By Peter Sachs / The Bulletin
Published: July 27. 2008 4:00AM PSTJess Jordan and Shawn Zumwalt spent Thursday night scanning the skies and scouring caves southeast of Bend for a glimpse of a threatened species of bat. No luck — but the survey will continue through the summer. If Townsend’s big-eared bats make their home in caves across the Stevens Road Tract, that could affect development near there.
Jess Jordan and Shawn Zumwalt counted more than 20 bat calls from caves like this one during a survey on the state-owned Stevens Road Tract southeast of Bend on Thursday night. (A flashlight illuminated the entrances to this cave in this long exposure.)
Jess Jordan, a biologist with the Department of State Lands, uses his headlamp to peer into cracks and crevices in a cave wall, looking for evidence of bat activity. “The farther you go in (to the caves), the more stable the temperature is, and that’s what they need.”
Jess Jordan and Shawn Zumwalt spent Thursday night scanning the skies and scouring caves southeast of Bend for a glimpse of a threatened species of bat. No luck — but the survey will continue through the summer. If Townsend’s big-eared bats make their home in caves across the Stevens Road Tract, that could affect development near there.
For an audio slideshow of Jordan and Zumwalt’s trek through the caves across the Stevens Road Tract, Click Here.
The Batbox registered the sound of soft static as Jess Jordan knelt 20 feet from the small entrance to a lava tube cave, waiting for bats to come out and start feeding.
The sun had just set across the Stevens Road Tract just southeast of Bend’s city limits. Jordan and Shawn Zumwalt were starting a night of bat surveys.
The goal: determine whether the threatened Townsend’s big-eared bat is using any of the caves dotting the tract for summer roosts.
Three ticks in quick succession came out of the Batbox — which translates the sound of a bat’s high-frequency sonar into tones the human ear can hear.
Jordan stared intently at the cave entrance, willing the bat to come out, while Zumwalt noted the reading on a tally sheet on a metal clipboard.
It was about 78 degrees out with a slight breeze. A small swarm of insects dipped and rose with the breeze just outside the cave, perfect food for a hungry bat.
The Department of State Lands, which owns the 640-acre chunk of land, wants to eventually see it developed with hundreds of homes. The caves, part of a regional complex know as the Horse Lava Tube System, would remain as part of unmodified open space. But having people and homes near the caves could disturb the sensitive bat species.
Townsend’s big-eared bats are notable for ears that can be more than an inch long. They range across the Western United States, favoring abandoned buildings, mines and caves, but their numbers are dropping because they have so little tolerance for human activity.
Jordan is a regulatory biologist in the department’s wetlands and waterways division with a background in bats. Zumwalt is a land manager whose territory covers much of Eastern Oregon.
The bat survey, which lasted five hours Thursday night, is one of several Jordan and Zumwalt will conduct this summer to gather data on which species of bats are using the area.
Their primary tool is the Batbox, a hand-held ultrasonic microphone the size of a large box of matches. It records high-frequency sounds in the range of 26,000 hertz onto a digital recorder. A small speaker on the device translates the sounds into ticks, hums and buzzes that Jordan and Zumwalt can use to determine if a bat is passing through or feeding. Only by analyzing the specific sound pattern in computer software later will they be able to determine the exact species of bat in each recording they gather.
A half-hour after he heard the three ticks at the first cave, Jordan hadn’t picked up any other signs of a bat. He stood up and turned a slow circle, the Batbox outstretched toward the sky, and checked for other bats in the area. A few minutes later, a single bat flew overhead.
The Batbox emitted an irregular sound, like a child beating a toy drum. Jordan suspected it was a big brown bat traveling through the area in search of food.
A rare habitat
A normal week’s work for Jordan usually focuses on wetlands anywhere from Hood River County to the Wallowa Mountains. He deals with everything from bullfrog infestations to county road departments that decide to dump hundreds of cubic yards of rocks down riverbanks to property owners who attempt to fill in protected wetlands.
As an undergraduate at Oregon State University, Jordan got hooked on bats, taking a one-credit introductory course from a professor who would stay up several days in a row, recording bat sounds at night and exploring caves the next day to look for signs of bats.
Jordan surveyed bats in the Willamette Valley for his thesis, once recording more than 2,000 calls over eight nights of observation.
So when the department realized it needed more details on the bats living on the Stevens Road Tract, it made sense to put Jordan on the mission.
“What we’re trying to do is just get a good understanding of the bat usage of the lava tubes, and then the species of the kinds of bats that are using it,” said John Lilly, a manager in the Department of State Lands’ Salem office.
