there is a general trend from FN = 86 in central Arizona to FN = 94 in southern Arizona.

Habitat. Fine-textured, firm soils in desert scrub of the Sonoran Desert, edging into the Mojave and Great Basin deserts. This includes a wide variety of desert shrubs, including greasewood ( Sarcobatus , Sarcobataceae ), rabbitbrush ( Chrysothamnus , Asteraceae ), creosote bush ( Larrea , Zygophyllaceae ), snakeweed ( Gutierrezia , Asteraceae ), and mesquite ( Prosopis , Fabaceae ). The Arizona Pocket Mouse is most common in flat terrain with scattered small shrubs or bunchgrasses.

Food and Feeding. The Arizona Pocket Mouse feeds largely on seeds of shrubs, annuals, and grasses, butit also includes smaller amounts of green vegetation and insects in its diet. Food itemsare collected in external, fur-lined cheek pouches and transported back to burrows, where they are stored in burrow caches.It prefers to forage in small openings between shrubs. Individuals appearto dig about randomly in the soil, are unable to detect seeds buried in the sand more than 2'5 cm, and tend to find more single and random seeds and fewer groups or packets of seeds. Like all small silky pocket mice, the Arizona Pocket Mouse tends to husk seeds or separate seeds from seed heads before stuffing them into cheek pouches. It 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 Arizona Pocket Mouse begins in February-March, soon after females emerge from winter inactivity in burrows; males emerge earlier. Average litter size is 3-5 young (range 1-7), and juveniles appear in May-June, so that populations peak in late summer. There appears to be only one breeding season.

Activity patterns. The Arizona Pocket Mouse is nocturnal and terrestrial, and it enters torpor in winter. Individuals are inactive aboveground in winter but arouse from time to time to eat stored seeds from caches. At one site in south-central Arizona, Arizona Pocket Mice were not trapped in November-March. When in burrows, body temperature cools and metabolic rate slows, perhaps accounting for the surprisingly long life (up to ten years in captivity) for such a small mammal.

Movements, Home range and Social organization. Summer densities of Arizona Pocket Mice fluctuate considerably from year to year, depending on precipitation during the previous winter. This suggests that food limits populations,either by limiting number of young that females can produce, determining survival probability, or both.

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

Bibliography. Aquino & Neiswenter (2014), Best (1993a), Hoffmeister (1986), Linzey, Timm, Alvarez-Castaneda, Castro-Arellano & Lacher (2008d), McKnight (1995, 2005), McKnight & Lee (1992), Price (1999a), 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. a. amplusOsgood, 1900 — SWUSAandNWMexico (C & SWArizona, NWSonora). P. a. cinerisBenson, 1933 — SWUSA (NCArizona). P. a. pergracilisGoldman, 1932 — SWUSA (NWArizona). P. a. taylori Goldman, 1932 — SW USA and NW Mexico (SC Arizona, NW Sonora).