Here you have the largest and one of the smallest of New World bats: the great Vampyrum spectrum on the right and the tiny Vampyressa pusilla on the left.

Here's another view of the false vampire, Vampyrum spectrum. It's not a blood eater. It eats whole rats, parakeets, doves, and whatever else it finds at night on exposed limbs. I think nobody has seen it catching any of these things, but I think it must use its sonar and go along limbs at night picking these things off sort of like corn off the cob. This prey is a house rat, about the size of the bat.

Here is a really big bat, an Old World flying fox. It looks really big in this hanging posture all covered with its wings.

As you can divine by comparison with my thumbnail, this is one of the smallest New World bats. It's called the smoky bat, Furipterus horrens. When we caught this bat, we were elated because we hadn't recorded its ultrasounds previously. So we let it loose in our bedroom and turned on the ultrasound receiver to listen to it. We heard nothing. It was obviously echolocating because it would fly around the room, come to a corner, and hover as though it were really studying the features there. We turned the ultrasound recorder up to its maximum, over 200 kilohertz, and could barely hear the ultrasounds. This is the highest ultrasound frequency of any bat that we've encountered. The majority of bats, such as those here in California, are in the range of 25 to 45 or 50 khz, but this one is over 200. For comparison, ordinary human speech is in the range of 975 Hz to 5 kHz.

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