Environment: Bat Patrol

It’s a bird! It’s a plane! No, it’s ... the Hawaiian hoary bat?

UP TO BAT: The hoary bat eats moths, beetles and flying termites. photo: courtesy Honolulu Zoo.

The Hawaiian hoary bat, or ‘ope‘ape‘a, is somewhat of a mystery in the Islands. Not only are the bats tiny—put three quarters in your hand and you’ll get an idea of their weight—they are also nocturnal and prefer the James Dean type of loner lifestyle, making it nearly impossible for scientists to determine their population size.

Yet the species, which, incidentally, is Hawai‘i’s only native land mammal, isn’t completely inaccessible to researchers. A three-year project by the U.S. Geological Survey (USGS), wraps up this June and is the first large-scale study ever conducted on the bats—which were listed as endangered more than 35 years ago. Its results will help to develop a new monitoring program designed to manage the bats’ safety and increase its numbers.

To gain an understanding of the bat’s movements and its preferred habitat locations, nylon nets were used to capture individuals in the Hilo and Hamakua Coast regions of the Big Island. Each netted bat went through a sort of booking process—its weight and size documented, hair clippings collected, photo taken. Then researchers placed a small radio-tracking device between the bat’s shoulders with a medical adhesive. Weighing less than half an ounce, the gadget is outfitted with a guitar string, which serves as an antenna signaling the bat’s location to scientists, before it falls off after two weeks.

“We’ve tagged about 30 bats over the three-year period,” says Frank Bonaccorso, wildlife biologist for USGS. “Within one night we’ve had individual bats move a pretty good distance, within five to 12 miles in one direction before returning to where they started.”

Researchers have also discovered that moths are the bats’ delicacy of choice.

A new collaborative effort, bringing together the Research Corp. of the University of Hawai‘i (RCUH), the National Park Service, U.S. Fish and Wildlife Service and USGS, will place devices, aptly called bat detectors, in the field for a weeklong period to record the vocalizations of the bat onto a memory chip. “This will tell us if bats are flying over the area and at what time of night, so we can look at how important specific sights and habitats are,” says Bonaccorso. “If we put the detectors in the same place for a couple of years, we’ll be able to tell if the population is stable, or if it’s increasing or decreasing.”

Biologists from RCUH also used the bat detectors in 2005 to determine the bats’ presence in six of Hawai‘i’s national parks, including Hawai‘i Volcanoes on the Big Island and Kalaupapa on Moloka‘i. Of the six, the Big Island’s Pu‘ukohola Heiau was the only location where the bats weren’t found. These inventories will be used to establish a long-term monitoring strategy, starting in 2008, to protect the species inside of Hawai‘i’s national parks.

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