Short-term effects of wildfire on bat activity on the Valles Caldera National Preserve, New Mexico

Date

2015-08

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Abstract

Bats are important components of forested ecosystems. Most bat species depend on forest habitats for roosting or foraging, and are also beneficial to these forests (e.g., insect suppression). In the American Southwest, large and unprecedented wildfires are occurring more frequently as a result of anthropogenic disturbances. Wildfires weaken trees and stimulate flowering plant growth, attracting potential prey insects for bats. They also create roost sites and thin cluttered forests. However, severe wildfires may not provide these benefits for bats due to an increased impact on the trees and soil. The relationships between bats and forest fires are still not well understood. In particular, we have a limited knowledge of how large and severe wildfires may influence bats. The focus of this study is to determine how bat activity is influenced by wildfire, and more specifically, how burn severity and vegetation type affects activity levels in the years immediately post-fire, at a landscape-level scale. Acoustic surveys were conducted at the Valles Caldera National Preserve, New Mexico from June-October in 2013 and May-July in 2014 at four study sites within each of three treatments: unburned, the Las Conchas Wildfire (2011), and the Thompson Ridge Wildfire (2013). Six sites were randomly surveyed each night using SM2Bat+ Song Meters. The number of files recorded containing bat calls was determined for each study site for each night it was surveyed. Mean nightly bat activity levels for each site were correlated with proportions of burn severities and vegetation types around each study site using a series of buffers. Bats were found to be more active in burned areas than in unburned areas. Within burned areas, activity levels were higher in areas that burned at lower severities, and lower in those that burned at higher severities. Bats also tended to be less active in particular vegetation types, while being more active in others. A mosaic of burn severities and vegetation types across the landscape appears to be most beneficial for bats. These patterns are hypothesized to be a result of increased prey availability, but further analyses are needed to better understand these relationships.

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Keywords

Fire Severity, Wildfire, Bats, Chiroptera, New Mexico

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