Friedrichskoog, Germany
Friedrichskoog, Germany

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Ruser A.,University of Veterinary Medicine Hannover | Dahne M.,University of Veterinary Medicine Hannover | Sundermeyer J.,University of Veterinary Medicine Hannover | Sundermeyer J.,Seal Center Friedrichskoog | And 7 more authors.
PLoS ONE | Year: 2014

In-air anthropogenic sound has the potential to affect grey seal (Halichoerus grypus) behaviour and interfere with acoustic communication. In this study, a new method was used to deliver acoustic signals to grey seals as part of an in-air hearing assessment. Using in-ear headphones with adapted ear inserts allowed for the measurement of auditory brainstem responses (ABR) on sedated grey seals exposed to 5-cycle (2-1-2) tone pips. Thresholds were measured at 10 frequencies between 1-20 kHz. Measurements were made using subcutaneous electrodes on wild seals from the Baltic and North Seas. Thresholds were determined by both visual and statistical approaches (single point F-test) and good agreement was obtained between the results using both methods. The mean auditory thresholds were ≤40 dB re 20 mPa peak equivalent sound pressure level (peSPL) between 4-20 kHz and showed similar patterns to in-air behavioural hearing tests of other phocid seals between 3 and 20 kHz. Below 3 kHz, a steep reduction in hearing sensitivity was observed, which differed from the rate of decline in sensitivity obtained in behavioural studies on other phocids. Differences in the rate of decline may reflect influence of the ear inserts on the ability to reliably transmit lower frequencies or interference from the structure of the distal end of the ear canal. © 2014 Ruser et al.


PubMed | University of Veterinary Medicine Hannover, Veterinary Clinic, SOS Dolphin Foundation Stichting SOS Dolfijn, Fjord and Baelt and 8 more.
Type: | Journal: Advances in experimental medicine and biology | Year: 2015

The project conducts application-oriented research on impacts of underwater noise on marine vertebrates in the North and Baltic Seas. In distinct subprojects, the hearing sensitivity of harbor porpoises and gray seals as well as the acoustic tolerance limit of harbor porpoises to impulsive noise from pile driving and stress reactions caused by anthropogenic noise is investigated. Animals are equipped with DTAGs capable of recording the actual surrounding noise field of free-swimming harbor porpoises and seals. Acoustic noise mapping including porpoise detectors in the Natura 2000 sites of the North and Baltic Seas will help to fully understand current noise impacts.


Ruser A.,University of Veterinary Medicine Hannover | Dahne M.,University of Veterinary Medicine Hannover | Dahne M.,German Museum | Van Neer A.,University of Veterinary Medicine Hannover | And 12 more authors.
Journal of the Acoustical Society of America | Year: 2016

Testing the hearing abilities of marine mammals under water is a challenging task. Sample sizes are usually low, thus limiting the ability to generalize findings of susceptibility towards noise influences. A method to measure harbor porpoise hearing thresholds in situ in outdoor conditions using auditory steady state responses of the brainstem was developed and tested. The method was used on 15 live-stranded animals from the North Sea during rehabilitation, shortly before release into the wild, and on 12 wild animals incidentally caught in pound nets in Denmark (inner Danish waters). Results indicated that although the variability between individuals is wide, the shape of the hearing curve is generally similar to previously published results from behavioral trials. Using 10-kHz frequency intervals between 10 and 160 kHz, best hearing was found between 120 and 130 kHz. Additional testing using one-third octave frequency intervals (from 16 to 160 kHz) allowed for a much faster hearing assessment, but eliminated the fine scale threshold characteristics. For further investigations, the method will be used to better understand the factors influencing sensitivity differences across individuals and to establish population-level parameters describing hearing abilities of harbor porpoises. © 2016 Acoustical Society of America.


Weirup L.,University of Veterinary Medicine Hannover | Muller S.,University of Veterinary Medicine Hannover | Ronnenberg K.,University of Veterinary Medicine Hannover | Rosenberger T.,Seal Center Friedrichskoog | And 3 more authors.
Marine Environmental Research | Year: 2013

Harbour seals as top predators and indicators for ecosystem health are exposed to increasing pressure caused by anthropogenic activities in their marine environment. After their lactation period of about 24 days pups are weaned and left to hunt on their own. Little is known about the development of their immune system and a better understanding of anthropogenic impacts on the general health and immune system of harbour seal pups is needed. mRNA transcription of six immuno-relevant biomarkers was analysed in 13 abandoned harbour seal pups from the North Sea, fostered at the Seal Centre Friedrichskoog, Germany. RNAlater blood samples were taken at admission, day 22 and before release and analysed using RT-qPCR. Significant differences in HSP70, cytokine IL-2 and xenobiotic biomarkers AHR, ARNT and PPARα transcription were found between admission, during rehabilitation and before release. Highest levels at admission may result from dehydration, handling, transport and contaminant exposure via lactation. The significant decrease is linked to health improvement, feeding and adaptation. The increase before release is suspected to be due to infection pressure and contaminant exposure from feeding on fish. Molecular biomarkers are a sensitive tool to evaluate health and pollutant exposure and useful to serve as early warning indicators, monitoring and case-by-case tool for marine mammals in human care and the wild. © 2013 Elsevier Ltd.


Lehnert K.,University of Veterinary Medicine Hannover | Lehnert K.,Helmholtz Center Geesthacht | Muller S.,University of Veterinary Medicine Hannover | Weirup L.,University of Veterinary Medicine Hannover | And 4 more authors.
Marine Pollution Bulletin | Year: 2014

Grey seals as top-predators bioaccumulate contaminants and can be considered as sentinels of eco-system health. Pups are weaned after a short nursing period, characterised by an enormous lipid transfer and exposure to contaminants. This study established molecular biomarkers of the xenobiotic metabolism and immune system to help assess health and immune status. mRNA transcription of AHR, ARNT, PPARα and cytokine IL-2 and heat-shock-protein HSP70 was measured in blood of grey seal pups and adults in rehabilitation and permanent care using RT-qPCR and compared to rehabilitating harbour seal pups and haematology values. In pups highest levels at admission in xenobiotic biomarker, HSP70 and cytokine transcription may show contaminant exposure via lactation, stress during abandonment and dehydration. The significant decrease may be linked to diet, health improvement and adaptation. Adults showed higher levels and more variation in biomarker transcription and clear species-specific differences between harbour and grey seal pups were found. © 2014 Elsevier Ltd.

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