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Bats are essential parts of Earth’s environments and perform services valuable to humans. Research by USGS scientists shows that insect-eating bats—through their free pest-suppression services—save farmers at least $3 billion each year. Many bat populations are declining due to factors such as habitat loss and disease. Recent growth in wind-energy development brought the unexpected consequence of bat susceptibility to wind turbines. USGS science aims to understand and reduce bat fatalities and injuries at wind turbines through several integrated research strategies.

Screenshot from the "Can we make wind power compatible with wildlife" story map

Can We Make Wind Power Compatible with Wildlife?

This story is a case study on wind energy and bats in Hawaii that communicates the impact and value of USGS science to people and the environment. It focused on a portfolio of research that addresses the mortality of bats at wind energy facilities and describes the approach that USGS scientists are taking to develop “smart solutions” to help reduce the risks, as well as the costs, of domestic energy development.

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Each project below is associated with a type of energy production or transmission. Types of energy production or transmission are represented by the following icons:

Mining, Oil and Gas Extraction, and Wind Energy icons

Projects below also are grouped into the following categories:

Bat Migration and Distribution

Bat Behavior Near Wind Turbines

Bat Deterrents and Wind Turbine Operational Curtailment

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Bat Migration and Distribution

 

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Mid-Atlantic Coastal Bat and Acoustic Nano-Tag Study

Cooperative Research Unit: Virginia Cooperative Fish and Wildlife Research Unit

Scientists from the Virginia Department of Game and Inland Fisheries, USGS, and Virginia Polytechnic Institute and State University are studying migration timing and habitat use of eastern red bats in coastal areas of Virginia. With the move to develop coastal wind energy resources, there is a need to understand the potential for migration disruption and possible additive mortality of red bats and other migratory species. By understanding the timing of migration and offshore movements of these bats, it may be possible to design and implement wind energy mitigation measures, such as seasonal curtailment and (or) siting, to minimize interactions with bats. Eastern red bats along the coast of Virginia, Maryland, and New Jersey are being captured and outfitted with very high-frequency nano-tags. Fixed sensor towers capable of tracking multiple bats simultaneously have been placed along the Virginia outer coast and in the Chesapeake Bay. Initial results regarding nano-tag retention time and bat migratory movements are being analyzed.

 

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Modeling Foraging Habitat Suitability of the Hawaiian Hoary Bat

Science Center: Pacific Island Ecosystems Research Center

USGS and University of Hawai‘i at Hilo scientists are using thermal videography and echolocation sampling methods to more directly determine the occurrence and activity of the endangered Hawaiian hoary bat, a tree-roosting species. Previous approaches have relied solely on acoustic detection or bat capture, methods that have been inefficient for use in detecting sparsely distributed and vocally cryptic individuals at locations where encounter rates are low. Foraging habitat suitability is being related to bat occurrence, the frequency of feeding events, and insect abundance using multistate occupancy models, which can be more informative than simple models of presence and assumed absence. This approach may allow managers to evaluate the relative importance of different areas to foraging bats and track the effects of habitat restoration efforts over time.

 

Wind power, mining and oil and gas extraction icons

Post-White-Nose Syndrome Assessment of Bat Distribution in the Mid-Atlantic and Northeast

Cooperative Research Unit: Virginia Cooperative Fish and Wildlife Research Unit

USGS and Virginia Polytechnic Institute and State University, in cooperation with USFWS, the National WNS Program, NPS, U.S. Army, U.S. Marine Corps, Virginia Department of Game and Inland Fisheries, and National Council for Air and Stream Improvement are using multiyear acoustic data from more than 1,200 locations from the Appalachian Mountains to the Atlantic Coast, and from Virginia to New England, to determine post-WNS distribution and the community structure of bats. These data are being used to model current and future potential occupancy from the individual forest to landscape level. Results can be used to inform managers and regulators of the likelihood that a rare, threatened, or endangered bat species may be found in or near wind energy development, surface mining, or oil and gas development activities on public lands. This project can also provide information on the level of effort required for acoustic monitoring of the endangered Indiana bat and threatened northern long-eared bat.

