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METHODS &
SAMPLE DESIGN

NABat relies on a probabilistic, yet flexible sampling approach. Our protocols and guidance ensure data standards are integrated across the multiple lines of evidence that are employed to inform status and trends analyses of North American bats.

Photo: Melissa McGraw

The Protocol

consistent yet flexible

Bats have diverse and complex life histories and behaviors, making a 'one size fits all' approach to monitoring impractical. Our protocols were conscientiously designed with this in mind, providing clear but adaptable guidance for bat monitoring efforts in the U.S., Canada and Mexico.

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The Plan >​

The Master Sample

a probabilistic sampling approach

NABat monitoring follows a master sample approach in which North America is divided into a series of 10 x 10 km (100 km) grid cell frameworks. The generalized random-tessellation stratified (GRTS) survey design algorithm then assigns a spatially balanced and randomized ordering (GRTS order) to each cell within its respective framework. 

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Grid cells are prioritized numerically; the lower the number, the higher the sampling priority. Cells can then be selected for monitoring following the GRTS order, ensuring both randomization and spatial balance. Monitoring within this standardized framework allows statistical inference to non-surveyed locations and ensures the validity of analyses at regional and range-wide scales using data collected by dozens of partners across the continent.

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Master Sample >

Master Sample (Offshore) >​​

Survey Types

a weight of evidence

  1. Acoustic surveys along mobile driving transects

  2. Acoustic surveys at stationary point locations

  3. Roost emergence counts

  4. Internal roost counts

  5. Capture Surveys

  6. Transportation structure surveys

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Guidance >

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2018 by Bat Conservation International in partnership with the NABat Program

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