Direct human disturbance and vandalism is the major factor leading to population decline in gray bats.
During the 1960s, bats were killed for entertainment purposes as they emerged from caves or were caught to be used for pranks.
Many property-owners attempted to exterminate entire colonies due to unsubstantiated fears that the bats may be carrying rabies.
Bats that roost within 100m inside the cave and only 2m above the cave floor are especially prone to vandalism and high-intensity disturbance.
Bats that roost in higher ceilings or further inside the cave are less prone to direct destruction.
One study showed that caves with ceiling heights greater than 15 m above the floor were virtually protected from spelunkers.
Even without direct destruction, human visitation to caves can cause adverse effects on gray bat populations.
Each human entry into a cave causes all bats within range of light or sound to at least partially arouse from hibernation.
Arousal of gray bats while they are hibernating can cause them to use up energy, lowering their energy reserves.
Because these reserves must sustain the bats through hibernation and spring migration, if the bat runs out of reserves, it may leave the cave too soon, decreasing its chances of survival.
Each disturbance during hibernation is estimated to use energy that otherwise could sustain a gray bat through 10–30 days of undisturbed hibernation.
When flightless young are present in June and July, females escaping a predator or other disturbance may drop their young in the panic, leading to increased juvenile mortality.
Direct human disturbance and vandalism is the major factor leading to population decline in gray bats. During the 1960s, bats were killed for entertainment purposes as they emerged from caves or were caught to be used for pranks. Many property-owners attempted to exterminate entire colonies due to unsubstantiated fears that the bats may be carrying rabies. Bats that roost within 100m inside the cave and only 2m above the cave floor are especially prone to vandalism and high-intensity disturbance. Bats that roost in higher ceilings or further inside the cave are less prone to direct destruction. One study showed that caves with ceiling heights greater than 15 m above the floor were virtually protected from spelunkers. Even without direct destruction, human visitation to caves can cause adverse effects on gray bat populations. Each human entry into a cave causes all bats within range of light or sound to at least partially arouse from hibernation. Arousal of gray bats while they are hibernating can cause them to use up energy, lowering their energy reserves. Because these reserves must sustain the bats through hibernation and spring migration, if the bat runs out of reserves, it may leave the cave too soon, decreasing its chances of survival. Each disturbance during hibernation is estimated to use energy that otherwise could sustain a gray bat through 10–30 days of undisturbed hibernation. When flightless young are present in June and July, females escaping a predator or other disturbance may drop their young in the panic, leading to increased juvenile mortality.
Gray bat