Game and Fish Expands Efforts to Understand White-Nose Syndrome
According to the Wyoming Game and Fish Department (WGFD), bat biologist Laura Beard and non-game technician Frank Stetler recently completed a bat hibernation survey in the Bighorn Mountains. In addition to recording the species and number of bats seen, samples were collected to look for evidence of white-nose syndrome.
In previous surveys, the cave has hosted as few as 10 hibernating bats in 1995 and as many as 33 in 2003. This year’s count was 31 individuals representing four species including: big brown bat, little brown myotis, western small-footed myotis, and the Townsend’s big-eared bat.
This survey is a part of an ongoing effort to better understand the fungus that causes white-nose syndrome (WNS). The fungus grows on bats’ skin, appearing on the face and wings as white fuzz. While the growth of the fungus may not kill the bat outright, the irritation it causes often forces bats to wake during hibernation.
“They do normally arouse sometimes during hibernation, but white-nose syndrome causes a physiological cascade that makes them arouse more frequently,” said Beard, in a press release. “This frequent arousal expends energy and without a supply of insects available in the winter, bats can starve or die from exposure when exiting the cave during winter conditions to search for food.”
The disease was originally discovered in New York in 2006 and has killed millions of bats in the east and Midwest and continues to expand westward. To date, the disease has been found in 32 states and seven Canadian provinces. In June 2018, a little brown bat near Fort Laramie State Historic Site tested positive for Pseudogymnoascus destructans (Pd), the fungus which causes the disease, though it did not show outward signs.
Subsequently, the Wyoming Game and Fish Department was awarded $29,437 to broaden white-nose monitoring and tracking of the little brown myotis bat to evaluate how they use their surroundings in the winter. Although most of the bats caught during statewide bat surveys are from the Myotis genus, relatively few of these are found during winter cave surveys.
“We have only found seven little brown myotis hibernacula [hibernation sites],” WGFD nongame bird and mammal supervisor Zack Walker said, in a press release. “This suggests the majority of little brown myotis go undetected and are never swabbed with the standard winter survey method.”
Biologists with the Game and Fish Department have conducted hibernation surveys of bats for 25 years, but in recent years, have added testing for Pd to document if and when the disease arrives in our area.
“We have done hibernation surveys for a long time and we are monitoring the population that way,” said Beard. “While we don’t have a complete understanding of where our bats hibernate, these caves can be an indication of population trends. We are also looking for signs of the disease, such as any white fungal growth on the bats or any signs of mortalities inside or outside of the cave.”
Beard surveys several hibernacula each winter and tests two or three of these for Pd each year. Caves are on a rotational schedule, being surveyed no more than once every two to three years to minimize disturbance of hibernating bats. On Jan. 15, an unnamed cave in the Bighorn Mountains was on this year’s schedule, so Beard and Stetler traveled there to conduct tests.
After a two-and-a-half-mile hike through private property, they arrived at the cave. Wearing protective coveralls and carrying multiple sources of lighting, the pair climbed through the entrance and began the survey. Walking slowly and scanning the ceiling, walls, and crevices for bats, they recorded the number and species seen in the cave’s 1,000-foot length.
Additionally, Beard collected 30 samples to be tested for Pd from the cave. Most samples consisted of soil substrate and bits of bat guano collected in small plastic tubes, but in a few cases, bats were hibernating low enough on walls to allow a swab to be gently rubbed on the exposed membrane of their forearms and muzzle. All of the samples were sent to the USGS National Wildlife Health Center to be tested.
Upon exiting the cave, they followed a strict protocol for decontamination of all gear and items that entered the cave. Shoes, headlamps, coveralls, pencils, paper, and other items were placed in a large plastic garbage bag that was carefully sealed and carried on the return hike. All the fabric items were submerged, or ‘hot dipped,’ in 140-degree Fahrenheit water for 20 minutes, before being used in another cave, to prevent potential contamination between caves. Items that could not be submerged were wiped down with Lysol wipes containing ammonia, which has been found to kill the fungal spores in laboratory testing. This decontamination procedure is outlined by the White Nose Syndrome Response Team and is recommended, or in some areas, required, for anyone who frequents caves.