The variable colours of the fiddler crab Uca vomeris and their relation to background and predation
Date
2006
Authors
Hemmi, Jan
Marshall, Justin Nicholas
Pix, Waltraud
Vorobyev, Misha
Zeil, Jochen
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The Company of Biologists Ltd
Abstract
Colour changes in fiddler crabs have long been noted, but a functional interpretation is still lacking. Here we report that neighbouring populations of Uca vomeris in Australia exhibit different degrees of carapace colours, which range from dull mottled to brilliant blue and white. We determined the spectral characteristics of the mud substratum and of the carapace colours of U. vomeris and found that the mottled colours of crabs are cryptic against this background, while display colours provide strong colour contrast for both birds and crabs, but luminance contrast only for a crab visual system. We tested whether crab populations may become cryptic under the influence of bird predation by counting birds overflying or feeding on differently coloured colonies. Colonies with cryptically coloured crabs indeed experience a much higher level of bird presence, compared to colourful colonies. We show in addition that colourful crab individuals subjected to dummy bird predation do change their body colouration over a matter of days. The crabs thus appear to modify their social signalling system depending on their assessment of predation risk.
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Keywords
Keywords: animal; article; Australia; bird; Brachyura; ecosystem; female; male; physiology; pigmentation; predation; signal transduction; social behavior; Animals; Australia; Birds; Brachyura; Ecosystem; Female; Male; Pigmentation; Predatory Behavior; Signal Transd Body colour; Colour change; Fiddler crab; Predation
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Source
Journal of Experimental Biology
Type
Journal article
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2037-12-31
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