 

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Pre- and Post-Hibernation and Migratory Activity of Bats in the Central Appalachians

Cooperative Research Unit: Virginia Cooperative Fish and Wildlife Research Unit

USGS and Virginia Polytechnic Institute and State University used fixed-site, long-term acoustical monitoring near cave systems and along mountain ridgelines and adjacent side slopes in Virginia and West Virginia to determine the timing of hibernation and migratory pulses for the endangered Indiana bat, threatened northern long-eared bat, and eastern red bat. Activities related to date, hourly wind speeds, and ambient temperatures are being analyzed to determine drivers of activity in autumn and spring. These data provide further evidence that operational mitigation strategies at wind energy facilities could help protect migratory bat species and could be used to inform siting decisions for proposed wind energy facilities to lessen the potential impacts on migratory bats that use Appalachian ridges as their primary migration corridors.

 

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The North American Bat Monitoring Program (NABat)

Science Centers: Fort Collins Science Center and Northern Rocky Mountain Science Center

USGS is the lead agency of a multiorganizational program called NABat, or the North American Bat Monitoring Program. NABat members work to better understand the ecological consequences of population decline and risks from continuing and emerging threats, such as white-nose syndrome and wind energy, on 46 species of bats common to Canada, the United States, and Mexico. NABat’s mission is to help resource managers and industry partners map bat distributions, better estimate extinction risk, and evaluate the effectiveness of conservation actions. USGS has developed online data management and collaboration tools for bat monitoring, including services for archiving pre-construction acoustic recordings collected at wind energy facilities. Presently, NABat monitoring data have been collected in 39 States and 10 Canadian Provinces. NABat participants include State and Federal agencies, universities and NGOs, as well as private industry (for example, Duke Energy). Newly developed resources include a protocol for processing acoustic data collected to monitor the impacts of energy development on bats and advanced statistical modeling procedures to interpret acoustic monitoring data for bat population status and trends.

 

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Using Genetic Tools to Examine the Biology of Summer-Roosting Indiana Bats

Science Center: Fort Collins Science Center

Wide-ranging populations of Indiana bats have declined by approximately half since 1967, when the species was listed as endangered under the Endangered Species Act. Recent advances in genetic techniques have made it possible to uniquely identify animals using DNA in mark-recapture studies. USGS research has shown that DNA can be extracted from Indiana bat fecal pellets collected beneath roost trees. It is now possible to determine the relatedness of Indiana bat-colony members using genetic information and to estimate population sizes using DNA. Accurate demographic and relatedness information can assist conservation managers in management and recovery of the Indiana bat.

 

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Using Weather Radar to Detect Bat Colonies in South Texas

Science Center: Wetland and Aquatic Research Center

USGS scientists, using weather surveillance radar data to quantify the stopover distribution of birds migrating through the GOM region, detected partial ring signatures characteristic of bat movements. The scientists determined these signatures represented bats emerging from roost sites located under bridges within 80 kilometers of the Corpus Christi, Texas, radar station. Ground surveys of 8 of the 11 identified possible roost sites determined that 7 of those sites were occupied by Mexican free-tailed bats and other bat species. This study shows the utility of weather surveillance radar for locating bat colonies and monitoring regionwide bat movements.

Bat collage

From left: Indiana bat (Credit: U.S. Forest Service). Northern long-eared bat (Credit: Steven Thomas, USFWS). Hoary bat found dead beneath a wind turbine (Credit: Paul Cryan, USGS). Mexican free-tailed bats exiting Bracken bat cave (Credit: Ann Froschauer, USFWS).

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Bat Behavior Near Wind Turbines

 

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Factors Associated With Bat Mortality at Wind Energy Facilities in the United States

Science Center: Geosciences and Environmental Change Science Center

Researchers conducted a synthesis of studies on bat collision mortality with wind turbines and found further evidence that collision mortality is greatest for migratory tree-roosting species, such as the hoary bat, eastern red bat, and silver-haired bat. Researchers reviewed 218 studies conducted at 100 wind energy facilities in North America. The amount of grassland near the facility best predicted and was inversely related to bat mortality; however, further representative sampling of wind energy facilities is required to validate this pattern. This synthesis is a resource that developers and resource managers can consider when determining the placement of wind energy facilities.

