Monitoring bat populations

A bat opens its mouth in the gloved hand of a wildlife biologist. Colorado Parks and Wildlife biologists April Estep and Cassidy English are on the frontline of scientific efforts nationwide to monitor bat populations for “white-nose syndrome.”


COLORADO SPRINGS – In a muddy creek drainage on a chilly Sunday evening in May, Colorado Parks and Wildlife terrestrial biologist April Estep looked for a rock large enough to brace a piece of steel rebar she had hammered into the soggy ground.

Estep and CPW’s Cassidy English, a district wildlife manager, were erecting mist nets across a pool created by a sliver of water from the unnamed creek. Two nets measuring 24 feet wide and 10 feet high were already stretched across the drainage.

They were anxious to finish because the sun was slipping below Pikes Peak to the west. Soon, any bats roosting in surrounding trees, rock outcroppings or mine shafts would emerge and look for a drink before heading out to hunt insects for the night.

Once the nets were up, Estep and English climbed out of the mud and moved to a small table that would serve as their creekside laboratory for the night. On it was an assortment of scientific tools they would use if they were lucky enough to catch any bats.

Estep and English were on the front line of scientific efforts nationwide to monitor bat populations for “white-nose syndrome” – a deadly, tissue-eating fungus that grows as a fuzzy white substance on bats’ noses, wings and other hairless areas.

The syndrome is believed to have invaded the U.S. around 2006 from Europe, where bats are immune to it. It has been wiping out colonies of bats by the millions along the East Coast and in the South ever since.

Biologists are desperate to find a way to stop it because bats are so important to the ecosystem. They are important pollinators, consume insects and may slow the spread of diseases like West Nile virus.

Colorado is h​ome to 18 species of bats, including some that migrate through in summer. CPW biologists have spent eight years keeping vigil for evidence of white-nose syndrome as it slowly approaches Colorado.

On this night, several teams of biologists like Estep and English fanned out across a remote, wooded area south of Colorado Springs. The teams erected nets, infrared cameras and acoustic bat detectors, then waited for web-winged mammals to emerge in the dark.

For Estep and English, it was hours before a silver-haired bat flew into their net. It was the only bat they would see that night. They were lucky – some of the other teams caught no bats.

Plenty of bats were flying around. But gusting winds, Estep speculated, were causing the nets to move so much the bats could detect them with their echolocation, or biosonar system in which they emit a sound and listen for it to echo back off things in their environment.

Finally, around 10:30 p.m., one of the mist nets rustled. Estep and English scanned the net with their headlamps and saw a small, dark figure. They ran toward it, discovered it was a bat and quickly went to work with double-gloved hands to free the bat.

The bat squealed fiercely and bit the biologists’ gloved fingers as they worked to free it from the net. In a few moments they deposited it in a small cloth bag. Then they hurried back to their creekside lab and went to work under the light of their headlamps and the full moon, when it emerged from swiftly passing clouds.

Estep weighed the bat as English recorded the data. They measured its wings, held it on its back and examined its underbelly. Finally they stretched its wings over an ultraviolet light to check for signs of the fungus. They took photos to document it top to bottom.

The bat was uninjured by being caught and examined, but it was clearly unhappy, given its squeals and repeated plunging of its tiny fangs into the biologists’ gloves. After a few minutes, it calmed down and Estep laid it on the table to rest.

Once Estep and English had gathered all the data and completed the exam, they held the bat aloft, hoping it would fly away. It opted to rest instead. Since it was a tree-roosting bat, Estep placed it on the trunk of a nearby tree, and it quickly scrambled up to a perch. A few moments later it took flight.

The team kept vigil until midnight, even as the temperature dropped – a spring storm dropped heavy, wet snow the next day – and no other bats appeared. But the CPW biologists took the results in stride.

“This is pretty typical of our bat surveys,” Estep said. “There are never any guarantees we’ll catch bats.”

But the work is too important to quit, even when it means not getting home until 3 a.m. after a night of mud, cold wind and rain and catching just one bat.

“I feel a sense of urgency to contribute to the research and stay on top of what’s happening to our bats,” Estep said. “This work is going on nationwide and we need to do our part to protect our bat colonies.”

She and other CPW biologists will spend the summer conducting similar all-nighters in search of bats. They will drive thousands of miles crisscrossing Colorado to erect acoustic bat detectors, collect data and track bats’ movements.

They will keep vigil at places like the Orient Mine in the San Luis Valley, where a massive colony of 250,000 bats spends the summer. They will patrol places like Devil’s Head mountain west of Castle Rock where bats gather in its rocky outcroppings and crevices.

They will wade into mud and muck and spend long nights catching bats, sampling tissue and guano and shining lights on wings.

“We put in the long hours in challenging conditions because we need to learn all we can as quickly as possible,” Tina Jackson, CPW species conservation coordinator, said. “There is still so much we need to know about these unique animals. But due to the threats they are facing, we are working against the clock.

“White-nose syndrome is knocking on our door, so now is the time to figure out all we can about these secretive species.”

Jackson said CPW biologists are not discouraged when a night of research results in just a few bats being caught and studied. She said each bat provides critical data and adds to the body of knowledge.

“Netting efforts like this one, plus acoustic monitoring through the North American Bat Monitoring program as well as roost monitoring, all provide important baseline information about our native bat species,” Jackson said.

“We don’t have the luxury of waiting for good weather or doing research when it’s convenient. We have to get out in the field now, before our bat populations experience too many changes from threats like white-nose syndrome, wind energy development and climate change.”

If you have bat encounters, you can phone in a report to CPW at 303-297-1192 in Denver or 719-227-5200 in Colorado Springs.

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