Mortality in big free-tailed bats, Tadarida molossa, led to investigations which resulted in collecting 61 of these bats, 2 spotted bats, Euderma maculatum, and other species. Bats were captured in mist nets over water. T. molossa flew at air temperatures as low as 55? F; young were generally captured earlier in the evening than adults. Individuals of this species flew at an elevation of 25 feet, singly or in groups of two or three. They flew in light rain and in less inclement weather and appeared to be attracted by captives of the same species. Euderma maculatum were captured when air temperatures were 58? and 64?. The rectal temperature of a resting spotted bat approximated its environmental temperatures, and the bat became torpid [...]