Jordan has gotten help from the Oregon High Desert Grotto, a local group of cavers who have measured and mapped each of the Stevens Road Tract caves.
“When we survey, we also kind of catalog everything we see,” said Matt Skeels, the chairman of the group. “Those caves don’t have much because they do see a lot of impact just from the casual person poking their head in.”
Some of the caves have been tagged with graffiti, their openings littered with trash and shattered bottles. But others are harder to find and have small entrances tucked away.
There’s anecdotal evidence of Townsend’s bats living in the area, but not enough information to figure out if the bats stay year-round or if there’s even an established colony like the one in the Skeleton Caves farther south.
“It’s likely if they’re in the area they would be using those caves, and that’s a pretty rare habitat,” said Nancy Allen, the head adviser in Oregon State University’s Department of Fisheries and Wildlife.
The caves on the Stevens Road Tract that people haven’t vandalized make for better habitats. Skeels and Jordan agree people shouldn’t be checking them out just for the sake of trying to see a bat.
“It is kind of a unique environment, which serves as a nice place, particularly for the Townsend’s bats, that are really finicky,” Skeels said. “It’s easy to push them out.”
Unmistakable sounds
Night settled in fast as 10 p.m. came and went. Only the faintest glow of the day remained on the western horizon, and the smoky ribbon of the Milky Way started to become visible overhead.
The Stevens Road Tract may feel remote, yet the sound of cars passing on Southeast 27th Street is hard to miss. The glow of Bend’s lights creates a pale silhouette of Pilot Butte in the distance, and the red lights atop antennas on Awbrey Butte remind you that you’re not quite immersed in nature.
Howls of coyotes floated from far away to the north, then a few minutes later, yips came closer as the coyotes seemed to be communing with the wail of emergency sirens somewhere in the city.
Jordan and Zumwalt instantly dropped their conversation as they turned toward the entrance to the second cave of the night.
From the sounds, Jordan determined a bat had just made three passes through the area.
After Zumwalt noted the passes on his tally sheet, Jordan kept the Batbox trained in the cave entrance.
Then, to Jordan, came the unmistakable sounds of a bat circling inside the cave before exiting. It sounded something like a spring stretched inside a cardboard tube being hit with small pebbles several times each second as the bat sent out sonar echoes. In the span of a second, the echoes quickened and turned into a short buzzing sound — the bat closing in on an insect, the sound waves compressing into a nearly continuous tone.
After the 45 minutes of recording were up, Jordan and Zumwalt headed into the cave to check for any signs of the bat they heard.
Scrambling in feet first over the sand and large rocks at the entrance, the temperature soon dropped a few degrees. The faint but pungent scent of feces — probably guano — hung in the air. The cave is less than 4 feet high at first.
There are no stalactites or stalagmites, though tiny white droplets of hardened calcite cling to the ceiling in patches.
Zumwalt and Jordan trained their bright white headlamps into each crevice they passed, looking for any sign of a bat’s roost or guano droppings.
The basalt forming the cave’s walls and ceilings is split with innumerable cracks several feet long and 6 inches deep or more — ideal places for a bat to tuck itself away deep inside.
“There’s a lot of great-looking crevices where he could just sneak in,” Zumwalt says.
As the cave opened up into a main chamber with an 8-foot ceiling, the temperature had dropped to the low 50s. Behind a big boulder of basalt, the cave again narrowed to a crawl space. Zumwalt speculated that the cave connects with another in the Stevens Road Tract.
“The farther you go in, the more stable the temperature is, and that’s what they need for the winter roost,” Jordan says.
More work ahead
It will take a more detailed survey inside the cave to determine exactly how many bats are living in the cave and how long they’ve been roosting there.
There’s still plenty of time for that work, since the Stevens Road Tract isn’t yet slated to be part of Bend’s urban growth boundary.
Jordan is hoping to recruit Oregon High Desert Grotto to check the caves more thoroughly for evidence of bats living or hibernating in them.
In a more perfect world with greater funding, Jordan would be able to set up remote ultrasonic microphones in front of each cave on the property and let them record simultaneously to get a more complete record of bat activity.
Jordan and Zumwalt won’t know until they review the recordings of the 20-odd bat calls they heard Thursday night whether any of them were from the Townsend’s big-eared bat.
Monitoring another cave shortly before moonrise at 11 p.m., the loud clicking of a passing bat made Jordan look up just in time to see it fly less than a foot from his head before traveling into the night.
“That’s not erratic flight,” he said later. “It’s all planned.”
Peter Sachs can be reached at 541-617-7837 or psachs@bendbulletin.com.
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