Modeling Fog Oil Obscurant Smoke Penetration Into Simulated Tortoise Barrows and Bat Colony Trees

Abstract : The gopher tortoise (Gopherus polyhemus) and the Indiana bat (Myotis sodalist) are species found on many military installations. The Indiana bat is endangered throughout its range, and the gopher tortoise is threatened in its westernmost distribution and at risk everywhere else. On installations where troop readiness training is conducted, an important component of realistic troop readiness training is the generation of obscurant material and the conduct of maneuvers under obscurant cover. Fog oil has long been deployed for visual obscuration training, and the effect of such obscurants on these species is unknown. As a preliminary step prior to instituting toxicological studies, a laboratory simulation was performed of the capability of the fog oil smoke to penetrate the living space of these species, the tortoise burrow and the hollow-tree location of a bat maternity colony. The fog oil smoke did not enter the simulated tortoise burrow in significant concentrations, but smoke concentrations in the simulated tree cavity approached ambient levels. This suggests that tortoise burrows do not need to be studied in situ, and that tortoises may be considered protected while in the burrow. Bat maternal colony sites, however, should not be considered protected from smoke entry to any significant degree.