Last updated: October 3, 2024
Article
Bat Acoustic Monitoring at Glacier Bay National Park and Preserve
noctivagans) is one of the bat species that has been detected acoustically in Glacier Bay.
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What bat species frequent different areas of Glacier Bay National Park and Preserve?
Principal Researchers: Paul Burger (NPS), Tania Lewis (NPS)
Dates: Data collection will be conducted May 2017 —October 2025.
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Introduction
When thinking of animals that echolocate to navigate and detect prey, bats are usually the first to come to mind. By bouncing sound waves off of objects, they are able to locate and hunt insects, as well as detect any objects that may obstruct their path of flight! But echolocation doesn’t just help bats find their dinner— it also helps scientists find bats!
In order to identify and locate bats, researchers use a special kind of equipment called an acoustic bat detector. This is comprised of a microphone and recording device that automatically turns on at dusk, records bat calls, and shuts off in the morning. Some bat calls are loud enough to be heard by the unaided ear, while others can only be heard by an ultrasonic microphone, which is when acoustic detectors are useful. Bat calls are species-specific and vary in frequency range and pattern. Scientists can look at sonograms (visual representations of sound) to determine which bats are in an area.
Acoustic monitoring is a preferred method of data collection since it is automated and equipment is able to be left out for weeks at a time. It is also non-invasive– meaning we don’t have to disturb the bats to collect data, but can simply record their calls as they fly overhead!
Glacier Bay National Park is currently investigating the distribution and diversity of bats in the park, with the help of acoustic bat detectors. Bats are migratory mammals, so understanding their gene flow throughout the United States helps us better protect them from threats such as White-Nose Syndrome, a fungal disease that is negatively impacting bat populations across the country. Additionally, Southeastern Alaska bats in particular are not well studied, so this knowledge also contributes to our understanding of Alaska bats as a whole.
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NPS photo/ S. Elizarraras
Methods
Researchers deploy acoustic bat detectors in Glacier Bay National Park in late Spring and monitor through the Fall. Detectors are deployed in both the front and backcountry of Glacier Bay, and locations will vary slightly depending on the year. All detector sites are selected by their proximity to water, or are placed in an area where there is already documented bat activity. Microphones and recorders are attached to trees (see photo on the right) and set to record starting at dusk and run until dawn. Hobo loggers are also deployed with the detector to track water and temperature. Researchers will periodically maintain the detector setups to replace batteries and ensure everything is running smoothly. At the end of the season, all acoustic data is uploaded for analysis. This is when we determine which hours and months bats are most active, which bats fly through the park, and who frequents an area the most.
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Results
As of 2023, five different species of bat have been confirmed in Glacier Bay National Park through the acoustic monitoring study. These species have been identified as Silver haired bats (Lasionycteris noctivagans), Little brown bats (Myotis lucifugus), Long-legged myotis (Myotis volans), Long-eared myotis (Myotis evotis), and California myotis (Myotis Californicus). All five species were detected in the Glacier Bay backcountry, while four out of the five were confirmed in the Bartlett Cove Developed Area (though the fifth, the long-eared myotis, may be present as well). The highest bat activity in the front country was recorded between the months of July and August, and in the backcountry between August and September. The species most frequently detected acoustically have been Little Brown, Silver haired, and Long-legged Myotis. However, Little Brown bats are the species most commonly seen. Going forward, Glacier Bay hopes to expand this study into more detector locations across the park!