The origins and diversity of bat songs.

Singing plays an important role in the social lives of several disparate bat species, but just how significant the behavior may be among bats generally is unknown. Recent discoveries suggest singing by bats might be surprisingly more diverse and widespread than anticipated, but if true then two questions must be addressed: firstly why has singing been so rarely documented among bats, and secondly do bats sing for the same reasons as songbirds? We address the first question by reviewing how sampling bias and technical constraints may have produced a myopic view of bat social communication. To address the second question, we review evidence from 50 years of batsong literature supporting the supposition that bat singing is linked to the same constellation of ecological variables that favored birdsong, including territoriality, polygyny, metabolic constraints, migratory behaviors and especially powered flight. We propose that bats sing like birds because they fly like birds; flight is energetically expensive and singing reduces time spent flying. Factoring in the singular importance of acoustic communication for echolocating bats, it seems likely that singing may prove to be relatively common among certain groups of bats once it becomes clear when and where to look for it.