Subspeciation in the Kangaroo Rat, Dipodomys ordii / KU. Vol 1 No 23

by Henry W. Setzer

From Dipodomys ordii montanus, D. o. ordii differs in: Size smaller; color lighter; skull narrower across bullae and rostrum; wider interorbitally; all other measurements taken the same, thus imparting to the skull, in dorsal view, a longer, narrower appearance.

From Dipodomys ordii chapmani, D. o. ordii differs in: Size smaller; color lighter; skull smaller; zygomatic arches narrower at suture of jugal and zygomatic process of maxillary; rostrum narrower; upper incisors smaller; nasals shorter; least interorbital width less.

For comparisons with Dipodomys ordii sennetti and Dipodomys ordii compactus see accounts of those subspecies.

Remarks.—Intergradation occurs with Dipodomys ordii chapmani, Dipodomys ordii longipes, Dipodomys ordii medius and Dipodomys ordii attenuatus. Only along the Rio Grande near El Paso, Texas, are individuals of a population uniform. On the periphery of the range, specimens from a given locality may resemble D. o. ordii or D. o. longipes or may be intermediate between these two subspecies.

Animals from the Organ Mountains near Globe Springs, 20 miles north of Cliff, New Mexico, and those labeled with reference to Van Horn, Texas, on the average are darker, have a wider expanse across the auditory bullae, a wider interorbital region and, in most specimens, more distally flared nasals than the norm of other populations. This deviation from the normal is interpreted not as intergradation with any other subspecies but rather as individual variation in a given population.

Specimens from 40 miles southeast of Corona and 10 miles northeast of Socorro, New Mexico, show intergradation between D. o. ordii and D. o. montanus in size of body, configuration of nasals and cranial size. For a discussion of intergradation with D. o. longipes, D. o. medius and D. o. chapmani see the remarks in the accounts of those subspecies.

Specimens from Cananea and Santa Cruz, Sonora, Casas Grandes Viejo, Chihuahua City and Colonia Diaz, Chihuahua, are not typical of D. o. ordii but rather show the influence of some race probably to the southeast that is as yet unknown. In a series of nine specimens from near Casas Grandes Viejo, Chihuahua, four individuals are typically D. o. ordii, four resemble an apparently undescribed form and one specimen is intermediate between D. o. ordii and the unnamed subspecies. This unnamed race differs from D. o. ordii in having darker pelage, darker dorsal stripe on tail, larger body, wider interorbital region, longer skull, greater breadth across the bullae, less vaulted braincase, more robust zygomatic arches and the foramen magnum more deeply notched on both the dorsal and ventral rims. It seems that these animals mentioned above should be referred to D. o. ordii at least until such time as material becomes available from eastern Chihuahua, northern Coahuila and northeastern Durango.

Specimens examined.—Total, 451, distributed as follows:

Arizona: Gila County: Rice, 2 (USBS). Maricopa County: Marinette, 8 (CAS). Pinal County: Oracle, 4 (USBS). Graham County: 20 mi. NE Calva, 5 (USBS); Fort Grant, 11 (7 USBS; 4 MVZ). Pima County: Ft. Lowell, 3 (DRD); 11-1/2 mi. S Tucson, 1 (MVZ); Continental, 20 (8 USBS; 12 DRD); La Osa, 11 (USNM); Babiquivari Mountains 10 mi. N International Boundary, 1 (DRD). Santa Cruz County: 2 mi. S Tumacacori Mission, 1 (DRD); 7 mi. N Patagonia, 4500 ft., 12 (CAS); 3 mi. N Patagonia, 1 (CAS); Calabasas, 7 (6 USBS; 1 USNM). Cochise County: 8 mi. W Bowie, 1 (LACM); Wilcox, 4163 ft., 25 (12 USBS; 5 UM; 4 MVZ; 4 USNM); 12 mi. SE Dos Cabezos, 2 (UM); 1 mi. WSW Chiricahua National Monument, 5000 ft., 1 (MVZ); Portal, 4500 ft., 2 (USBS); Fairbank, 8 (3 AMNH; 5 CNHM); Mouth Pinery Canyon, 4 (USBS).

New Mexico: Torrance County: Gran Quivira, Mesa Jumanes, 6 (USBS). Catron County: Mangos Valley, 3 (USBS); Alma, 3 (USBS); Pleasanton, 7 (USBS). Socorro County: Gallina Mountains, 1 (USBS); 10 mi. NE Socorro, 2 (USBS); 3 mi. N Socorro, 3 (MVZ); Socerro, 1 (USBS); Range, 2 mi. SW Socerro, 4700 ft., 2 (MVZ); Lava Mesa; S Clyde, 4300 ft., 1 (MVZ); Dry Creek, 3 (USBS); San Augustine Plain, 12 mi. N Monica Springs, 2 (USBS). Lincoln County: Guyo Canyon, 40 mi. SE Corona, 1 (USBS); 4 mi. W Carrizozo, 2 (UM). Grant County: Gila, 5 (USBS); Cactus Flat, 20 mi. N Cliff, 3 (USBS); Cliff, Gila River, 4470 ft., 1 (USBS); Silver City, 2 (USBS); Redrock, 2 (USBS); 9 mi. N Faywood, 2 (USBS); Hachita, 1 (USBS); Dog Spring, 11 (USNM); Deer Creek, Culberson Ranch, 2 (USBS). Sierra County: Fairview, 6500 ft., 1 (USBS); Cuchillo, 4700 ft., 3 (USBS); Lake Valley, 5000 ft., 3 (USBS). Otero County: Tularosa, 5 (USBS); 10 mi. SW Tularosa, 2 (CNHM); Quartz Sands, SW Tularosa, 2 (MVZ); White Sands, 12 mi. W Alamogordo, 1 (MVZ); 2 mi. S Alamogordo, 2 (UM); 3 mi. S Alamogordo, 1 (UM); 5 mi. S Alamogordo, 1 (UM); 9 mi. SW Alamogordo, 1 (UM); 12 mi. SW Alamogordo, 2 (UM); 15 mi. SW Alamogordo, 1 (LACM); White Sands, 18 mi. SW Alamogordo, 7 (MVZ); 19 mi. SW Alamogordo, 3 (UM); White Sands National Monument, 24 (13 CNHM; 11 LACM); 1/2 mi. SW Escondido, 4000 ft., 2 (MVZ); Jarilla, 1 (USBS). Hidalgo County: 10 mi. NW Lordsburg, 6 (LACM); 4 mi. NW San Luis Pass, 5200 ft., Animas Valley, 5 (MVZ). Luna County: Deming, 11 (USBS). Dona Ana County: Garfield, 4 (USBS); 6 to 8 mi. NE Las Cruces, 1 (CAS); 15 mi. W Las Cruces, 1 (LACM); 11 mi. W Las Cruces, 2 (CAS); Las Cruces, 3 (USBS); Organ Mountains, near Globe Springs, 2 (USBS); Coe's Ranch, El Paso Road, 35 mi. N El Paso, Texas, 2 (USBS); 1/4 mi. N Strauss, 2 (CAS); 1 mi. E Strauss, 4100 ft., 7 (MVZ); 35 mi. W El Paso, Texas, 2 (USNM); 20 mi. W El Paso, Texas, 1 (USNM); 10 mi. W El Paso, Texas, 1 (USNM); Mexican Boundary, near monument 5, Lat. 31° 47'; Long. 30° 15', 13 (USNM). Eddy County: 3 mi. NW Carlsbad, 7 (MVZ); 2 mi. E Carlsbad, 1 (KU); Eddy, 10 (USBS).