500,000 Brazilian free-tailed bats fly out of a cave (video)

Using infra-red cameras:

From Wired

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"With the Hubble telescope and all the other things that are out there, I believe something would have come through. Today, I really believe we are unique." -Mark Goddard
The Wide Field Infrared Survey Explorer (WISE) has been all snapped together and stuff and is ready to be launched into outer space from Vandenberg in November.
Earlier this week, I showcased the newly-released Hubble Ultra Deep Field in the infrared, and compared it with the older image of the same region taken in visible light.

OK, that's very cool.