Population Dynamics and Foraging Behavior of Gray Bats in Pittsburg, Ks

Date of Graduation

Fall 2003


Master of Science in Biology



Committee Chair

Lynn Robbins


A colony of gray bats (Myotis grisescens) is presently located within the storm drainage system of Pittsburg, KS. This population has a breeding and non-breeding component, with up to 500 females reproducing in early summer. The mean census compiled by exit count during non-migratory periods for 1999 and 2000 was 2,135.67 and 2,150.91 respectively. A sample of gray bats captured in a harp trap was banded (n=375) on 9 and 10 July 1998. A recapture was performed on 8 August via mist net and 9 August by harp trap. The percent of banded bats recaptured by mist net of 3.73 (15.91% of the total captures) and 1.60 (5.60% of the total captures) in the trap. Juveniles accounted for 19.32% of the captured bats in mist tents and 15.74% in the harp trap. Females were underrepresented when captured by mist net (0.76 : 1) but were overrepresented in the traps (1.46 : 1). In 1999, 138 gray bats were captured in traps and nets. Before June, males were underrepresented in both traps and mist nets (0.14 : 1 and 0.03 : 1 respectively). After June, females were underrepresented in both traps (0.84 : 1) as well as the mist nets (0.92 : 1) with juveniles accounting for 12% of all captures. Fifteen gray bats were tracked during the 2 years; 6 in 1999 and 9 in 2000. Adult males had an average foraging time of 70.95 minutes with a mean greatest distance from roost of 8.65 km. They had an average foraging perimeter of 22.57 km. Adult females had an average foraging time of 53.95 minutes. The mean foraging perimeter was 30.1 km with an average greatest distance from roost of 12.35 km. The mean greatest distance from roost for juvenile males was 3.07 km with mean foraging periods of 15.11 minutes. Juvenile females averaged a foraging perimeter of 21.48 km with a mean greatest distance from roost of 9.64 km and a foraging time of 34.51 minutes. This population and associated habitat should be monitored on an annual basis and human distrubance of the colony must be avoided from 1 April - 30 September.

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© Scott M. Robertson