October 20, 2025As River Partners Associate Restoration Scientists Claudia Delgado and Diego Garcia drove among the sprawling alfalfa fields at Island Dairy, our 480-acre future restoration site in Stanislaus County, the sun was peeking over the horizon. They were out there to gather a few pieces of equipment, and after less than 10 minutes of driving on a single-lane vehicle access road, they reached their first of three destinations for the day.
Clamped to the top of a 12-foot-tall telescoping extension pole is what Delgado and Garcia came to get: A non-descript green-gray box measuring 3-by-5 inches. Visible among the contents inside were an on-off switch, eight AA batteries, and an SD memory card—the data on this SD card is what they were really after.
Deepening its commitment to learning more about wildlife that live in and around our restoration sites across the state, River Partners is now looking more closely at an animal community it never has before: bats. At eight different sites across two counties in the Central Valley, River Partners deployed 24 autonomous recording units (ARUs) to monitor bat activity this summer. For 30 nights, data was captured by ultrasonic microphones and saved on the SD cards in the bat monitors.
As a component of our ongoing Before-After Control-Impact (BACI) research, River Partners deployed three ARUs each at four future restoration sites and four nearby previously restored sites in Merced and Stanislaus counties. The bats’ calls and buzzes (called echolocation), sounds that are often outside the range of human hearing, were all captured digitally.
Thanks to valued collaborations with project partners Bat Conservation International (BCI) and Conservation Metrics, Inc. (CMI), as well as the California Wildlife Conservation Board which funded this project, River Partners is poised to learn more about bats and how they use our sites, without ever laying eyes on them.
So Many Bats, So Much to Learn
Aside from rodents, bats are the most species-rich group of mammals on our planet. There are around 6,500 known mammal species on our planet, and 1,500 are bat species—one in four mammal species on Earth is a bat.
So, why do we know so little about bats and, more specifically, how they use our Central Valley restoration sites? For starters, bats are more active at night when we don’t generally see them.
“They are often really cryptic species—they’re small, they fly at night, and we don’t see them very easily,” said River Partners Restoration Ecologist Ashley Verna, adding that time-tested methods of studying bats are very invasive (like scientists catching them in mist nets, studying them, then releasing them). Now with advances in technology over the last decade, the techniques have given way to much less invasive methods like recording their echolocations digitally.
Echolocation is used by animals, such as bats, as they navigate a space (sometimes in complete darkness) and hunt for prey, by emitting pulses of sound and using the returning echo to locate objects in their surroundings. After River Partners downloaded the content from the SD card, the recordings were sent to CMI, which uses specialized software to identify different characteristics of the echolocation calls to determine which species made them. Each bat species has its own unique sound signatures. BCI then visually reviews a subset of the recordings to confirm accuracy of the species identification. These acoustic data then move on for statistical analysis to see if bat activity and foraging are affected by restoration.
This cutting-edge science expanded our breadth of data on bats in the Central Valley and has helped form alliances within the conservation realm. For example, the results of the acoustic processing will not only benefit River Partners and the landscapes and communities we work in, but it will also contribute to bat conservation on a continental scale. The data will be submitted to the North American Bat Monitoring Program (NABat), a coalition of scientists, resource managers, and bat enthusiasts led by the U.S. Geological Survey (USGS) that collaboratively monitor bats, assembles data in a centralized database, and delivers status and trends for bats across our continent.
“It’s critical that we work together toward the common goals of conservation and a healthier planet,” BCI Conservation Research Coordinator Jessie Bunkley said. “While BCI is focused on bats, they are connected to everything else within an ecosystem, so the work we do to support and protect bats also benefits native plants, birds, insects, and other wildlife.”
CMI Project Manager Kerry Dunleavy, part of the team that is analyzing echolocation calls in this project, noted that having and sharing findings about bats will increase the value of restoration River Partners is undertaking around the state.
“When you’re doing the kind of restoration River Partners is doing, the more taxa, the better,” Dunleavy said. “For example, River Partners is doing a lot of bird work, but learning more about bats provides an entirely different glimpse into conservation we don’t have yet.”
River Partners will share the data, analysis, and knowledge we receive from BCI and CMI with other key project partners, including the California Department of Fish and Wildlife, U.S. Fish and Wildlife Service, and WCB.
“I think the reason why this work specifically is so vital is that we don’t currently know what the real range of some of these bat species is,” Verna said. “Any level of data collection we have and share with our partners can really contribute to the overall goal of science and data collection on these species.”
This ethos is at the heart of River Partners’ work.
“When you go to school to be a wildlife biologist, I think one of the biggest goals is to make a positive impact in your lifetime and contribute to the conservation and life improvement of wildlife as a result of your work,” Verna said. “That’s one of the things River Partners can do with this project—not hold on to the data but instead share with agencies to contribute to a bigger picture. That is such an important factor and River Partners goes out of our way to make sure we do that.”
Deeper Understanding of Bats
Much of what will be captured in this project will be used as baseline data for River Partners. Bats haven’t previously been included in this type of assessment before, so most of the rich results about future project design will come from repeating this work after more projects are implemented over time.
