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Visual ecology of the fiddler crab, Uca tangeri: Effects of sex,viewer and background on conspicuousness
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Orientador(es)
Resumo(s)
We investigated the visual ecology of the coloration of the eastern Atlantic fiddler crab, Uca tangeri, with
particular attention to predator (e.g. avian) and conspecific vision. Spectral reflectance measurements were
made on different body parts used in possible intraspecific communication as well as background habitats
including crab-made materials (e.g. mudballs). Avian-based and crab-based visual models were used to obtain
different estimates of crab conspicuousness to potential predators and conspecifics. We found that
male body parts (except for dorsal carapace) were significantly more conspicuous to conspecific viewers
than female equivalent body parts, and showed greater within-body contrast estimates. Moreover, male
major claw areas differed in reflectance properties, producing variation in conspicuousness that fit signalling
predictions: areas visible during claw-waving events were most conspicuous against the background
sky, whereas areas visible in nonwaving positions were more conspicuous against substrate backgrounds.
For avian vision, sexually dimorphic coloration results in males being generally more conspicuous than
females (in terms of brightness contrast) against all backgrounds, however, there was no sexual dimorphic
conspicuousness of carapace coloration. Furthermore, one of the most conspicuous features of both male
and female crabs is an area that is likely to be more visible to crabs (mouthparts) than to avian predators
from above. While conspicuousness varies with background, the most conspicuous background for male
signalling parts (major claw) is dark mudballs, suggesting that males may increase the conspicuousness
of their signals by modifying their signalling environment.
Descrição
Palavras-chave
Avian vision Coloration Conspicuousness Fiddler crab Visual ecology Uca tangeri
Contexto Educativo
Citação
Animal Behaviour, 2008, 75, 175-188