 

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Understanding and Reducing Bat Fatalities Associated With Wind Turbines

Science Center: Fort Collins Science Center

Migratory bat species that roost in trees, or tree bats, are disproportionately affected by wind turbines, in part because they appear to be attracted to these structures. USGS science has led to new discoveries about these species, such as the consistent patterns in which tree bats approach and interact with turbines at night. USGS scientists have also identified areas of the continent where mortality risk might be higher, such as the Great Plains, the Great Lakes region, and areas adjacent to coastal wintering areas. Currently, USGS scientists are using this new information about bat behaviors, seasonal distribution, and perception to develop efficient and effective ways of reducing bat interactions with wind turbines.

 

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Wind Energy Effects on Mexican Free-Tailed Bats

Science Center: Geosciences and Environmental Change Science Center

USGS scientists and collaborators at the University of Arizona are studying the interactions of Mexican free-tailed bats (MFTB) with wind energy facilities and how bat fatalities at wind energy facilities may influence pest control services provided by MFTB to farmers in the Southwest. Scientists are using seasonal distribution models of MFTB and a full life cycle demographic model as well as data about roost locations, known wind turbine locations and bat fatalities, and locations of cotton, corn, and sorghum crops to address this question.

Bat approaching turbine tower

Bat approaching turbine tower. (Credit: Paul Cryan, USGS. Public domain.)

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Bat Deterrents and Wind Turbine Operational Curtailment

 

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Comparing the Effectiveness of Acoustic Deterrents to Operational Curtailment in Reducing Bat Fatality

Science Center: Forest and Rangeland Ecosystem Science Center

Independent studies have shown that both operational curtailment and ultrasonic acoustic deterrents can be effective in reducing bat fatalities at wind energy facilities. A primary goal of this study, co-funded by the DOE, USGS, and Bat Conservation International, is to compare the costs and benefits of acoustic deterrents to operational curtailment. Fatality rates, when both curtailment and acoustic deterrents are applied singly and in combination, are being compared with fatality rates at untreated turbines to determine if one of these methods is more effective, if they are equally effective, or if they might act synergistically when employed simultaneously.

 

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Ultraviolet Illumination as a Means of Reducing Bat Activity and Risk at Wind Turbines

Science Center: Fort Collins Science Center

Insectivorous bats are known for their ability to find and pursue flying insect prey at close range using echolocation, but they also rely heavily on vision. Using a cue that only bats would perceive, the USGS is developing technologies to prevent bats from approaching wind turbines that might be mistaken for trees. USGS scientists are collaborating with the National Renewable Energy Laboratory through a DOE Technology Development and Innovation award on refining a selectively perceptible wind turbine system to prevent bat fatalities. This project plans to test the hypothesis that dim, flickering, and position-shifting UV light can enable bats to differentiate turbines from trees, keeping bats from approaching turbines in search of resources such as food or roosts. Results from this and related research may determine whether dim UV light can reduce bat activity and fatality at operational wind farms, with the potential benefit of allowing operators to run turbines at maximum efficiency.

 

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Wind Turbine Curtailment Strategies to Reduce Bat Fatality

Science Center: Forest and Rangeland Ecosystem Science Center

Wildlife fatalities due to collisions with wind turbines have sparked efforts to reduce the number of fatalities through operational management. Recent studies have shown that altering turbine operations when winds are below certain speeds can decrease the number of bat fatalities, but questions remain regarding optimal management. USGS and colleagues are modeling the proportion of bat fatalities occurring under varying meteorological conditions at Avangrid Renewables’ Blue Creek Wind Farm in Ohio to identify conditions that minimize both bat fatalities and energy production loss. USGS scientists are also investigating whether accurate and precise estimates of fatalities can be derived from carcass searches conducted at easily accessed areas, such as roads and pads beneath turbines.