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Bat Monitoring at Tory’s Cave Preserve in New Milford

Why is Tory’s Cave closed?

Tory’s Cave is closed to protect the rare and endangered bats that depend on its habitat for survival. In 2017, NCLC installed a protective gate across the cave’s opening to prevent the unintentional introduction of Pseudogymnoascus destructans, the fungus that causes White-nose Syndrome. White-nose syndrome (WNS) is a devastating disease that causes hibernating bats to burn through their stores of body fat, killing them, or causing them to wake from hibernation in the winter. If awoken in the winter, the bats often succumb to the cold while trying to find food that is not present at that time of year. Click here to watch a video about WNS.

How do you determine the presence of bats?

NCLC partners with biologists at the Connecticut Department of Energy and Environmental Protect (CT DEEP) to record audio of bat vocalizations. This is called acoustic monitoring.  The biologists analyze the recordings and identify the species and approximate number of bats. The monitoring is conducted in the spring, as bats are emerging from hibernation, and in the fall as bats move into hibernation.

What did the recordings find?

This year the recordings confirmed the presence of a Little brown bat, Myotis lucifugus.  State biologist Brian Hess reports, “This is a notable recording of a rare species. Little brown bats used to be quite common, but they are now rare and on our endangered list.  They have lost between 90-95% of their population by our best guess, and we only have a couple remaining known maternity colonies in the state.”  That devastating population decline began in  2008 when the fungus and White-nose Syndrome arrived in Connecticut.

Why did the acoustic monitoring find fewer bats this year?

CT DEEP has conducted acoustic monitoring at Tory’s Cave since 2016. Prior year surveys have documented the presence of big brown bats, little brown bats, red bats, and hoary bats. The 2020 fall acoustic monitoring recorded one little brown bat. It is possible the unusual weather in 2020 affected the number of bats present.

This fall was unusually warm and dry. Weather plays an important role in the fall movement of bats into their winter shelters, called hibernacula.  DEEP biologist Brian Hess speculated the warm fall may explain why only one bat was recorded stating, “Bats may not have settled into their winter spots yet. Late September and early October is usually the right time for some species, but it is highly variable.”  It will be interesting to see if the spring acoustic monitoring captures other species of bats who moved into the cave later.

Why protect bats and their habitat?

Bats are amazing animals. For farmers they perform the equivalent of $1 billion dollars of pest control every year by eating insects.  Some species of bats feed on nectar and pollen and are important pollinators.  For example, bats are the most important pollinator for the agave plant, a common sweetener and key ingredient in tequila. In rainforests, fruit eating bats disperse seeds.

Bats are also wild animals that may carry diseases harmful to humans. That is why you should never touch a bat. As habitat for bats is lost, bats and humans come into contact more regularly. Protecting sufficient land for habitat helps to keep these amazing animals, and the humans that depend on them, safe.

With WNS decimating bat populations across the United States, every bat is precious and many species that used to number in the millions are in danger of extinction. Can you imagine a summer night without the graceful dips and dives of bats eating mosquitos? A world without bats would be a difficult place for farmers, forests, and night-blooming plants to thrive.