Seals in motion : how movements drive population development of harbour seals and grey seals in the North Sea

The harbour seal Phoca vitulina and the grey seal Halichoerus grypus have been inhabitants of the Wadden Sea since millennia. Prehistoric findings indicate the presence of both species around 5000 BC. This changed dramatically in the mid Middle-Ages as around 1500 AC, the grey seal disappeared from...

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Bibliographic Details
Main Author: Brasseur, Sophie Marie Jacqueline Michelle
Other Authors: Reijnders, P.J.H., Aarts, G.M.
Format: Doctoral or Postdoctoral Thesis
Language:English
Published: Wageningen University 2017
Subjects:
animal ecology
halichoerus grypus
netherlands
phoca vitulina
pinnipedia
population biology
seals
wadden sea
dierecologie
nederland
populatiebiologie
waddenzee
zeehonden
harbour seal
Phoca vitulina
Online Access:https://research.wur.nl/en/publications/seals-in-motion-how-movements-drive-population-development-of-har
https://doi.org/10.18174/418009
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Summary:The harbour seal Phoca vitulina and the grey seal Halichoerus grypus have been inhabitants of the Wadden Sea since millennia. Prehistoric findings indicate the presence of both species around 5000 BC. This changed dramatically in the mid Middle-Ages as around 1500 AC, the grey seal disappeared from the Wadden Sea as a consequence of persecution. With growing hunting pressure, especially in the 20th century and concurrent habitat destruction and pollution, the harbour seals reached all time low numbers in the 1970’s. Banning the hunt in countries around the southern North Sea, limiting pollution and protection from disturbance allowed the harbour seals to slowly recover and the grey seals to return to the Wadden Sea. In this thesis the population trends and inherent dynamics of the recovery for both species is described. Also the movements of individual animals are studied to explain possible mechanisms.

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