April 10, 2009

Yellow-faced Pocket Gopher (Cratogeomys castanops)

Yellow-faced Pocket Gopher (Cratogeomys castanops)
Order Rodentia : Family
Geomyidae : Cratogeomys castanops (Baird)

Yellow-faced Pocket Gopher (Cratogeomys castanops)Description
A moderately large pocket gopher, dull yellowish brown in color, with one deep groove on outer face of each upper incisor; feet blackish (whitish in most other gophers). External measurements average: (males) total length, 295 mm; tail, 95 mm; hind foot, 33 mm; (females) 256-77-33 mm. Weight, (males) 216-321 g; (females) 213-330 g.

Found in western one-third of state, from Panhandle southward to Val Verde County. Isolated populations from Maverick and Cameron counties along the Rio Grande.

These large gophers are partial to deep, mellow soils that are relatively free from rocks. Where the three genera — Cratogeomys, Geomys, and Thomomys — occur in the same general area, as in western Texas, Thomomys usually occupies the shallower, rocky soils in the mountains, Geomys lives in the deep sands along the rivers, and Cratogeomys utilizes the areas in between. However, the sandy areas in which no Geomys occur are likely to be occupied by Cratogeomys. The three genera are usually mutually exclusive in their distribution.

Yellow-faced Pocket Gopher (Cratogeomys castanops)Their burrows are from 75 to 100 mm in diameter, depending on the texture of the soil. The tunnels and mounds are smaller in clayey than in sandy soils. They feed chiefly on roots and stems of vegetation, including the outer bark on the roots of trees. Alfalfa, clover, and garden vegetables are also utilized. Breeding probably begins in March or April. By mid-July nearly full-grown young in juvenile pelage are common. Lactating females have been captured in June and gravid females in early August. Litter size is two.

It appears that conditions of increasing aridity may favor the distribution of Cratogeomys over other gophers, such as Thomomys. From early 1969 to April, 1970, the Davis Mountains of the Trans-Pecos received little or no rain. As the area became drier, Thomomys, which once occurred from near the bed of Limpia Creek to the foot of the rock bluffs lining the canyon, moved closer to the stream and Cratogeomys moved into the vacated area. These changes may be linked to a decrease in soil moisture and subsequent increase in xeric-adapted plants, both conditions which would favor Cratogeomys over Thomomys.

In situations where Cratogeomys and Geomys are sympatric in the Texas Panhandle, Geomys are restricted to the deep sandy soils whereas Cratogeomys tend to occupy shallower, firmer soils. The yellow-faced pocket gopher does quite well in the deeper soils, but is apparently excluded from such sites by the presence of Geomys.

In previous editions the name Pappogeomys castanops was used for this species. Recent genetic studies of the genus Pappogeomys have shown the subgenera Pappogeomys and Cratogeomys of sufficient distinction to warrant the elevation of both to generic status.

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