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October 30, 2023

From the latest wildlife tracking tech to collaboration with recreationalists, USGS scientists and partners are using innovative methods to study bats in national parks and get ahead of the threats facing bats today.

A researcher holds a small bat with transmitter in a gloved hand
A California myotis with a transmitter, part of a study of bats in Yosemite National Park.

A rock climber high on the iconic granite walls of Yosemite Valley. River rafters floating the Colorado River as it runs through the Grand Canyon. A solar powered radio antenna array attached to the spillway of a former dam in Olympic National Park. What do these things have in common? They are all parts of exciting new ways USGS and National Park Service scientists have been studying bats in national parks.

One of those scientists, USGS wildlife biologist Rebecca McCaffery, summarized some of the advantages of working in the parks, “National parks are inspirational places to work, and can allow us to distill what's happening with wildlife populations in the absence of other major stressors.”

Read on to learn how McCaffery and other USGS scientists are learning about the bats that live in some of our western national parks.


Olympic National Park: Big Network, Tiny Tags

The northwest corner of Washington state is home to three large mountainous national parks: Olympic, Mount Rainier, and North Cascades National Parks. They are known for their lush green forests, snow-capped mountains, teal blue lakes, and rocky coastlines. They are also home to ten bat species, a poorly understood group of species integral to these western ecosystems.

Bat biologists at the USGS and National Park Service have their eyes on the Washington parks because it is an important location for the study of white-nose syndrome, a fungal disease that has killed millions of bats across the country. White-nose syndrome was first documented in New York in 2006, and most of its impacts so far have been in the eastern to central United States, with several bat species now listed as threatened or endangered due to the disease. In 2016, though, white-nose syndrome was detected in Washington, the first western state to document it, and the disease and the pathogen that causes it have since been spreading throughout the state and other western states.

A masked and gloved researcher holds up a bat wing to the light while another looks on
Researchers examine a bat wing while in the process of capturing bats to attach tiny Motus radio tags to track their movements.

Though white-nose syndrome has been well-studied in other parts of the country, scientists and managers are uncertain how the spread of the disease will play out in the West. The bat species in this region have different winter activity patterns and hibernation behaviors use than other well-studied and declining populations in other parts of the continent. Bats are most vulnerable to the disease during colder months when hibernating, but bat activity during these times is not yet well understood.

Until recently, it’s been hard to track individual bats over long distances or time periods. Bats are too small to carry the GPS tags that have allowed scientists to uncover the long-distance movements of mammals and large birds. A new type of animal tracking technology is now making it easier to study small flying animals like bats. It’s called the Motus Wildlife Tracking System, run by an international collaborative research network. The Motus network is made up of arrays of more than a thousand automated radio telemetry receiving stations around the world that detect signals from tiny tags worn by animals. The nanotags, as they are called, are so tiny that they can weigh as little as a single raindrop and can last from 20 days to as long as the life of the animal, depending on the model.

The receiving stations are deployed and maintained by collaborators around the world—including, as of this year, bat biologists from USGS and National Park Service. In September, USGS scientists and NPS partners installed a Motus array in Olympic National Park, on the side of a spillway on the former Glines Canyon Dam and began to capture bats and fit them with nanotags.

A platform with antennae overlooking a river with a mountain in the background
A Motus tower installed on the spillway of the former Glines Canyon Dam in Olympic National Park. The solar-powered array of radio antennae will detect the signals send by tiny transmitters known as “nanotags” that have been attached to small flying animals. This tower was installed to study bat movement behavior.

“We tapped into a fabulous network of bat biologists and volunteers both to tag the bats and design the work, but also to build the tower! We have really felt the power of collaboration working with the parks, a local tribe, and other USGS research centers to achieve our goals,” said McCaffery.

In combination with existing acoustic monitoring data, scientists will gain a better understanding of how white-nose syndrome may affect bats in the western states.

A group of scientists sit on the ground, working by headlamp light to get ready to measure a bat
A team of biologists prepares to measure, weigh, and tag a captured bat.

