Insight into the Lives of Hoary Bats Thanks to GPS Tracking
6 Dec 2016
The migratory hoary bat (Lasiurus cinereus) can be found roosting in the redwood forests of California. Capable of flying for hundreds of miles, the bats are thought to make their way through western North America, finally reaching the north coast of California to hibernate. This is an unusual trait as most bat species either migrate, or hibernate – they generally don’t do both.
One of the largest species of bat found in North America, the hoary bat is around five inches long, and takes its name from its unusual frosted fur.
Using GPS tracking, U.S. Forest Service Pacific Southwest Research Station researchers have recently documented the first recorded evidence of its kind that shows that these bats go into a state of hibernation. The study, that was published early October, 2016, reports various newly recognized hoary bat behaviors.
Forest Service ecologist, and lead author of the report, Ted Weller, stated,
“It’s commonly assumed that species that migrate do so to reach areas that allow them to continue feeding and remain somewhat active throughout the winter, but our findings surprised even our own research team by showing that hoary bats spend much of the winter in hibernation.”
The study began within Humboldt Redwoods State Park back in September 2014, with Weller and his team fitting a GPS tracking device to several of the bats, whereas others were tagged with a device that monitored body temperature, light levels, and activity, allowing them to find out how bats react to changes in weather conditions.
After a month, a pair of the GPS-fitted bats were caught, and the data from the devices downloaded. One bat behaved as the researchers expected, and only travelled four miles from the site of initial capture. However, the second bat was different. It flew from 30 to 40 miles each day.
A third bat, showed the most interesting behavior when it was caught a few months later. It had flown more than 600 miles through southern Oregon, interior California, over to the Nevada-California border, then back into interior California again.
The monitoring devices on the second bat group gave further new insight into the species. One of the two animals recaptured in spring showed, that based on its inactivity, and lowered body temperature, it had been hibernating from November 2014 through April 2015.
It’s thought that these newly discovered behaviors are as a result of the bats, that roost in trees rather than in caves, evolving to hibernate in the Redwoods due to the shelter, moisture, and cool temperatures of the area.
The bats would freeze if they hibernated in their usual summer territories.
Weller said of the bats,
“Knowing more about their lives outside of the summer months will help us better understand what steps might best promote their conservation.”
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