Went through Guntersville Lock like the pros we are...and then noticed this interesting cave...seems that this is a sanctuary for the endangered gray bat. Protected by a wire fence, 20 to 40 thousand gray bats live there from April to September....This is just one of 12 caves in the Tennessee Valley that appear to be critically important to saving this bat from extinction...glad we passed in the daylight. Can't imagine what all those bats exiting would be like!!!!