This is not a picture of a bat.
Sorry, I didn't see any bats flying around, though I heard them. It turns out that Western Mastiff bats (Eumops perotis) echolocate at a low enough frequency that you can actually hear them flying around looking for bugs. We scrambled up a ridge in a nature preserve and heard a bunch of them, but were never actually able to see them. Even with infrared binoculars! Eumops are the largest bat we get in North America, though that only means they're seven inches long. They roost in cliff crevices with enough room under them to be able to fall three meters in order to take off flying. In the desert you have to be careful where you walk, especially in the dark, in order to not step on the tarantulas.