The greater long-nosed bat, Leptonycteris nivalis, is federally listed as endangered in the United States and in Mexico. In the summer, adult females and their young migrate north from Mexico to Big Bend National Park in Texas, and to the southwestern corner of New Mexico. Migration is believed to be synchronized with the bloom cycle of agave plants, on which they rely for nectar and pollen. Our objective was to determine habitat use within the park. We hypothesized that bats would focus their activity in agave-rich areas.
In 2003, we attached radio-transmitters to 25 Leptonycteris nivalis and tracked nightly movement patterns in the vicinity of Emory Cave, the only known roost in Texas. Telemetry efforts were focused in the northern portion of the Chisos Mountains, due to heavy monsoon rains that limited access to the south and east. Simultaneous bearings from telemetry stations at high vantage points were used to estimate the location of bats throughout the night. Bats that had at least 25 locations were used to calculate 95% and 50% use areas.
Leptonycteris nivalis was found to use not only areas with known agave populations, but also spent time in areas of the park where no agaves or other known food sources have been reported. Additional research will be required to assess if the bats were using undiscovered night roosts, previously undocumented food resources, or perhaps simply exploring the landscape. The nature of the use will need to be determined before more detailed management recommendations can be made.