Similarities in Design Features of Orientation Sounds Used by Simpler, Nonaquatic Echolocators

There are some remarkable similarities in the echolocation pulses of several species of nonaquatic echolocators that are relatively simple or conservative in terms of their echolocating abilities. I would like to illustrate this and offer speculations as to why this particular pattern of sounds has evolved repeatedly and, in many cases, independently. In the primary examples given, the echolocation signals consist of brief, unstructured sounds having a rapid onset and broad bandwidth. In addition, they often or always occur as paired pulses.