Why Traditional Cave Survey Arouses WNS-Affected Colonies

Each arousal costs a torpid bat roughly 108 mg of fat — the equivalent of 68 days of normal torpor — and WNS-infected bats already arouse three to four times more often than healthy ones. Traditional cave survey compounds a mortality problem the surveyor is trying to solve.

A 2019 winter count in an 18,000-bat Myotis lucifugus hibernaculum in upstate New York used a three-person team moving at 0.5 m/s along the main passage with red-filtered headlamps, standard practice under most state DNR bat-survey protocols. Post-hoc analysis of acoustic monitors left inside the chamber showed that 23% of the cluster aroused within 40 minutes of the team passing beneath, and arousal cascades continued for another six hours after the team left. Extrapolated against the ~108 mg of fat consumed per arousal, the survey effectively burned 450 kg of aggregate winter fat stores from one three-hour visit. In a colony already losing individuals to WNS, that is the difference between April emergence and mid-winter starvation.