U.S. Joint Fire Science Program


Date of this Version


Document Type



Fire Science Brief, Issue 109, May 2010


US government work.


The spring prescribed burn window in the Central Hardwoods is short (usually April) and good burning days are few. The Daniel Boone National Forest (DBNF) prescribed fi re program is trying to regenerate oak ecosystems ahead of the arrival of gypsy moths in the region and the high overstory oak mortality that can result. If the burn window could be extended into the growing season (later spring), managers could control vegetation more effectively. However, the DBNF also serves as warm-season roosting habitat for the endangered Indiana bat, so burning into the growing season could potentially put the bats—and especially maternity colonies—at risk. Until now, no studies had been conducted regarding the risk to the bats from prescribed fire. Research was therefore needed to determine whether managers could burn later into the growing season without posing risk to the Indiana bat—and if so, how it should be done. The research shows that if bats are in torpor during a fire and cannot arouse quickly enough to escape, they may be harmed, and the risk of injury is directly related to fireline intensity. Fire’s heat poses risk to the bats, but fi re’s gases do not. Models of bat ear burns showed that the height up to which ear injury is likely to occur corresponds roughly to the height up to which crown scorch occurs, and thus fireline intensities should be kept low enough so that crown scorch height does not approach the mean roosting height of 30 feet or 9 meters. The research suggests that risk to bats from prescribed fire can be greatly reduced through a combination of various approaches: (1) using ignition tactics that reduce fireline intensity, (2) choosing appropriate burn season/weather, (3) using ignition tactics that cue bats to arouse from torpor and flush, and (4) ensuring large roost snags (and trees that will become snags) are available. The research team also found that fire improves foraging conditions in the year following fire by increasing prey abundance.