Ponderosa pine forests in the southwestern U.S. have increased in density over the last 100 years which has dramatically increased the size and frequency of wildfires. Although wildfires rarely kill animals, they have immediate consequences to bat populations by drastically altering vegetation and thus roosting and foraging opportunities. Because no studies in the Southwest documented effects of wildfire on bats, we examined how the bat assemblage responded to changes in vegetation structure and described roosting habitat used by reproductive female bats. Our study was conducted 2 and 3 years following the 538,000 acre Wallow Fire that burned in eastern Arizona in 2011. We used mist-netting at water sites and acoustic sampling throughout the Wallow Fire to address our objectives and collected data from June to August in 2013 and 2014. Three years post-wildfire, species richness was lower at water sites surrounded by high-burn severity (>50% basal area removed) compared to low-burn severity. In low-burn severity areas where ≤50% basal area was removed, call rates were highest for slow, maneuverable bats that echolocate at high-frequencies (>30 kHz). In high-burn severity areas, call rates were highest for bats that echolocate at low-frequencies, are fast fliers, and use open-air hawking. Ponderosa pine snag roosts (n = 50) located for 6 bat species were larger in diameter, with peeling bark, more decayed, and with less bark remaining on the snag compared to randomly-selected snags. Bats used snags with up to 100% bole burn, although one species, Arizona myotis (Myotis occultus), selected ponderosa pine snags with less burn (18% bole burn). The bat assemblage appeared to be declining over time and thus in this short-term study, wildfire appears to be having a negative temporal effect. Some species may adapt to temporal changes caused by wildfire but others that appear sensitive to high-severity fire, like the Arizona myotis, may not. Species that use fire-killed trees will encounter a pulse of roost structures for up to 10 years post-fire until snags fall; it may then take hundreds of years for forests to provide snags large enough for bat use. In the long-term, habitat for bats will decline if we cannot manage forests to reduce large, high-severity wildfires in the Southwest.
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