TiHo researchers investigate the hearing of the marine mammals.
Researchers from the Institute for Terrestrial and Aquatic Wildlife Research of the University of Veterinary Medicine Hannover Foundation (TiHo) are investigating the hearing of gray seals (Halichoerus grypus) under the leadership of Professor Dr. Ursula Siebert and Dr. Andreas Ruser.
They published the first results in the online specialist magazine Plos one (www.plosone.org). The investigations were financed by the German Federal Agency for Nature Conservation (BfN) in order to increase knowledge about the effects of underwater noise on marine mammals. They are part of a multi-year, extensive BfN research program. The measuring system was supported by Technical Center Army Office 71 of the German Armed Forces.
“We urgently need to learn more about how well and in which frequency range gray seals hear,” says Professor Dr. Ursula Siebert, Head of the institute. “The last scientific publication on this topic dates back to 1975.”
Noise pollution in the sea is continuously increasing: shipping traffic, construction works in the sea, blasting, sound cannons to search for crude oil or the use of sonar devices stress the animals. The scientists need precise data about the hearing of gray seals in order to assess the effects of underwater noise on the animals. This seal species, along with porpoises and seals, is among the most common marine mammals in the North and Baltic Seas.
For their current study, the researchers investigated six gray seals from rearing stations. Dr. Andreas Ruser explains: “Basically, we proceeded according to the principle which we know from ear specialists.”
In contrast to humans, however, animals cannot say when they hear a tone, so the challenge for the researchers was to find out whether the seals perceive a tone or not. The researchers sedated the gray seals shortly before they were to be released into the wild. Then they played tones to them and measured the nerve impulses transmitted from the cochlea to the auditory nerve. As soon as the animals woke up again, the researchers were able to release them into the wild.
Since seals close their external ear channel when sedated, it is impossible to treat them with ultrasound using speakers. “We therefore used specially adapted in-ear headphones,” explains Ruser. The researchers found out that gray seals, similar to humans, can hear in a frequency range between 1,000 and 20,000 hertz and are much more sensitive than previously known in a range higher than 3,000 hertz.
Furthermore, there are indications not yet confirmed that gray seals can also hear above 20,000 hertz. “Using this method, however, we can only prepare a so-called air audio diagram for wild animals, which means that measurements can only be carried out in the air. Sound waves are transmitted in a different manner under water. We therefore assume that gray seals hear even higher frequencies under water.”
Next, Ruser and his colleagues want to examine this difference with gray seals trained and held in human hands at the University of Southern Denmark, Odense: The gray seals must therefore “learn” to signalize whether they hear something, first above and then under water. The seals are thus to be trained to show a defined reaction as soon as they hear a tone. This training is carried out in the pool of the respective seal facility.
The tones are then played for the gray seals under controlled conditions using headphones or loudspeaker in the air and loudspeaker or hydrophones under water. “We are looking forward to the further results, particularly with regard to the hearing of the seals under water,” says Professor Siebert. “We are hoping for reliable evidence that shows to what extent seals are affected by the increasing noise pollution in the North and Baltic Seas.”
Gray seals are the biggest wild predators in Germany. They can live up to 35 years. With a length of 230 centimeters and an average weight of 220 kilograms, males are considerably larger than females, which can be up to 180 centimeters in length and may weigh 150 kilograms.
The employees of the Institute for Terrestrial and Aquatic Wildlife Research work in Hannover and at a branch of the TiHo in Büsum in Schleswig-Holstein. The focal points of aquatic wildlife research are basic research, applied research and monitoring. The aim is to investigate the biology and ecology of marine mammals and to assess the influence of humans on animals, their health and their population.
In-air evoked potential audiometry of grey seals (Halichoerus grypus) from the North and Baltic Seas
Andreas Ruser, Michael Dähne, Janne Sundermeyer, Klaus Lucke, Dorian S. Houser, James J. Finneran, Jörg Driver, Iwona Pawliczka, Tanja Rosenberger, Ursula Siebert
Plos one, DOI: 10.1371/journal.pone.0090824
For technical questions, please contact
Dr. Andreas Ruser
University of Veterinary Medicine Hannover Foundation
Institute for Terrestrial and Aquatic Wildlife Research
Phone: +49 511 953-8156
Sonja von Brethorst | idw - Informationsdienst Wissenschaft
Don't Give the Slightest Chance to Toxic Elements in Medicinal Products
23.03.2018 | Physikalisch-Technische Bundesanstalt (PTB)
North and South Cooperation to Combat Tuberculosis
22.03.2018 | Universität Zürich
Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
23.03.2018 | Event News
19.03.2018 | Event News
16.03.2018 | Event News
23.03.2018 | Materials Sciences
23.03.2018 | Agricultural and Forestry Science
23.03.2018 | Physics and Astronomy