By fitting bats with GPS collars we have discovered that the nocturnal fliers seek out slopes where late night winds are swept upwards, carrying them high into the air
Source:
https://www.newscientist.com/article/2266807-bats-soar-to-heights-of-1600-metres-by-riding-late-night-winds/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home