Foto und Montage: Axel Griesch

Research Group Acoustic and Functional Ecology

The Emmy Noether funded research group “Acoustic and Functional Ecology” investigates the functional and ecological principles of sensory processing and associated animal behaviour. We pursue these questions in the ecologically important context of predator-prey interactions, using echolocating bats and eared insects as model systems of auditory information processing and auditory-guided behaviour.

 

Sensory processes are at the centre of an animal’s perception of the world and its actions in this world, including some of the most crucial behaviours for survival such as foraging and predator avoidance. Accordingly, natural selection has not only shaped the morphology of animals, but also their sensory and behavioural properties. Our overall scientific objective is to understand the function of sensory systems and their consequences for ecological and evolutionary processes. In our research, we study bats and moths as two model systems for complex and simple auditory processing and auditory-guided behaviour.

Echolocating bats rely to a large extent on auditory information for orientation, foraging and communication. Bats are thus a great model system to study auditory processing and the adaptation of sensory processes to ecological requirements. In our research, we address questions of sound-based perception of the environment, the use of sound for inter-individual and inter-specific interactions, the importance of dynamic sensory processing for the perception of complex and variable auditory scenes, and effects of the environment, including climate change, on sound-based perception.

In contrast to the flexible sensory-motor system of bats, the ears of noctuoid moths are simple. They consist of only 1-4 auditory neurons and trigger a two-staged evasive flight response, consisting of directional and erratic flight to escape attacking bats. The well-studied neurobiology of the simple moth ear provides an ideal foundation for a systematic study of the evasive behaviour of moths, which is the phenotype selected by bat predation. Moth families differ in the number of auditory receptor cells (1-4 cells) and additional antipredator strategies. This allows to study the function and adaptive value of evasive flight and protean escape mechanisms in a comparative approach and to test biological hypotheses, for example on the risk-dependent evolution of erratic flight, sustained erratic flight without sensory input and phenotypic variability as adaptation to predation pressure.

Echolocating bats and moths with bat-detecting ears are tightly connected in an evolutionary arms race. Their predator-prey-relationship is solely based on acoustic information and auditory-guided behaviour for foraging and for predator avoidance, respectively. They interact with one another in a functional, ecological and evolutionary relationship, adding additional layers of complexity and interdependence. Our research addresses auditory processing and auditory guided behaviours on all these levels, from individuals to populations. They are thus a perfect and highly integrated model system to study auditory-guided flight at two extremes of sensory processing.

Moth species perform evasive flights with species-specific diverse tactics in response to the same simulated bat attack. This variability of evasive flights increases the population-wide unpredictability experienced by bat predators, likely protecting the whole moth community against their predators.

Each moth escapes its own way

Moth species perform evasive flights with species-specific diverse tactics in response to the same simulated bat attack. This variability of evasive flights increases the population-wide unpredictability experienced by bat predators, likely protecting the whole moth community against their predators.

Just published: Our research in the Research Highlights of the Yearbook 2018. Holger Goerlitz’s report about predator-prey-interactions for the Max Planck Yearbook 2018 was chosen as one of the 15 Highlights of the Max Planck Society 2018.

Highlights of the Max Planck Yearbook 2018

Just published: Our research in the Research Highlights of the Yearbook 2018. Holger Goerlitz’s report about predator-prey-interactions for the Max Planck Yearbook 2018 was chosen as one of the 15 Highlights of the Max Planck Society 2018.

The sonar system of bats exploits spatial information in a way similar to our sense of sight, despite the different anatomy of eyes and ears.

Hearing in 3D

The sonar system of bats exploits spatial information in a way similar to our sense of sight, despite the different anatomy of eyes and ears.

Where do bats go for dinner? Echolocating bats use the social information provided by the echolocation calls of other bats to find food. A large-scale field experiment shows that they integrate species identity, conspecific activity and prey abundance.

Ubiquitous use of social information in bats

Where do bats go for dinner? Echolocating bats use the social information provided by the echolocation calls of other bats to find food. A large-scale field experiment shows that they integrate species identity, conspecific activity and prey abundance.

White light and supposedly bat-friendly light colours like amber and red have negative effects on multiple bat species in caves and during emergence

Negative effect of light on cave bats

White light and supposedly bat-friendly light colours like amber and red have negative effects on multiple bat species in caves and during emergence

Most animals are at risk from multiple predators. In our new study in the Journal of Theoretical Biology, we combine empirical data and flight path modelling of a sympatric community of 12 moth and 14 bat species.
We show (1) that bat call frequency predicts bat predation threat, and
(2) that the simplest ears in nature exploit this relationship to trigger defensive evasive flight that is adapted to all bats in the community.

Simple ears solve complex problems

Most animals are at risk from multiple predators. In our new study in the Journal of Theoretical Biology, we combine empirical data and flight path modelling of a sympatric community of 12 moth and 14 bat species. We show (1) that bat call frequency predicts bat predation threat, and (2) that the simplest ears in nature exploit this relationship to trigger defensive evasive flight that is adapted to all bats in the community.

In our new modelling study in PNAS, we show that actively echolocating bats can still hear returning echoes, despite all the loud masking calls of their neighbours. The presumed cocktail party nightmare is thus rather a challenge than a nightmare. Bats detect echoes of their closest and frontal neighbours. This spatial limitation might even be beneficial for following their neighbours during emergence.

Bats can echolocate even in dense swarms

In our new modelling study in PNAS, we show that actively echolocating bats can still hear returning echoes, despite all the loud masking calls of their neighbours. The presumed cocktail party nightmare is thus rather a challenge than a nightmare. Bats detect echoes of their closest and frontal neighbours.
This spatial limitation might even be beneficial for following their neighbours during emergence.

Our research is featured twice: in the upcoming issue of MaxPlanckResearch, and with an interview of Holger in the new podcast of the “Forschungsquartett” (the weekly podcast of the Max Planck Society on detector.fm) about sound.

Read about and listen to Sound and Bats!

Our research is featured twice: in the upcoming issue of MaxPlanckResearch, and with an interview of Holger in the new podcast of the “Forschungsquartett” (the weekly podcast of the Max Planck Society on detector.fm) about sound.

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