“If we only sample after this project is completed, how will we know if it was the restoration that benefited bats,” River Partners Associate Director of Restoration Science Emma Havstad said. “This is a necessary first step, but by no means the end of this effort.”
Additionally, River Partners will get a sense of how bats used sites that we plan to restore and ones we already have. This is included in our BACI research and will allow us to better compare vegetation composition and structure to bat presence and behavior between locations.
“Maybe we’ll find that the sites with the tallest cottonwoods have the most bat activity or maybe we’ll find that those with dense herbaceous cover are where the bats are most actively feeding,” Havstad said. “From that, we might infer something about the vegetation components that benefit bats and design our restoration projects accordingly.”
Inside remnant forests that haven’t been actively managed for a very long time, there are various known-age restoration stands. This variety will allow River Partners to compare how vegetation succession might influence bat community composition, abundance, and behavior.
“The different restoration ages also help us understand when to expect certain bats to show up in new restoration sites so that we have a better understanding of when to sample and when to expect ‘success,’” Havstad said. “These are living, dynamic systems that we’re building, and they’ll continue to change long after we stop treating weeds and irrigating.”
Learning by Listening
To know more about how to help bats in the Central Valley, it’s valuable to learn more about how they live—this begins by listening. Bunkley said that echolocation is an active sensory system, and bats change their calls as they change their behavior.
“If they’re flying through an open field, their calls will look different than if they are navigating through a space with a lot of objects, like forests or urban areas,” she said. “And their calls changes as they go in to capture an insect.”
These hunting calls are a “feeding buzz,” extremely fast echolocation calls so that a bat can home in on an insect that is trying to avoid being their dinner.
The ARUs for this project were set up for approximately 30 days—a full lunar cycle—which Verna said was important to document any behavioral changes in the bats, as well as insects they hunt.
“Different species of bats have been documented to reduce their activity during a full moon, commonly called lunar phobia. It will be interesting to see if any of the species documented will follow that pattern and what their lifestyle strategy is: are they predators or prey?” Verna said. “It’s only a month, but it’s a month more than what we had before. We’re hoping that the data we share will help to get us more attention which will help with funding future data collection.”
And while River Partners hopes a 30-day project is just the beginning, we also hope to help counter any misconceptions people have about bats because of their mysterious, nocturnal lifestyle. Bunkley notes that bats have very distinct personalities, much like other beloved animals close to home.
“People with pets know that not all dogs or cats are the same. There may be tendencies within breeds, and that’s the same for bats,” Bunkley said. “Each bat is an individual, living their life, with unique temperaments. It’s important to understand the science at the population level, because that informs conservation decisions, but it’s also valuable to appreciate the individual and recognize that we’re all experiencing the world through our own eyes and ears, and the same goes for bats.”
“It’s All Tied Together”
Bunkley believes that personal experiences with bats, like watching them emerge from a cave or hearing an acoustic detection, can add to our understanding of how connected we all are.
For example, nearly all U.S. bat species are insectivorous (they eat insects) and evolved alongside the native plants that support native insect populations. As a result, bats are crucial to maintaining ecosystem balance—and that includes pest control. In November 2024, Forbes magazine cited a study that said the economic value of bats to agriculture in the United States reaches into the billions of dollars.
“Bats are the number one predator of nocturnal insects, and many of the insects they eat each night are agricultural pests,” said Bunkley. “Their consumption of insect pests, like the cotton bollworm moth, saves farmers over $3.7 billion annually through reduced pesticide use and crop loss by insect damage.”
While River Partners learns about what helps bats thrive, we also hope to gain more knowledge about what can harm them, like white-nose syndrome (WNS), a fungal disease that’s unique to bats and is spreading rapidly westward across the country. The fungus spreads mostly through bat-to-bat contact, which concerns bat conservationists due to the close quarters in which bats live and hibernate.
The fungus grows on the bats’ skin, notably their noses, ears, and wings. It disrupts their hibernation patterns, which depletes their energy reserve and fat stores, and leads to dehydration and weakened immune systems, making them more susceptible to other infections. In 2021, the USGS reported that WNS killed more than 90% of the population of three North American bat species.
As of October 2024, WNS has been confirmed in five California counties (Humboldt, Sutter, Placer, Amador, and Inyo) and evidence suggests the fungus may be present in Trinity, Siskiyou, Shasta, Plumas, Alpine, San Diego, and San Bernardino counties, though these results remain inconclusive.
Whether it’s learning more about which bat species live in the Central Valley, getting a clearer picture of how they interact in this local ecosystem, or how conservationists can halt the spread of a deadly fungus, River Partners is moving forward in our understanding of one of the most diverse and least understood groups of mammals on Earth.
What we learn from this research will help us design our future projects, so we maximize benefits for all wildlife, including bats. And any lessons learned here happen only thanks to our close and valued partnerships.
“It’s really fun being a part of projects like this one with River Partners, where they’re doing the restoration work and are interested in seeing the impacts on the ecology,” Bunkley said. “They know that bats are one piece of the larger ecosystem puzzle and there won’t be any bats if we don’t have insects and plants to support them—it’s all tied together.”
