Marine Bioacoustics Lab

Huge congrats to Simone, Maja and Astrid, our three newly minted MSc experts on porpoise ecology & physiology and bat echolocation:)!

We have two exiting PhD positions on the topic of marine mammals and noise available with a May 1 application deadline:
https://phd.nat.au.dk/for-applicants/open-calls/may-2024/a-sound-marine-environment
Please share and apply:)

A sound marine environment Applications are invited for a PhD fellowship/scholarship at Graduate School of Natural Sciences, Aarhus University, Denmark, within the Biology programme. The position is available from August 2024 or later.

NEW PAPER: Porpoises conserve more oxygen when they can’t see!

The dive response of marine mammals allow them to undertake long breath-hold dives to access rich marine prey resources. It consists of a mixture of peripheral vasoconstriction and a lowering of heart rate, leading to lower metabolic rates in un-perfused tissues.
The dive response has been shown to vary with breath-hold duration, depth, exercise, and expectations during the dive. However, it is unknown to what extent sensory deprivation influences the dive response and oxygen management.
We show that acoustic masking causes very little change in heart rate of a trained harbor porpoise tasked with discriminating between two targets, whereas visual deprivation reduces heart rate by half of control values, suggesting a much larger importance of vision from these previously considered obligate echolocators. This indicates that such strong oxygen regulation in response to a change in sensory information could be a potential anti-predator response.

Check the paper out here: https://www.cell.com/iscience/fulltext/S2589-0042(23)00281-X #%20

How can echolocating toothed whale make 500 clicks per second with air at a 1000 meters depth where air volumes are compressed to less than 1%? How can toothed whales with the same nasal sound source produce both powerful, high frequency clicks for echolocation and softer, low frequency calls for complex communication?

Via long-term support from the Carlsberg Foundation and the Danish Natural Science Research Council, Coen, Ursula and I are happy to provide the answers to these long-standing questions a Science paper just out:
https://www.science.org/doi/10.1126/science.adc9570

Over the last 10 years, we developed and used several new techniques, ranging from in vivo endoscopy to in vitro preparations and acoustic tags on toothed whales in the wild.
We show that toothed whales possess a nasal sound production system driven by air. Loud clicks are made when phonic lips collide after having been forced apart by the airflow. This mechanism is functionally the same as laryngeal and syringeal sound production in other mammals and birds.

Acoustic analysis of calls across different toothed whale species shows that vocalizations are produced at different frequencies, consistent with tissue vibrations at different registers: just like human vocal folds.

The vocal fry register or M0 register makes powerful, high frequency echolocation clicks, and the two other registers make softer, more low frequency social calls for communication. For both sound types, air can be recycled, allowing for continued sound production during deep dives.

By combining all our methods, we show in freely moving animals diving as deep as 1800m that they use the vocal fry register for echolocation. The vocal register uses only very little air per click and unlocks the secret of how these apex predators can make the loudest biological sound pressure levels in the animal kingdom at depths of more than 1000 meters. This trick opened the previously unexplored rich food niches of the deep ocean for exploitation by more than 20 species of large toothed whales.

We dedicate our work to the late Dr. Sam Ridgway; a gentle scientific giant who pioneered so many scientific findings, including that toothed whales produce sound with their noses.