Estimation of spatiotemporal trends in bat abundance from mortality data collected at wind turbines.

Renewable energy sources, such as wind energy, are essential tools for reducing the causes of climate change, but wind turbines can pose a collision risk for bats. To date, the population-level effects of wind-related mortality have been estimated for only 1 bat species. To estimate temporal trends in bat abundance, we considered wind turbines as opportunistic sampling tools for flying bats (analogous to fishing nets), where catch per unit effort (carcass abundance per monitored turbine) is a proxy for aerial abundance of bats, after accounting for seasonal variation in activity. We used a large, standardized data set of records of bat carcasses from 594 turbines in southern Ontario, Canada, and corrected these data to account for surveyor efficiency and scavenger removal. We used Bayesian hierarchical models to estimate temporal trends in aerial abundance of bats and to explore the effect of spatial factors, including landscape features associated with bat habitat (e.g., wetlands, croplands, and forested lands), on the number of mortalities for each species. The models showed a rapid decline in the abundance of 4 species in our study area; declines in capture of carcasses over 7 years ranged from 65% (big brown bat [Eptesicus fuscus]) to 91% (silver-haired bat [Lasionycteris noctivagans]). Estimated declines were independent of the effects of mitigation (increasing wind speed at which turbines begin to generate electricity from 3.5 to 5.5 m/s), which significantly reduced but did not eliminate bat mortality. Late-summer mortality of hoary (Lasiurus cinereus), eastern red (Lasiurus borealis), and silver-haired bats was predicted by woodlot cover, and mortality of big brown bats decreased with increasing elevation. These landscape predictors of bat mortality can inform the siting of future wind energy operations. Our most important result is the apparent decline in abundance of four common species of bat in the airspace, which requires further investigation.

Estimación de Tendencias Espacio-Temporales en la Abundancia de Murciélagos a Partir de Datos de Mortalidad Recolectados Alrededor de Turbinas de Viento Resumen Las fuentes de energía renovable, como la energía eólica, son herramientas esenciales para la reducción de las causas del cambio climático, aunque las turbinas de viento pueden representar un riesgo de colisión para los murciélagos. A la fecha, los efectos a nivel poblacional de la mortalidad asociada a estas turbinas sólo han sido estimados para una especie de murciélagos. Para estimar las tendencias temporales en la abundancia de murciélagos consideramos a las turbinas de viento como herramientas para el muestreo oportunista de los murciélagos en vuelo (análogo a las redes de pesca), en donde el esfuerzo de captura por unidad (abundancia de cadáveres por turbina monitoreada) es un sustituto para la abundancia aérea de murciélagos, después de considerar la variación estacional en la actividad. Utilizamos un conjunto grande de datos estandarizados del registro de cadáveres de murciélagos alrededor de 594 turbinas al sur de Ontario, Canadá, y corregimos estos datos para justificar la eficiencia del muestreador y la extracción por carroñeros. Usamos modelos de jerarquía bayesiana para estimar las tendencias temporales en la abundancia aérea de los murciélagos y para explorar los efectos de los factores espaciales, incluyendo las características del paisaje asociadas con el hábitat de los murciélagos (p. ej.: humedales, tierras de cultivo y bosques), sobre el número de muertes para cada especie. Los modelos mostraron una declinación rápida en la abundancia de cuatro especies dentro de nuestra área de estudio. Las declinaciones en la captura de cadáveres a lo largo de siete años variaron desde el 65% (Eptesicus fuscus) hasta el 91% (Lasionycteris noctivagans). Las declinaciones estimadas fueron independientes a los efectos de mitigación (el incremento en la velocidad a la cual las turbinas comienzan a generar electricidad de 3.5 a 5.5 m/s), lo cual redujo significativamente la mortalidad de los murciélagos, aunque no llegó a eliminarla. La mortalidad a finales del verano de las especies Lasiurus cinereus, Lasiurus borealis y Lasionycteris noctivagans la pronosticó la cobertura de los lotes boscosos, mientras que la mortalidad de E. fuscus disminuyó conforme incrementó la elevación. Estos elementos pronosticadores del paisaje pueden utilizarse para informar al momento de elegir el sitio para la actividad eólica en el futuro y así evitar la mortalidad en murciélagos. Nuestro resultado más importante es la declinación aparente en la abundancia de cuatro especies comunes de murciélagos en el espacio aéreo, lo cual requiere de más investigación.

Timing and Weather Offer Alternative Mitigation Strategies for Lowering Bat Mortality at Wind Energy Facilities in Ontario.

Relatively high mortality of migratory bats at wind energy facilities has prompted research to understand the underlying spatial and temporal factors, with the goal of developing more effective mitigation approaches. We examined acoustic recordings of echolocation calls at 12 sites and post-construction carcass survey data collected at 10 wind energy facilities in Ontario, Canada, to quantify the degree to which timing and regional-scale weather predict bat activity and mortality. Rain and low temperatures consistently predicted low mortality and activity of big brown bats (Eptesicus fuscus) and three species of migratory tree bats: hoary bat (Lasiurus cinereus), eastern red bat (L. borealis), and silver-haired bat (Lasionycteris noctivagans). Bat activity occurred in waves with distinct peaks through the season; regardless of seasonal timing, most activities occurred in the first half of the night. We conclude that wind energy facilities could adopt a novel and more effective curtailment strategy based on weather and seasonal and nocturnal timing that would minimize mortality risks for bats while increasing the opportunities for power generation, relative to the mitigation strategy of increasing cut-in wind speed to 5.5 m/s.

Road avoidance and its energetic consequences for reptiles.

Roads are one of the most widespread human-caused habitat modifications that can increase wildlife mortality rates and alter behavior. Roads can act as barriers with variable permeability to movement and can increase distances wildlife travel to access habitats. Movement is energetically costly, and avoidance of roads could therefore impact an animal's energy budget. We tested whether reptiles avoid roads or road crossings and explored whether the energetic consequences of road avoidance decreased individual fitness. Using telemetry data from Blanding's turtles (Emydoidea blandingii; 11,658 locations of 286 turtles from 15 sites) and eastern massasaugas (Sistrurus catenatus; 1,868 locations of 49 snakes from 3 sites), we compared frequency of observed road crossings and use of road-adjacent habitat by reptiles to expected frequencies based on simulated correlated random walks. Turtles and snakes did not avoid habitats near roads, but both species avoided road crossings. Compared with simulations, turtles made fewer crossings of paved roads with low speed limits and more crossings of paved roads with high speed limits. Snakes made fewer crossings of all road types than expected based on simulated paths. Turtles traveled longer daily distances when their home range contained roads, but the predicted energetic cost was negligible: substantially less than the cost of producing one egg. Snakes with roads in their home range did not travel further per day than snakes without roads in their home range. We found that turtles and snakes avoided crossing roads, but road avoidance is unlikely to impact fitness through energetic expenditures. Therefore, mortality from vehicle strikes remains the most significant impact of roads on reptile populations.