Migratory Corridors and Habitat Use by Bats Across Nebraska

USGS Cooperative Research Unit Corner

Migratory Corridors and Habitat Use by Bats Across Nebraska

The Nebraska Cooperative Fish and Wildlife Research Unit, in collaboration with state partners, is assessing the use of migratory corridors and habitat use by bats across the state of Nebraska in three linked projects. Specifically, the Nebraska Unit is investigating the distribution and habitat use of northern long-eared bats, identifying bat migratory patterns, and establishing the Nebraska portion of the North American bat monitoring program. The projects will provide important new information to understand Nebraska's bat species.

Bats provide valuable ecosystem services, primarily in the form of insect control. Recent studies suggest that the pest control services by bats are worth at least $1 billion dollars to the world corn industry and $3.7 billion to U.S. agriculture annually. Additional value is thought to lie in cascading effects, forest pest management, and disease vector reduction. However, catastrophic population declines threaten many bat species.

White-nose syndrome, a fungus that disturbs hibernating bats, kills more than 90% of bats in infected caves. First found in New York during 2006, the disease was estimated to have killed over 5.5 million bats by 2012. In 2016, WNS had spread across the eastern U.S. to 28 states and 5 Canadian provinces. The fungus that causes the disease has continued to spread rapidly across the continent and was detected in Nebraska in 2015 and Washington State in 2016. Declines related to these threats have led to the listing of the northern long eared bat as threatened under the Endangered Species Act, and petitions to list other species.

Although solitary migratory bats that do not use caves are thought to be safe from WNS, wind turbines pose a threat to these populations. Bats are seemingly attracted to wind turbines during migration and killed by the rapidly rotating blades. Turbines in the U.S. are estimated to have killed 650,000-1,300,000 bats between 2000 and 2011, an average of 1-40 bats per turbine.

The increased concern about bat populations has led the Nebraska Cooperative Fish and Wildlife Research Unit to initiate several projects to monitor bat populations across the state. The projects use acoustic monitoring to document bat activity at sites by recording the echolocation calls of passing bats. These calls are classified to species and provide presence, absence, or activity levels of bats at specific sites.

The Nebraska Department of Roads funded a study to investigate the distribution of the northern long-eared bat throughout the state and habitat associations where it does occur. The study will provide insight regarding distribution and habitat use to improve management and conservation of this declining species. During the first year of the study (2015), nearly 400 acoustic sites were sampled for six nights each in order to determine the distribution of the species throughout the state. This summer, intensive sampling within the known range will provide insights into the habitats that the northern long-eared bat uses in areas that have not been previously studied.

In order to understand the potential impacts of the rapidly expanding wind energy development in Nebraska, the Nebraska Unit is also conducting a project to examine where and when migration occurs within the Platte and Missouri River valleys. Very little is known about migratory bats, in fact, the wintering grounds of hoary bats remain unknown. Bats are thought to use landscape features during migration to aid in navigation. Therefore, the research team deployed bat detectors systematically across the river valleys and surrounding landscape between April and November. By examining the activity of bats throughout the year, researchers hope to identify migratory patterns related to weather and landscape features. The information will be used to inform siting and operation of wind turbines throughout the region.

The Nebraska Game and Parks Commission has funded a project to begin the North American Bat Monitoring program (NAbat), a continent wide population monitoring effort initiated by the U.S. Forest Service. Very little population information exists for bat species, and the program is a first of its kind to monitor populations across their range. The NAbat design includes both stationary acoustics and acoustic driving transects across the state. The Nebraska Unit will design the state program and conduct sampling in 2016. The hope is to transition to a citizen science program by 2018. The initial data will be used to describe species distributions and conduct power analysis for the monitoring program. Additionally, tools will be developed to guide the implementation of NAbat across the Midwest and Great Plains.

Nebraska has taken a proactive approach to learn more about their bat species, before devastating effects of WNS and wind turbines affect populations. These statewide projects are only possible with the participation of private landowners. More than 90% of acoustic sampling has been conducted on private lands. Nebraskans have been highly engaged and supportive of the collaborative research being conducted and have proven to be a valuable partner in protecting bats.

Data analysis of the over 3 million bat calls already recorded is beginning to reveal patterns in distribution and activity. As results of these projects are interpreted, the research team hopes to shed light on bat ecology in the Great Plains, an area where many questions about bat ecology remain.

The ONB features articles from Cooperative Fish and Wildlife Research Units across the country. Working with key cooperators, including WMI, Units are leading exciting, new fish and wildlife research projects that we believe our readers will appreciate reading about. This article was written by Craig Allen, Unit Leader at the Nebraska Cooperative Fish and Wildlife Research Unit.

July 14, 2016