Auditory-guided behaviour at two extremes of sensory processing
Final Report Abstract
Decisions and actions require appropriate information. In a nutshell, in my research and Emmy Noether project, I strive to uncover the functional and ecological principles of animal sensing and acting in ecologically relevant contexts. Within each animal, sensing and motor behaviour form a tightly integrated closed loop, to achieve fitness-relevant behavioural goals such as finding food, attracting mates for reproduction, and avoiding and escaping predators. In addition, these individual-level sensory and behavioural processes interact across individuals, shaping their organismic interactions, their ecology and evolution. This is evident in animal communication, but also applies to the framework of my research, the interactions of predators and prey. Within split-seconds, predators and prey have to collect information, evaluate it with their nervous systems, and react accordingly in an adaptive manner. The actions of one contestant change the situation, the sensory input and the required actions of the other contestant. Therefore, from genes over cells to the ecology of organismal interactions, evolution has tightly integrated sensing and acting. I investigate sound as main carrier of information, which mediates the complex and diverse acoustic information network in the community of echolocating bats and different ear-possessing and acoustically communicating insects. I investigate the auditory processing of sound in these taxa, and their auditory-guided behaviours and organismal interactions. By comparing across species and between auditory processing and other sensory systems, I address fundamental functional and ecological principles in sensory physiology and behavioural ecology. I apply an integrative and comparative approach that combines neuroethological, bioacoustic and modelling approaches and behavioural experiments under controlled lab conditions and outside in the real world, to understand how animals obtain, process and exchange sensory information, how this information informs their actions, and how evolution has shaped sensory-motor processes to match ecological needs. These mutual organismal interactions of echolocating bats and eared insects generate diverse, complex and dynamic multi-species information networks, which exist everywhere on the planet, are of large ecological as well as economic importance, yet are still little understood. My research addresses four different interrelating research directions, focusing on Sensing and Perception in Individuals; how sensing and acting are adapted to and shape Predator-Prey-Interactions; how active sensing such as echolocation affects Communication and Interference in Dynamic Acoustic Information Networks; and how sensing deals with continuous Environmental and Anthropogenic Change and Variation. The here presented project on the predator-prey-interactions of echolocating bats and acoustically communicating bushcrickets investigates the sensory strategies of acoustically communicating prey species to defend against eavesdropping predators. This work exemplifies novel sensory strategies to prevail in the arms race between predators and prey. The first investigated prey species, the bushcricket Ruspolia nitidula, is unique in possessing previously unknown high-frequency ultrasonic components in its song. Due to the song’s uncommon acoustic characteristics of high frequencies, broad bandwidth, high intensity and fast repetition rate, it interferes with the echo-processing of bats and protects the bushcrickets from being captures. This project presents a courtship song that also functions as predator defences, explaining the lack of any other primary or secondary defences in the bushcricket R. nitidula. The special acoustic features of this song might have evolved through predator-mediated selection. The group singing behaviour of R. nitidula might provide additional protection to the singing males and potentially even commensal protection to other prey species. The second investigated species, the bushcricket Tettigonia viridissima, uses the common song cessation as secondary defence strategy against attacking bats. We show that song cessation is not a simple hard-wired response to any supra-threshold acoustic stimulus. In contrast, singing males evaluate detected acoustic signals to estimate the predation threat, and adjust song cessation to the perceived threat level and to their own remaining lifetime. In this way, they trade-off predator avoidance with mate attraction for reproduction, which will likely optimize their lifetime reproductive success.
Publications
- (2019): Acoustic Invisibility cloaks and pricked-up ears. / Akustische Tarnkappen und gespitzte Ohren. Scientific Highlights of the Max Planck Yearbook 2018 / MPG Forschungsbericht 2018
Goerlitz HR
(See online at https://dx.doi.org/10.17617/1.8I) - (2019): Insectivorous bats integrate social information about species identity, conspecific activity and prey abundance to estimate the costbenefit ratio of interactions. Journal of Animal Ecology 88(10): 1462-1473
Lewanzik D, Sundaramurthy AK & Goerlitz HR
(See online at https://doi.org/10.1111/1365-2656.12989) - (2019): Modelling active sensing reveals continued echo detection even in large groups of bats. PNAS 116(52): 26662-26668
Beleyur T & Goerlitz HR
(See online at https://doi.org/10.1073/pnas.1821722116)
