Baiomys musculus (Merriam, 1892)

Don E. Wilson, Russell A. Mittermeier & Thomas E. Lacher, Jr, 2017, Cricetidae, Handbook of the Mammals of the World – Volume 7 Rodents II, Barcelona: Lynx Edicions, pp. 204-535 : 365

209.

Southern Pygmy Mouse

Baiomys musculus

French: Baiomys austral / German: Stdliche Amerikanische Zwergmaus / Spanish: Ratén pigmeo meridional

Taxonomy. Sitomys musculus Merriam, 1892 , Colima, Colima, Mexico.

Genetic subdivision of B. musculus was reported corresponding to coastal regions of Michoacan, and two species could be represented, suggesting additional studies are necessary. Eight subspecies are recognized.

Subspecies and Distribution.

B.m.musculusMerriam,1892—SNayarit,W&CJalisco,Colima,andMichoacan states(WCMexico).

B. m. brunneus J. A. Allen & F. M. Chapman, 1897 — SE Puebla and C Veracruz states (EC Mexico).

B.m.grisescensGoldman,1932—fromSCGuatemalaSEtoSWHonduras.

B.m.handleyiPackard,1958—knownonlyfromthetypelocalityinWGuatemala.

B.m.infernatisHooper,1952—SCPueblaandNOaxacastates(CMexico).

B.m.nigrescensOsgood,1904—ChiapasState(SMexico),SGuatemala,andElSalvador.

B.m.pallidusRussell,1952—Guerrero,Morelos,SWPuebla,andOaxacastates(SWMexico).

B. m. pullus Packard, 1958 — NW edge of Nicaragua.

Descriptive notes. Head-body 65-79 mm, tail 35-56 mm, ear 9-12 mm, hindfoot 14-17 mm; weight 6-10 g. The Southern Pygmy Mouse is one of the smallest mice in North America. It can be distinguished from the Northern Pygmy Mouse ( B. taylor ) by size of hindfoot (16 mm or more) and size of baculum (3-3-9 mm), which is larger in the Northern Pygmy Mouse. Dorsum is brown-red to dark brown, and venteris pale or white.

Habitat. Tropical deciduous forests, thorn forests, xeric scrublands, coastal dunes, pastures, and croplands from sea level to elevations of 2000 m. Southern Pygmy Mice inhabit tropical and semi-tropical areas where grasses and shrubs provide sufficient cover; they are also found in abandoned fields and along edges of sugar cane plantations and coconut palms. Where they coexist, the Southern Pygmy Mouse prefers tropical lowlands, and the Northern Pygmy Mouse is most common in temperate highlands.

Food and Feeding. Southern Pygmy Mice feed mainly on herbs and fresh grasses but also seeds and small insects.

Breeding. Southern Pygmy Mice reproduce throughout the year, with less activity in winter and spring. Gestation lasts 20-25 days, lactation averages 20 days, and litters have 1-5 young (average three).

Activity patterns. Southern Pygmy Mice are diurnal and crepuscular.

Movements, Home range and Social organization. Home ranges can be 30 m in diameter, and densities are 15-20 ind/ha. Southern Pygmy Mice construct their nests with grass remnants in underground burrows between rocks or at bases of bunch grasses.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Southern Pygmy Mice are abundant in croplands and pastures and face no known conservation threats.

Bibliography. Allen & Chapman (1897a), Ceballos & Miranda (1986, 2000), Chavez & Espinosa (2014b), Eshelman & Cameron (1987), Goldman (1932b), Hooper (1952b), Merriam (1892b), Osgood (1904), Packard (1960), Packard & Montgomery (1978), Russell (1952a).

Figures

208. Golden Mouse (Ochrotomys nuttalli), 209. Southern Pygmy Mouse (Baiomys musculus), 210. Northern Pygmy Mouse (Baiomys taylori), 211. Short-tailed Singing Mouse (Scotinomys teguina), 212. Long-tailed Singing Mouse (Scotinomys xerampelinus), 213. Yellow Deermouse (Isthmomys flavidus), 214. Mount Pirr 1 Deermouse (Isthmomys pirrensis), 215. Florida Deermouse (Podomys floridanus), 216. Volcano Deermouse (Neotomodon alstoni), 217. Short-nosed Harvest Mouse (Reithrodontomys brevirostris), 218. Darien Harvest Mouse (Reithrodontomys darienensis), 219. Slender Harvest Mouse (Reithrodontomys gracilis), 220. Mexican Harvest Mouse (Reithrodontomys mexicanus), 221. Nicaraguan Harvest Mouse (Reithrodontomys paradoxus), 222. Cozumel Harvest Mouse (Reithrodontomys spectabilis), 223. Talamancan Harvest Mouse (Reithrodontomys creper), 224. Rodriguez's Harvest Mouse (Reithrodontomys rodriguez), 225. Narrow-nosed Harvest Mouse (Reithrodontomys tenuirostris), 226. Small-toothed Harvest Mouse (Reithrodontomys microdon), 227. Costa Rican Harvest Mouse (Reithrodontomys cherrii), 228. Chiriquian Harvest Mouse (Reithrodontomys garichensis), 229. Musser’s Harvest Mouse (Reithrodontomys musser), 230. Baker’s Harvest Mouse (Reithrodontomys baker), 231. Fulvous Harvest Mouse (Reithrodontomys fulvescens), 232. Hairy Harvest Mouse (Reithrodontomys hirsutus), 233. Sonoran Harvest Mouse (Reithrodontomys burt), 234. Volcano Harvest Mouse (Reithrodontomys chrysopsis), 235. Eastern Harvest Mouse (Reithrodontomys humulis), 236. Western Harvest Mouse (Reithrodontomys megalotis), 237. Plains Harvest Mouse (Reithrodontomys montanus), 238. Salt-marsh Harvest Mouse (Reithrodontomys raviventris), 239. Sumichrast’s Harvest Mouse (Reithrodontomys sumichrasti), 240. Zacatecan Harvest Mouse (Reithrodontomys zacatecae), 242. Northern Grasshopper Mouse (Onychomys leucogaster), 243. Southern Grasshopper Mouse (Onychomys torridus), 244. Osgood’s Deermouse (Osgoodomys banderanus)

Subspecies and Distribution. B.m.musculusMerriam,1892—SNayarit,W&CJalisco,Colima,andMichoacan states(WCMexico). B. m. brunneus J. A. Allen & F. M. Chapman, 1897 — SE Puebla and C Veracruz states (EC Mexico). B.m.grisescensGoldman,1932—fromSCGuatemalaSEtoSWHonduras. B.m.handleyiPackard,1958—knownonlyfromthetypelocalityinWGuatemala. B.m.infernatisHooper,1952—SCPueblaandNOaxacastates(CMexico). B.m.nigrescensOsgood,1904—ChiapasState(SMexico),SGuatemala,andElSalvador. B.m.pallidusRussell,1952—Guerrero,Morelos,SWPuebla,andOaxacastates(SWMexico). B. m. pullus Packard, 1958 — NW edge of Nicaragua.