“We really don't know what bats are doing in the fall and winter in this region,” said McCaffery. “Using Motus in the way we are will allow us to take a peek behind the curtain and start to understand this critical part of their ecology in relation to disease vulnerability.”

Additional Motus stations are planned for the other parks in Washington, as well as in California. There are already Motus towers in Golden Gate National Recreation Area and Point Reyes National Seashore, and more are planned for those parks. This fall, a Motus tower will be installed in Yosemite National Park, and still others are planned for Channel Islands National Park. In Washington and Yosemite, the focus is on studies that inform white-nose syndrome monitoring and management, while at other sites along the California coast, the data will inform planning for offshore wind energy.

Hoary bat held in gloved hand with a tiny Motus tag attached to its back
Hoary bat with a Motus tag.


Yosemite National Park: A Little Help from our Climbing Biologist Friends

About 700 miles south of the Washington parks, USGS and National Park Service scientists in Yosemite National Park are also keeping tabs on white-nose syndrome. White-nose syndrome has not yet been documented in California bats, but the fungus that causes white-nose syndrome, known as Pd, has been potentially detected at low concentrations at multiple locations in California in recent years, including just southeast of Yosemite in 2021.

Understanding the behavior and ecology of Yosemite’s bats will be essential for monitoring and protecting them as white-nose syndrome spreads. The scientists have started capturing and attaching transmitters to Yosemite’s bats with the goal of understanding where they roost in the summer, hibernate in the winter, and what these sites look like.

A Motus tower and transmitters are coming to Yosemite, but so far, they have been using VHF-transmitters to track the bats in Yosemite, a long-established tool in wildlife tracking. For this type of transmitter, scientists need to use mobile receivers that are carried by a person or mounted on a vehicle, and they must get fairly close to the tagged animals, walking or driving around with an antenna until they pick up the high frequency signal emitted by a transmitter. They can use these signals to narrow in on the locations of the bat roosts, and ideally, find the exact spot to visit and observe it.

A scientist holds out an antennae with the dramatic cliffs of Yosemite Valley in the background
Austin Waag performing radio-telemetry at Glacier Point with Half Dome in the background, as part of a project tracking bats in Yosemite National Park.

That’s not too difficult to do if a bat is close to the ground or a road, and to locate some of the roosts scientists have been hiking and driving around Yosemite’s beautiful landscapes with antennae.

"It feels like working in a postcard,” said Gabe Reyes, a USGS biologist who studies bats in Yosemite and several other California national parks.

But the most iconic features of this park are not so easy to access: sheer granite cliffs that extend thousands of feet up, forming the margins of Yosemite Valley and attracting rock climbers from around the world. Bats like these cliffs, too, and many roost sites are located high up in the rocks, making them very hard to reach.

That’s where the rock climbing biologists come in. It’s perhaps no surprise that some of Yosemite’s biologists and other collaborators are skilled rock climbers. With climbers on the research team, these roost sites are no longer inaccessible. The climbers carry antennae and video cameras with them to locate and document the hard-to-reach roost sites.

A rock climber on a rocky cliff looks down at another climber and the vegetation below
A climber above the valley floor in Yosemite searching for a bat roost as part of a study tracking bats and locating and describing their roosts, which can be high on Yosemite's cliffs.

“These are areas that are normally inaccessible to us,” said Reyes. “Partnering with the climbing biologists is opening up unique opportunities to learn about bat ecology.”

The research team documented roost sites in the fall 2021 and summer 2023. They had intended to study the bats as they entered hibernation at the tail end of the 2021 season, too, but there was a problem—the winter was mild and the bats hadn’t begun to hibernate by the time the study ended in December. The VHF transmitters didn’t last long enough to observe winter behavior later into the season.

Now the team is adding a new approach to the Yosemite project: Motus. The transmitters last longer, allowing them to track behaviors over longer periods of time.

“We're really excited about that potential, to be able to track bat activity patterns into the winter and deal with the challenge of not knowing when winter will start,” said Reyes.

And once a receiving station is set up in the park (one will be installed this fall), it will detect the transmitters automatically, and at greater distances. Instead of hiking and climbing all over the park to map bat locations, they will be able to remotely view the bat's approximate movement patterns over longer time periods, increasing the likelihood of observing winter behavior (they’ll still need to work in the park to capture the bats and attach transmitters and to document conditions at roosts and hibernation locations).

