In this video for Science Friday, bat biologist Nickolay Hristov takes a thermal camera inside Carlsbad Caverns to see what bats do in the dark when nobody's watching.
In his footage, a blazing yellow blob on the cave ceiling—which the video's narrator likens to a pool of lava—is actually a mass of bats, packed closely together and hanging upside down. Here, Hristov can see, in person, the very social world of bats, playing out as though he weren't even there.
It's a great video, and well worth watching.
Via Science Friday
EDIT: Video embed is fixed and should work now.