Data Loggers Shed Light on Mysterious Bat Disease

Looking to combat a serious disease threat to bat populations in the northeastern US, researchers used data loggers to measure ultrasonic sounds and validate bat echo-location during the winter.

Wildlife researchers are alarmed at a serious threat facing bat populations in the northeastern United States. It’s estimated that one million bats have died in hibernation and researchers are scrambling to understand why. The unexplained illness is known as “white-nose syndrome” (WNS) because many affected bats develop halos of white fungus on their faces.

Carl Bakker is a researcher studying this mysterious, fast-spreading disease affecting bats in the Northeast.  Below he discusses an early warning system he developed to determine how far west the syndrome will migrate.

WNS in bats is becoming a very serious problem and is causing tens of thousands of bats to die each year. What happens with the syndrome is that when bats go into hibernation for winter, they shut down their metabolism and immune system so they can conserve energy. When they get the syndrome, their immune systems kick back in, which in turn burns fat. The bats then go looking for food in the middle of winter when there is none. Eventually, they starve to death. Last fall, with the WNS coming, we were trying to come up with an early warning detection system that was cost-effective.

We were operating on the philosophy that unless we know how many bats we have, we don’t know how many we’re going to lose. With WNS, there is a 90% to 95% mortality rate.

To create this early warning system, we needed to gather microclimate data in bat caves and try to determine the flight path of the bat so we could get a sense of where the bats will come up from.

In talking with bat detector designer Tony Messina in Las Vegas, we came up with the idea of building a prototype ultrasonic sensor/data logger capable of measuring ultrasonic sounds in 40 kHz range. To record the data, we needed a low-cost, portable data logger that didn’t emit ultrasonic sounds in bat hearing ranges. The Onset data logger – a HOBO U12-006 – met these criteria so it was designed into the prototype.

Initially, we were going to place the sensor and logger, which are mounted on a tripod, in Mystery Cave located in central Montana in the Pryor Mountain Range.

Since it had snowed so early this past year, we could not get to the 8,000-foot level on the mountain where the cave was. So instead we used the Dandy Mine, an abandoned uranium mine where we knew bats were hibernating. The outside temperature on the mountainside was -12°F, but inside temperatures were around 38°F.

We set the system up in the mine, with the idea that it would run all winter to see if our idea was working. The detector constantly scans for ultrasound in the 40 kHz range. When a sound is detected, it stores a value to a chip. Every 15 minutes the data logger "wakes up" and sends a signal to the sensor. The sensor then downloads a value based on the number of calls to the data logger and resets its storage to 0. The cycle repeats every 15 minutes.

In early spring, we pulled it out and discovered that it did work: we were able to detect ultrasonic activity in the mine. Using HOBOware software, we analyzed data and it showed that this project has potential in terms of validating that the bats are echolocating during the winter. In late spring, when we can get up to the 8,000-foot level in the mountains, we’re going to be placing the system down into a shaft in Mystery Cave, 500 feet back from entrance. We are also going to deploy temperature/relative humidity data loggers at two ends of a breakdown area at the end of the pipeline back 900 feet inside the mountain.