Scope and method of study. My objectives were to record microhabitat and population characteristics of big brown bats (Eptesicus fuscus) inhabiting crevices inside the Keystone Dam, Sand Springs, Oklahoma, determine if any species other than E. fuscus inhabit the dam, identify times of the year that bats are in residence in the dam, and determine if the dam is used as a maternity roost. I recorded microhabitat on five of the nine crevices weekly from April to November 2005 and 2006. Population size was estimated using standard mark recapture and banding techniques monthly from April to November 2005 and 2006. Emergence counts were conducted from May to August 2005. I tried to document movement of bats within the dam using mark recapture and powder tracking.

Findings and conclusions. Only E. fuscus was observed or collected at the dam. Over 40% of bats counted during emergence counts came from crevices 8 and 9 (n = 1405) from May to August 2005. Fewer bats were collected during Season A (May and June) than Season B (July and August) as a result young of the year becoming volant. More bats were counted on the south end and east side of the dam than any other location. Crevice depth and width were statistically different in a north-south direction, suggesting that depth and width may be a limiting factor for bat abundance. Microhabitat characteristics differed statistically for temperature, relative humidity, and wind velocity. All variables, except wind velocity were higher on the west side of the dam. Bats avoided the west side of the dam. A new application for powder tracking for bats was attempted but failed to produce data on bat movement within the dam.