A few miles outside of Stilwell, Oklahoma, Matt Fullerton, endangered species biologist for the Oklahoma Department of Wildlife Conservation, waits near a cave entrance on the Ozark Plateau National Wildlife Refuge. As the sun settles low on the horizon, bats begin to launch from their daytime roosts to feed on an abundance of night-flying insects.
“This is an incredibly important spot for bats,” Fullerton said. “In fact, the U.S. Fish and Wildlife Service manages this area specifically for bats – protecting the caves for winter hibernation and spring maternity sites, and the surrounding forest for foraging habitat.”
The wooded Refuge and the network of limestone caves located just below the surface are home to at least ten species of bats, all nocturnal insect-eaters. Three of these species are federally protected.
The Ozark big-eared bat, one of the rarest mammals in the state, can be found in Oklahoma's longest known cave system located on the Ozark Plateau National Wildlife Refuge. (Jena Donnell/ODWC)
For the past three years, this bat hotspot has been the meeting place for biologists interested in counting the number of bats using the area and monitoring the population for the effects of a relatively new bat disease known as white-nose syndrome. U.S. Fish and Wildlife Service biologist Richard Stark and Environmental Solutions and Innovations’ Kory Armstrong and Lynn Robbins have been the primary organizers of these efforts.
“Trained biologists have been going into the caves in late winter to count hibernating bats for years. With advancements in technology and bat detection equipment, they’ve been able to add summer echolocation surveys, or listening surveys, to the mix. More recently, they’ve been trapping bats in the spring and fall as the bats come out of the caves. That’s what we’re doing here tonight,” Fullerton said.
Bats are found on the Refuge year-round, but begin to congregate at caves in the fall before they go into winter hibernation. During this “fall swarming,” bats are feeding and gaining weight for the upcoming winter, and mating. The pups are born after the females wake up in the spring.
This fall bat assembly is a great time for biologists to check in on the population.
Biologists have been catching and examining bats at the Ozark Plateau National Wildlife Refuge for the last three years to better understand the size and health of the populations. (Jena Donnell/ODWC)
“When bats are caught at the mouth of the cave or in a special mesh net set up near the cave entrance, they are taken to a central processing area where they are identified,” Fullerton said. “The weight and forearm length of each individual bat are also recorded. These measurements help confirm the identification.”
Small, unique, identification bands are put on the wings of threatened or endangered bats after they are processed.
“If the banded bats are captured again in later surveys, it helps us better understand how many bats are in the area. If a lot of banded bats are recaptured, it indicates the population is relatively small. If only a few banded bats are recaptured, it means the population is relatively large,” Fullerton said.
One of the bats banded as part of the survey, the northern long-eared bat, was recently classified as federally threatened.
This northern long-eared bat, a federally threatened species, was recaptured during the fall 2017 trapping efforts. (Jena Donnell/ODWC)
“These bats are incredibly difficult to count in the winter,” Fullerton said. “They are only a few inches in length and like to hibernate in small crevices. The banding portion of this study has revealed many more northern long-eared bats are using the cave than originally known.”
Before bats are released back into the night, biologists check for signs of white-nose syndrome. The wings are carefully examined and scored on a scale of 0 – no damage, to 3 – severe damage.
“White-nose syndrome is disease caused by a fungus. It affects hibernating bats; the growing fungus wakes the bats up when insects are in short supply. Because their food source is limited, the diseased bats may eventually starve,” Fullerton said.
While the fungus associated with the disease has been documented in this federally protected cave, clinical signs of the disease have yet to surface in the county. Delaware County, one county to the north of Refuge, tested positive for the disease last year.
“The Wildlife Department will partner with the U.S. Fish and Wildlife Service next year to help these surveys continue,” Fullerton said. “We’ll be adding another step to the process next spring. Bats will still be banded, but we’ll also add a small tracking device to the rarest of bats to find out how far these bats are flying.”
“This technology will allow us to track the bats as they move about and forage on the landscape. Ultimately, we hope this next step helps us better manage Oklahoma’s bats.”