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Herring gulls feeding on a recent invader in the Wadden Sea, Ensis directus

By
Gerhard C. Cadée
Gerhard C. Cadée
Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, The Netherlands (e-mail: Cadee@nioz.nl)
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Published:
January 01, 2000

Abstract

The American razor clam Ensis directus has been a successful non-indigenous invader in the Wadden Sea since the late 1970s. It often shows poorly understood mass mortalities in the winter half-year, which are also known from its native area. During such mass mortalities Ensis directus partly leaves its burrow and, as it is unable to re-burrow, is an easy prey for herring gulls during low tide. During a mass mortality in March 1999, Ensis consumption by herring gulls was studied. Shell fragmentation was achieved by shaking the shell vigorously, not by hammering. This caused characteristic shell fragmentation ranging from small fragments broken from one or both valves near the middle, to both valves broken near the middle, but still connected by the ligament. About one-quarter of the shells remained undamaged. No other predators are known to produce similar Ensis shell fragments. In taphonomic studies the importance of predators in fragmenting shells should be taken into account.

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Contents

Geological Society, London, Special Publications

The Evolutionary Biology of the Bivalvia

E. M. Harper
E. M. Harper
Cambridge University, UK
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J. D. Taylor
J. D. Taylor
The Natural History Museum, UK
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J. A. Crame
J. A. Crame
British Antarctic Survey, UK
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Geological Society of London
Volume
177
ISBN electronic:
9781862394254
Publication date:
January 01, 2000

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