Bobcat Canyon, a large secondary canyon on the eastern side of Wetherill Mesa, is a major drainage for much of the mesa at its widest part. The mesa top drains southeast into a pour-off at the head of Bobcat Canyon. A stand of big sagebrush, _Artemisia tridentata_, grows in the sandy soil of the drainage, and extends northwest for several hundred yards from the pour-off. The sagebrush invades the pinyon-juniper forest at the periphery of the area. Two traplines were set in the drainage, with trapping stations at intervals of 25 feet. The lines traversed elevations of 7,000 to 7,100 feet, and were run from June 26 to 29, 1962. Grasses are the most abundant plants in the ground cover. _Artemisia dracunculus_ is common in the drainage, and _A. nova_ grows around the periphery of the drainage. Other species occurring in this stand include: _Aster bigelovii_ _Tetradymia canescens_ _Tragopogon pratensis_ _Bromus tectorum_ _Poa fendleriana_ _Sitanion hystrix_ _Stipa comata_ _Lupinus argenteus_ _Calochortus gunnisonii_ _Sphaeralcea coccinea_ _Phlox hoodii_ _Eriogonum umbellatum_ _Peraphyllum ramosissimum_ _Purshia tridentata_ _Penstemon linarioides_ No mice were caught in three nights of trapping (360 trap nights), and only one mammal, a _Spermophilus variegatus_, was seen. _North of Long House, Wetherill Mesa_ Pinyon-juniper forest with a dominant ground cover of _Poa fendleriana_ was described by Erdman (1962) as one of the three distinct types of pinyon-juniper woodland on Wetherill Mesa. Such a woodland occurs adjacent to the Bobcat Canyon drainage, and is continuous across the Mesa from above Long House to the area near Step House. Plants in the ground cover include: _Cryptantha bakeri_ _Opuntia rhodantha_ _Chrysothamnus depressus_ _Solidago petradoria_ _Koeleria cristata_ _Lupinus argenteus_ _Yucca baccata_ _Phlox hoodii_ _Eriogonum racemosum_ _Eriogonum umbellatum_ _Cordylanthus wrightii_ _Pedicularis centranthera_ _Penstemon linarioides_ _Penstemon strictus_ Two traplines were run from July 9 to 12, 1962, in the area south of the Bobcat Canyon drainage at an elevation of 7,100 feet. No mice were caught in three nights of trapping. Four additional lines were established on July 24, 1962, and were run for three nights, in the area north of the Bobcat Canyon drainage at elevations of 7,100 to 7,150 feet. _P. maniculatus_ and _P. truei_ were caught here (Table 1). This vegetational association may have few rodents because there is a shortage of places where they can hide. Although _Poa fendleriana_ is abundant, the lack of shrubs leaves little protective cover for mammals. _Mug House--Rock Springs_