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Published on Jan 22, 2010
An hour or two before sunset at The Nature Conservancy's Eckert James River Bat Cave Preserve near Mason, Texas, hundreds of bats flutter and chirp around the mouth of the cave. Slowly, a stream of bats emerges and flies in a large circle, low to the ground, just outside the cave entrance. These bats gradually spiral upwards and form a dark funnel of flying mammals, reaching several hundred feet into the evening sky.