Bat Surveys

A park scientist examining a bat inside a cave passage.

NPS Photo

Mammoth Cave National Park has between 400 to 500 caves and is home to 13 species of bats, some of which are listed as threatened or endangered. Bat monitoring is done year round to track the health and diversity of the park’s bat species.

How does the park study bats?

Through the use of multiple techniques to monitor bats, the park has a better overall picture of the health of its bat population. During the summer months researchers and park interns conduct exit counts outside cave entrances to get estimates of the bat populations using the caves. With the use of night vision technologies such as infrared lighting, night vision goggles, infrared and thermal imaging video cameras, researchers can count bats as they leave the caves or structures at dusk to feed on insects. The staff use the various technologies repeated over several nights to ensure accuracy of the counts.

 

A bat researcher handles a bat that was captured in order to record measurements.

NPS Photo

Researchers also utilize mist netting for some surveys. Small opening mesh nets are placed along known flight corridors and drinking areas to physically capture bats. This allows researchers to check for species diversity, gender percentages and overall health of the bat population. The ability to have bats in hand also allows the researchers to collect hair or tissue samples for genetic or disease testing. These bats may also have small transmitters affixed to them in order to track them to their roosting areas. Several new maternity sites have been discovered this way.

One of the least invasive ways we monitor bats is through the use of acoustic monitoring devices. During the summer season, three driving routes along park roadways are followed for bat acoustic monitoring. Researchers drive at 20 mph for one to two hours along these routes with a sensitive microphone attached to the roof of their vehicle. This microphone is attached to an acoustic detector that records bat calls as the route is driven. The recordings are later analyzed and the bat calls can be displayed and identified.

Winter however poses another challenge as bats are no longer flying outside each night to feed. Instead researchers must enter hibernation sites to do manual counts and take pictures of the roosting bats. Some of these caves have between 1,000 and 350,000 bats to count. Pictures are taken of bat clusters that represent low density, medium density and high density groupings of bats. This allows researchers to obtain count estimates for caves with extremely high numbers of bats. Researchers try to get high quality pictures of each cluster so the bat can be accurately counted.

 

A group of hibernating Indiana Bats.

NPS Photo

What have the surveys taught us?

Since the arrival of White-nose Syndrome (WNS) in the park around 2012, researchers have seen a large decline in numbers of some of the most visible species of bats, such as the federally threatened northern long-eared bat. This is an indication that their numbers have decreased to the point that they are no longer viable on the landscape. What does that mean? It means that their numbers have gotten so low the benefits they once provided are essentially no longer there. However, as some bat species numbers have dipped to all time lows, other species that were once rarely noticed, such as tree-roosting bats like evening bats, have seen their numbers rise, possibly filling the niche left behind.

The ongoing research on bats has allowed the park to be at the forefront of research associated with the fungus that causes WNS. Learning how to slow the spread of the deadly fungus that causes this disease is important to maintain a healthy environment because bats are such an important part of our ecosystem. WNS protocols and management techniques are tested at Mammoth Cave in hopes of helping other parks and private caves in the west to better manage their own sites and hopefully lessen bat mortality associated with the disease.

 

Do your part in protecting the bats of Mammoth Cave National Park!

• Do not enter cave sites in the park that are not part of the guided tour areas. Entry into these sites can disturb bats during hibernation and maternity causing potential loss of bats. 

• It is illegal to enter any cave or rock shelter in the park without prior approval from the park. 

• Make sure as you exit cave tours, to walk across the decontamination mats provided to clean your shoes and lessen the likelihood of spreading WNS to other sites around the world.  

• Educate yourself on bats, the benefits bats provide, and the struggles they face. 

 

Learn More

White-nose Syndrome Response Team What is White-nose Syndrome