One Treatment Does Not Fit All Sizes

Forest management practices and bat habitat

two people stand in a forest collecting data about bat habitat
Leanne Burns and a colleague set up a bat detector. Burns is a researcher at Clemson University and senior author of the Forest Ecology and Management paper. USDA Forest Service photo by Susan Loeb.

Bats are important components of healthy forests and provide critical ecological services across numerous different ecosystems. For decades, bat populations throughout the southern U.S. have been declining due to habitat disturbance and loss.

USDA Forest Service scientist Susan Loeb contributed to two recent publications to address this issue, suggesting ways to improve bat management practices across the South. The first, published in the journal Forest Ecology and Management, studied the effects of fire and severity on the occupancy of bats in mixed pine-oak forests. The second, published in the Journal of Mammalogy, involved a qualitative synthesis of temperate bat responses to silvicultural treatments.

Loeb has been a research ecologist with the Southern Research Station for 33 years. Her work initially began with squirrels, but she now focuses on bat research in four distinct areas:

  1. threatened and endangered species,
  2. forest management and disturbance impact on bat habitat use and populations
  3. effects of white-nose syndrome, and
  4. bat monitoring protocols.

Her research interests also include ecology, evolution, and conservation of mammalian species in natural systems and how these species adapt to anthropogenic changes.

Because prescribed burning is a common forest management practice across the southern and eastern U.S., understanding how foraging bats respond to forest structure changes generated by fire is vitally important.

Loeb and colleagues monitored bats in 164 burned and unburned forest sites for in 2014 and 2015 to compare their foraging and commuting habitat use in the different environments.

A key finding of this research was the positive impact of prescribed fire on bat habitat usage. All bat populations in the study were more likely to use burned areas relative to controlled, unburned sites. Overall, bats were detected by Loeb and colleagues at 94 percent of burned sites compared to 83 percent of un-burned sites.

“For a number of species and other taxa, prescribed fire really is a benefit,” explains Loeb. Fire removes the understory, which results in a thinned forest area with more room for foraging. Many forests in the eastern and southern U.S. are second growth forests and can be too dense for bat populations.

Not all bat species respond in the same way to similar management practices. Some treatments, like clearcutting, may be beneficial for larger bat species but not for smaller bats. “One treatment does not fit all sizes!” explains Loeb.

tricolored-bat
Tricolored bats are among a dozen native North American species with confirmed cases of white-nose syndrome. Photo by David J. Thomas, courtesy of Flickr.

More specifically, occupancy by the Myotis and tricolored bat species (Perimyotis subflavus) was found to be lower in sites that received moderate severity burns compared to sites that received low severity burns. These results indicate that retaining some unburned forest sites paired with a mosaic of high and low severity burn sites will result in the most favorable foraging conditions for the wide range of forest-residing bat species in the southern and eastern U.S.

In order to meet the diversity of bat habitat needs on a landscape scale, an area needs “sufficient young, regrowth and mature forests,” says Loeb. In order to ensure a variety of different forest types across the U.S., land managers are thinking at broad scales and over long time periods.

However, most research on bat population dynamics is conducted during the summer months. This has created a hole in researchers’ understanding about the effects of different forest management practices on bat habitat use and populations during the fall, winter, and spring seasons.

Loeb looks forward to resuming a research project that was cut short due to the COVID-19 pandemic. She and colleagues hope to restart a study of the response of bats to burn, clear-cut, and control sites in all four seasons of the year.

While one management practice cannot be the ideal solution for all species, incorporating Loeb’s research findings into bat management practices moves us one step closer to maintaining safe habitats for of bats of all sizes – large and small.

Read the article about the effects of fire on bat habitat

Read the article about bat responses to silvicultural treatments.

For more information, email Susan Loeb at susan.loeb@usda.gov.

Access the latest publications by SRS scientists.

 

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