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Are Juvenile Grass Snakes, Natrix natrix, Aposematically Coloured?

Thomas Madsen
Oikos
Vol. 48, No. 3 (Mar., 1987), pp. 265-267
Published by: Wiley on behalf of Nordic Society Oikos
DOI: 10.2307/3565512
Stable URL: http://www.jstor.org/stable/3565512
Page Count: 3
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Are Juvenile Grass Snakes, Natrix natrix, Aposematically Coloured?
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Abstract

Most grass snakes have a yellow black bordered collar just behind the head. In neonates the contrast between the collar and the body colour is more distinct than in adults which makes the young snakes particularly conspicuous. Seventy-five normal (with a yellow collar) and 75 melanistic models of neonate grass snakes were manufactured from black plasticine and exposed in the study area. Ten experiments were carried out. The melanistic models were more subjected to avian predation than the normal models. I suggest that the yellow head collar could be a form of mimicry of aposematically coloured unpalatable insects. The lower bird predation on the normal models could thus be due to the birds interpreting these as being unpalatable.

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