Neural basis of echolocation in birds

Susanne Hoffmann, Alena Lemazina

Different groups of animals including vision-impaired humans use a biological sonar system (i.e. echolocation) instead of vision for navigation. They actively produce sounds and analyze the echoes reflected by surrounding objects to gain knowledge about the objects’ location, three-dimensional shape and surface structure. The only non-mammalian animals that are known to use biosonar belong to two avian groups, the Oilbirds, which are endemic to South America, and several species of Indoaustralien swiftlets. While biosonar behavior and its underlying neural correlates are widely investigated in bats and toothed whales, data on echolocating birds is rare. In contrast to the ultrasound signals of bats and whales, the sonar signals of echolocating birds are in a frequency range audible to humans, and the calls’ spectrotemporal structure is similar to that of sonar signals used by blind people. We combine bioacoustics and in-vivo neurophysiology to investigate how, and to what extent, echo-information is used by echolocating birds and how the information is processed in the birds’ auditory systems. In collaboration with Dr. Paolo Piedrahita (Escuela Superior Politécnica del Litoral, Guayaquil, Ecuador), we perform our experiments on wild Oilbirds in the Amazonian jungle of Ecuador. By uncovering similarity and/or difference between our data and existing data from research on echolocating bats, we hope to be able to describe echolocation mechanisms specific to certain groups or common to several groups of echolocators.