Winter in the South can bring about a sharp change in conditions that impact forests and their many inhabitants. However, new research from the University of Georgia Warnell School of Forestry and Natural Resources finds that, despite these seasonal shifts, forest management efforts are supporting healthy bat populations.
As white nose syndrome, a deadly fungal disease, ravages bat populations, wildlife ecology and management professor Steven Castleberry wanted to ensure all other aspects of bat livelihood were being maintained.
"There's nothing really we can do about that disease. All we can do is continue to provide proper habitats," Castleberry said. "As those populations recover, we ensure that those quality forests and habitats are still there."
Previous research looked at how bats survived in managed forests during the summer, but the role winter has on forest conditions and prey availability remained unexplored.
Foundational forestry
Castleberry and Santiago Perea, a UGA Ph.D. student at the time of this study, examined bat activity over 400 nights by using the creatures' echolocation.
As bats moved through Southeastern forests, the team found they relied on large areas of semi-open, canopied forest stands, otherwise known as varied stand structure according to Castleberry. The balance had to be just right - an open canopy allowed bats to fly and feed efficiently but dense, closed-canopy areas with thick vegetation made flying difficult.
"These types of forests are pretty good for bats because they're like a mosaic. Bats don't need just one type of forest, they need a lot of different types of forests, and that's what they provide out there with these stands in various stages of succession and ages," said Castleberry.
Castleberry points out that most privately owned forests already provide a suitable balance for bats during the winter. Moving forward, forest managers should maintain this equilibrium rather than make drastic changes.
"It's good for business, but it's also good for the environment, and it is going pretty well for the bats, too," he said.
UGA researchers study tricolored bat (Perimyotis subflavus) species to understand winter diet changes in working southeastern U.S. forest.(Submitted photo)
Pinning down prey
Colder weather also had a direct impact on meal availability for bats. When temperatures dipped, nocturnal flying insects - an integral part of bat diets - were less active and easier to catch. That's great news for bats.
"All of our bats in the Southeast are insectivores, so they're dependent upon insects," he said. "Nobody had really studied insects in the winter as much as they had in the summer, so we were especially interested in insect abundance."
With the assistance of Kamal Gandhi, co-author and interim associate dean for research, Castleberry's team was also able to identify a variety of insects in these forests.
So while cooler temperatures did affect insect activity, Castleberry found another perk of a diverse forest - the more mixed the stand structure, the greater the variety of bugs flying around.
No need to over-strategize
The researchers emphasize that a varied forest structure is crucial for bat survival. Properly balancing every stage of forest management helps maintain the right mix of vegetation for our flying friends.
And it's all connected. Bats make up 20% of all mammal species, so their roles in things like insect population management and seed dispersal can't be overstated. One estimate puts the value of bats at more than $22 billion for the effect they have in agricultural systems by controlling insect pests.
"Nature, and working forest ecosystems, in this case, are often more complex than we assume, and our findings highlight the intricate interactions they provide," said Perea, a co-author on the study. "This underscores the need for diverse forest management strategies to support a healthy bat community."
This study was funded by the National Council for Air and Stream Improvement, and was also contributed to by co-authors Amanda Vicente-Santos, Angela L. Larsen-Gray, Daniel U. Greene and Brittany F. Barnes.
