As we enter fall, this year’s baby bats are now self-sufficiently volant – weaned from their moms, becoming skillful fliers, capturing insects, and learning about their surroundings. Soon, many bats will move away from their summer roosts, either on their way to cold, stable hibernacula, or to locations with moderate winter temperatures where they can retain some degree of activity on warm nights, opportunistically feeding or drinking water.
This is one of the seasonal periods of bat activity when it is appropriate to conduct “take avoidance measures” prior to disturbance or removal of habitat. These could include humane eviction, partial dismantling (under supervision of a qualified bat biologist), or two-step tree removal (again, under supervision, and instruction). That window will close around October 15 in this region, or when night temperatures drop below 40-45F, and/or when rains set in. After that time, bats that remain in roosts will begin to enter torpor, becoming inactive for days or weeks at a time. Winter months are not acceptable periods to remove or disturb bat habitat.
The next seasonal period of bat activity is about March 1 (weather permitting), until about April 15, when females begin giving birth to pups. Throughout the maternity season, until bats become self-sufficiently volant, it is not safe to remove or disturb bat habitat.
This is also the time when we conduct post-construction monitoring of replacement, enhancement, or existing habitat. Here are a couple of photos of a recent survey of extremely successful day/night bat roost habitat which Greg designed for a new replacement bridge.