Fall and Winter Bat Activity at a Desert Spring in Southern Nevada

Abstract

Bats were captured in a mist net at White Spot Spring, Desert Game Range, Clark County, Nevada during the months September through May for a total of 21 mist net nights. Time of capture, air temperature, and wind conditions are given for each species. Two species, Pipistrellus hesperus and Myotis californicus were active throughout the fall and winter. Pipistrellus was netted at air tempera- tures ranging from 10 to 310 C. Myotis californicus was netted at air temperatures of 20 to 270 C. Approximately 48% of the Myotis were taken at air temperatures be- tween 2o and 60 C. and approximately 11% of the Pipistrellus were netted at air temperatures of 50 C. or below. A third species Antrozous pallidus was netted in low numbers at air temperatures as low as 20 C. Studies of bat activity have usually been conducted during the spring, summer, and early fall months when bat activity is highest. Since bat activity is low or non-existent in temperate areas during the fall and winter, few data on activity are available for these seasons. The present study provides some indications of fall and winter activity for certain species found to be active at these seasons in southern Nevada. DESCRIPTION OF THE STUDY AREA. White Spot Spring is lo- cated at 4460 feet elevation, on the north-facing slope of the Las Vegas Range, Desert Game Range, Clark County, Nevada. The spring flow is contained within a stone tank which is approximately 11.5 feet square by 2 feet deep. The tank was usually full of water. It is bordered on one side by Tamarix spp. and Phragmites communis. The surrounding area consisting or rolling hills is covered by various desert shrubs in- cluding Coleogyne ramosissima, Larrea divaricata, Yucca schidigera, and Atriplex canescens.