Echolocating bats face a cocktail party nightmare when they fly together in cluttered environments

Abstract

Echolocating bats often operate in the presence of conspecifics and in cluttered environments, which can be characterized as a “cocktail party nightmare.” Each bat's sonar vocalization can result in an echo cascade from objects distributed in direction and range. Adding to the acoustic clutter are the signals from neighboring bats. Past studies demonstrate that bats adapt their echolocation to avoid signal jamming from conspecifics by adjusting the frequencies of their vocalizations, as well as going silent. When bats fly alone in densely cluttered environments, they adjust the frequencies of call pairs to disambiguate overlapping echo streams. How do echolocating bats adapt to both conspecific signals and clutter? We sought to answer this question by flying big brown bats in a large room equipped with high-speed video and audio recording equipment. In baseline trials, bats flew alone in an empty room and were later introduced to an artificial forest, first individually and later in pairs. The echolocation behavior and flight paths are analyzed to evaluate the spectro-temporal adjustments of bat calls and silent behavior as animals progressed from open room, to forest, to forest with conspecifics. The results shed light on how echolocating bats adapt to a “cocktail party nightmare.”