Last updated: December 20, 2023
Article
Automated Radio Telemetry Will Shed Light on Olympic's Bats
USGS Photo/Hansen
SEPTEMBER 2023
Three miles past where the gates are swung shut to vehicles, beyond where the road has been washed away by floods, towers the concrete remnant of a vanished dam. Since the Glines Canyon Dam in Olympic National Park was removed in 2014 as part of the historic Elwha River restoration, the remaining spillway has offered a sweeping view over the former reservoir.
It's on this monument to the river’s return that scientists are mounting a new piece of equipment to help solve a stubborn mystery.
“We really don't know what happens to bats in the winter here,” said wildlife biologist Dr. Rebecca McCaffery, who leads the US Geological Survey’s Olympic Field Station in Port Angeles and is co-leading this research.
That’s a problem, because winter is when bats are at greatest danger from white-nose syndrome. This disease is caused by a fungus that attacks bats during hibernation. White-nose syndrome (WNS) was first observed in Washington in 2016, and at least 150 cases have been seen across the state since then.
In regions of the country where bats hibernate together in large groups, entire overwintering colonies can become infected and suffer massive losses. In the Pacific Northwest, however, many bats are solitary or hibernate in small groups. Some species depart in winter for parts unknown, while others may remain active throughout the cold months. Still, much of our understanding of winter bat activity here is uncertain due to the difficulty of tracking individual bats across long distances or periods of time.
“We just don't know how the disease is going to spread through the populations out here,” said McCaffery. “There are healthy colonies out there, but we know the disease is nearby. Are there places in North America where white-nose is going to be less of a big deal to bat health than others? Or will we begin to see big declines as the disease becomes more widespread in our region?”
A Global Network
On a sunny but chilly day in late September, USGS scientists working in partnership with the NPS were in the process of installing a solar-powered array of radio antennae to the side of the spillway structure. This is the newest receiver in a network of over 1,700 similar stations—all to observe a phenomenon that takes place on a global scale. Called the Motus Wildlife Tracking System, it takes its name from the Latin word for movement.
motus.org/data/receiversMap
“Motus towers are these stationary towers that have been set up all over the world,” explained McCaffery. Coordinated radio telemetry means that any Motus receiver can detect the signals send by tiny transmitters known as “nanotags.” Migratory bats at the former Lake Mills reservoir will be captured and fitted with unique nanotags, allowing them to be detected by any other Motus tower they pass on their migration. In other words—the bats move, but the towers don’t.
While this system was initially conceived for tracking birds, today over 320 species of bats, birds, and even migratory dragonflies and butterflies have been studied using Motus. By joining the network, Olympic becomes part of a global effort to understand animal movement: other migrants a long way from home may be detected here, at the Glines Canyon Dam.
However, not all Olympic’s bats are migratory, and researchers also hope to better understand the secretive habits of year-round residents through this study. “The idea of this project is to be able to use the Motus tower to understand the frequency and duration of their movements during the period of the year that they move into winter roost sites,” said McCaffery. “So they could go hide under some bark for three days and come out, and the tower would detect them.”
USGS Photo/McCaffery
Just One Piece of the Puzzle
Ever since WNS arrived in Washington, parks in the North Coast & Cascades Network have ramped up work in collaboration with the USGS to monitor and understand our native bats. Six parks—Mount Rainier, Olympic, North Cascades, San Juan Island, Lewis and Clark, and Ebey’s Landing—host permanent acoustic recorders, special units that pick up ultrasonic bat calls which can later be analyzed to identify the species and behavior.
In a separate study, USGS and NPS researchers placed acoustic recorders along transects from low-lying valleys up into the mountains of Olympic, Mount Rainier, and North Cascades. Over two years, the devices picked up activity from all ten resident bat species, allowing researchers to analyze how each species uses habitat at different elevations throughout the year.
As the fungus that causes WNS continues to spread in Washington, scientists work to detect any potential outbreaks early. Each spring, researchers test bat colonies in Olympic, Mount Rainier, North Cascades, and San Juan Island for the fungus.
In Mount Rainier, scientists keep close tabs on several bat colonies, including one that tested positive for the fungus in 2017. In collaboration with local partners, NPS scientists use lightweight metal bands on bats’ forearms to identify individuals. On repeat visits, recapturing previously banded bats can offer a snapshot of the colony’s health. The scientists also collect tissue samples to evaluate how genetics might be linked to survival.
NPS Photo/Chestnut
The launch of this project at Olympic represents yet another means to understand bat behavior—knowledge that park managers could use to help promote resilience to WNS in the future.
Seen from the new Motus station at the Glines Canyon Spillway Overlook, the broader story of the returning Elwha River comes into focus. In the river below, Chinook salmon swim upstream to spawn and perish, enriching creeks where dippers have made a rebound over the last decade. Bats emerge at twilight above the young forest of cottonwood, alder, and willow in the lakebed. As fall turns to winter, the antenna array will be busy picking up radio blips from bats that pass by or roost within range, beaming that information directly to the Motus database via the cellular network. Night by night, this ecological mystery will begin to crack.
“As a wildlife biologist, it’s exciting to study the natural history of something and to realize—oh my gosh, these common species are everywhere, and we don't actually know that much about them!” said McCaffery. “And this work is just one piece in the puzzle to understand how and where disease will impact these bats and what we can do about it.”