Marine Bioacoustics Lab

28/06/2024

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

18/04/2024

Thanks to the best audience:)

🤸 Menneskedyret Homo sapiens er en fascinerende og kompliceret skabning - og sikken en evolutionshistorie der ligger bag den verden, vi kender i dag 🤯

Tak til Peter Teglberg Madsen for vidende og humoristisk at kortlægge, hvor vi kommer fra, og hvordan vi er blevet til nutidens mennesker. Du kan følge Peters forskning hos Marine Bioacoustics Lab 🤓

Dermed slutter vores forårssemester. En stor TAK fra os ved Aarhus Universitet skal lyde til forelæserne og de mange værter, som lægger hus til livestreaming tirsdag efter tirsdag 🙏 Tak til Carlsbergfondet for støtten - og tak til alle jer publikummer, der møder op gang på gang for at dele vores interesse og begejstring for naturvidenskaben 🥳🙌

Vi vender stærkt tilbage igen i efteråret - følg med i vores nyhedsbrev og på de sociale medier for høre mere, så snart vi er klar til at offentliggøre det kommende program 📢

05/04/2024

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:)

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.

01/03/2024

Congratulations to Dr Michael Bjerre Pedersen who brilliantly defended his PhD thesis titled Biosonar Performance in Echolocating Bats on Feb 28th. Michael has brought us several steps further in understanding the exceptional sensory capabilities in bats and their biosonar resilience when echolocating in challenging conditions.

28/06/2023

Large rorqual baleen whales feed by engulfing their own body mass in prey-laden water for subsequent filtration of prey via rows of baleen on the upper jaw. This is the largest biomechanical action in the world, but what does it costs whales to perform such a lunge? Simone and colleagues answer that question in a new Science Advances paper https://www.science.org/doi/10.1126/sciadv.ade3889
where we measured energy expenditure as a function of lunge rate.

We show that lunge feeding is energetically cheap for humpback whales: a 30 ton humpback whale only requires 225g of prey in 21m^3 of engulfed water to pay for a feeding lunge. This means that humpback whales can be much more flexible in the quality of prey patches they target than previously thought.
Thus, the biggest biomechanical action on the planet is spectacular, but cheap.

We also estimate the field metabolic rate of these megapredators from their breathing rates showing that humpback whales are not nearly as expensive as previously suggested: an adult 30 ton humpback whale needs about 200 tons of fish and krill per year to meet its energy requirements.

23/06/2023

Big congrats to Sylvester on his MSc degree on harbour seal lek-behaviour!:)

22/06/2023

Ever wondered how we can reduce underwater noise from shipping to reduce impacts on marine mammals? Then check out our new paper in Science Advances: https://www.science.org/doi/10.1126/sciadv.adf2987
Global reductions in shipping noise are needed to reduce impacts on marine wildlife. In this study we show that the noise impact of large cargo vessels can be reduced by sailing a bit slower: a 20 % speed reduction means that 75% less animals will be negatively affected by noise, and in marine protected areas, a 50% speed reduction will reduce the noise impact by 98%.
We conclude that slowdowns in combination with other noise reduction measures such as technological modifications and rerouting of shipping lanes are readily available, effective, and scalable tools to reduce the effects of the dominant human noise source in the world’s oceans.
This was a fantastic collaboration between Charlotte R. Findlay, Laia Rojano-Doñate, Jakob Tougaard, Mark Johnson, and Peter Teglberg Madsen. With huge thanks to generous support from the EU Horizon 2020 SATURN project (www.saturnh2020.eu).

22/05/2023

Please enjoy Lauras new paper in Elife: https://elifesciences.org/articles/84190
We use bat-borne tags and DNA metabarcoding of f***s to test the hypothesis that greater mouse-eared bats make immediate foraging decisions based on prey profitability and changes in the environment. We show that these bats use two foraging strategies with similar average nightly captures of 25 small, aerial insects and 29 large, ground-dwelling insects per bat, but with much higher capture success in the air (76%) vs ground (30%). However, owing to the 3–20 times larger ground prey, 85% of the nightly food acquisition comes from ground prey despite the 2.5 times higher failure rates. We find that most bats use the same foraging strategy on a given night suggesting that bats adapt their hunting behavior to weather and ground conditions. We conclude that these bats use high risk-high gain gleaning of ground prey as a primary foraging tactic, but switch to aerial hunting when environmental changes reduce the profitability of ground prey, showing that prey switching matched to environmental dynamics plays a key role in covering the energy intake even in specialized predators.

24/04/2023

Vessels are by far the dominant sources of anthropogenic noise at sea, but how often are marine mammals exposed to vessel noise? As part of the EU funded SATURN project we sought to answer that question with sound recording dtags on harbour seals in the North Sea. In the resulting paper lead by our colleague Dominik Nacthsheim in Scientific Reports, we show that seals on average are exposed to four louder vessels per day despite that most of the seals where spending time with marine protected areas. Importantly, less than 1/3 of the noise exposures could be explained by AIS data, highlighting that noise exposure modelling from such data is highly unreliable at least in the North Sea.
Read the paper here: https://marinebioacoustics.wordpress.com/publications/

25/03/2023

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

03/03/2023

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.

21/02/2023

Interesting job with our colleagues in Roskilde:

Vacancy at Department of Ecoscience - Marine Mammal Research, Aarhus University