Author: Richard Stark

 Location: Delaware and Ottawa Counties, Oklahoma

Participants: Richard Stark, Oklahoma Ecological Services Field Office and Steve Hensley, Ozark Plateau National Wildlife Refuge

Executive summary: Richard Stark of the Oklahoma ES Field Office and Steve Hensley, manager of the Ozark Plateau National Wildlife Refuge, visited January-Stansberry and Boy Scout Caves located in Delaware and Ottawa Counties, Oklahoma, respectively, on October 25, 2007.  Both caves occur on units of the Ozark Plateau National Wildlife Refuge and are used by a maternity colony of the federally-listed endangered gray bat.  The caves were visited to measure the guano piles that have collected underneath the main roost sites during the last maternity season.  Guano pile measurements are taken as a method to obtain an estimate on the colony size.  These efforts allow documentation of population trends and response to recovery efforts.  A colony of gray bats was still present in January-Stansberry Cave about 75 meters beyond the main guano pile.  A colony also was still roosting in Boy Scout Cave over the main guano pile.  Staff quickly and quietly took the guano pile measurement in January-Stansberry Cave without any apparent disturbance to the colony, likely as a result of the distance between the roosting colony and the main guano pile.  Boy Scout Cave was quickly and quietly exited to avoid disturbing the bat colony that was still roosting over the main guano pile.  The Gray Bat Recovery Plan indicates that some gray bats migrate to their hibernacula and enter into hibernation by September, and that nearly all do so by early October.  The discovery of gray bat colonies in these two maternity caves in late October (along with the discovery of a gray bat colony at another maternity cave in Oklahoma on October 19, 2007) illustrates that the break up and migration of maternity colonies in fall is a gradual process for which the exact timing will vary from year to year, possibly as a result of changes in local climatic conditions.  Periods of migration and hibernation likely are highly influenced by changes in temperature, light regime, and food resources.  For example, gray bats that occur in Florida, a more southern and relatively warmer portion of their range, are know to migrate to cooler caves in northern Alabama and Tennessee as late as November or December.  As a precautionary measure, all future trips to gray bat maternity caves in Oklahoma to measure guano piles should be done in mid-November.  Visiting the maternity caves in mid-November should reduce the chance of disturbing bats that may result from unintentionally entering the caves before the bats have migrated to their hibernacula in northern Arkansas and Missouri.  We plan to re-visit Boy Scout Cave in mid-November of 2007.  No signs of recent vandalism at either cave were observed. 

FWS programs involved: Ecological Services and Refuges