Scientists wade in shallow water as they set up a large mist net with the sheer cliffs of Yosemite Valley in the background
Biologists set up a triple-high mist net to capture bats with El Capitan, one of Yosemite's most iconic rock formations, in the background, as part of a study to track bats in Yosemite.

Grand Canyon National Park: And Our River Rafting Friends

Yosemite’s climbing biologists are just one example of how the rich opportunities for outdoor recreation offered by national parks can be harnessed for science. Bat biologists working in Grand Canyon National Park have been working with outdoor adventurers, too.

Landscape view of the Colorado River in the Grand Canyon with plants in the foreground.
The Colorado River in Grand Canyon taken from Grand Canyon Village, Arizona. 

While Yosemite is known for its rock climbers, the Grand Canyon has lots of river rafters. It also has lots of bats. Grand Canyon is a hotspot for bat diversity, with 22 species, more than any other national park unit. Deep in Grand Canyon, the Colorado River provides bats with drinking water and insect prey, and the canyon walls and plants growing along the river provide habitat.

“While it's intuitive to many people that aquatic insects are important to animals like fish, fewer people realize that aquatic insects are also really important food for other vertebrates like bats, frogs, lizards, and birds,” said Anya Metcalfe, a USGS ecologist working in the Grand Canyon.

As is the case with reaching bat roosts on the high rock walls of Yosemite, conducting research in Grand Canyon can be challenging. The river is deep, swift, and cold, and there are relatively few trails down into the canyon, so reaching field sites can require multi-day rafting expeditions. To access these remote sites, USGS scientists collaborate with river guides, private boaters, and educational groups. For a study published earlier this year, river rafters monitored bat activity using acoustic detectors and sampled insects using light traps, collecting a total of 1,428 paired bug and bat samples between 2017-2020.

Partners in Science trip participants deploy a light trap to sample aquatic insects along the Colorado River in Grand Canyon
Community scientists deploy a light trap to sample aquatic insects along the Colorado River in Grand Canyon.

“It has been amazing getting to know and collaborate with commercial river guides in Grand Canyon,” said Metcalfe. “They are incredible sources of knowledge and keen observers of natural history and change in the park.”

USGS scientists and partners then analyzed the data to explore what influences bat activity in the Grand Canyon, considering insect abundance alongside other factors such as time of night and time of year, temperature, vegetation density, river width, and distance from Glen Canyon Dam. They found that bat activity was primarily related to the availability of aquatic flies emerging from the Colorado River, suggesting that river management strategies that promote the production and diversity of aquatic insect assemblages will likely also benefit bat species that forage along the river.

“Grand Canyon National Park is a special place and this project has been a hub for connecting people who want to give back to the place by understanding it better,” said Metcalfe.

Across the United States, bats are contending with threats like white-nose syndrome, energy development, habitat loss and fragmentation, and climate change. Innovative approaches like the Motus network and collaborations with climbers and river rafters are helping USGS and National Park Service scientists and other partners gather data about bats at larger scales than ever before, providing new science to inform bat conservation.

A SM4 bat detector to record ultrasonic bat calls is deployed in Grand Canyon
A SM4 bat detector is deployed at Kwagunt Canyon in Grand Canyon. This weatherproof detector records ultrasonic bat calls. Photo by Anya Metcalfe, USGS, SBSC.

Learn More

Learn about USGS collaboration with NPS using Motus to study bats in Washington and Northern California

Learn about Motus tracking of birds and bats in Southern California

Read more about the Grand Canyon study

Safety Note: Bats and Rabies

Bats are known to carry rabies, which is a zoonotic disease that can be transmitted to humans and is fatal if untreated. Bats can spread rabies to humans through their saliva, via bites or scratches. It is important to never touch or handle bats, especially if they appear sick or are exhibiting unusual behavior such as being active during the day. Anyone who has had direct contact with a bat should seek medical consult, as rabies can only be confirmed through lab testing.

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