Flight Patterns of Bats

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Abstract
The time of the evening emergence and return of Tadarida brasiliensis mexicana is correlated with light conditions. The average emergence time was 11 minutes after sunset. Emergence was earlier on cloudy evenings. A literature search revealed three annual emergence patterns in bats: (1) species without seasonal differences in emergence time in relation to sunset, (2) species which leave relatively later in the spring and fall and (3) species which emerge relatively earlier in the spring and fall. Feeding flights of Tadarida were either diffuse where there was little group integrity or serpentine where the bats flew in a column. Serpentine flights occurred earlier in relation to sunset than did diffuse. The average time away from the cave was 3 hours 48 minutes. Calculations based on measured flow rate and flight duration indicate that all bats in a large population cannot leave the cave each night.