Roost and foraging associations among Mexican free-tailed bats (tadarida brasiliensis mexicans)

Radiotelemetry was used to tag groups of lactating adult Mexican free-tailed bats (Tadarida brasiliensis mexicana) in Texas nursery colonies. The existence of stable roosting and foraging associations was investigated. The presence of such groups was used to further explore how natural selection is operating to maintain communal nursing among adults in these caves.

Although individuals seem to show some roost site fidelity, there is no evidence that stable roosting groups exist. Nor is there any evidence of stable foraging associations among these bats.

Environmental variables were measured, and correlated with both the time and compass direction of the bat column as they depart for their evening foraging flight. While no significant correlations were found with departure direction, a number of variables were significantly correlated with the time bats leave the cave. Column departure time seems to be cued by lunar changes, the amount of cloud cover, and the windspeed.