Pry. Backwell et al., PILLAR BUILDING IN THE FIDDLER-CRAB UCA BEEBEI - EVIDENCE FOR A CONDITION DEPENDENT ORNAMENT, Behavioral ecology and sociobiology, 36(3), 1995, pp. 185-192
In the fiddler crab (Uca beebei) males build a small mud pillar next t
o their burrow which increases their attractiveness to females. Three
hypotheses were tested to explain inter-male variation in pillar-build
ing. (1) The benefits of pillar-building are density dependent. The ex
perimental addition of vertical structures did not support this hypoth
esis as there was no change in the level of pillar-building. (2) There
are two classes of males (pillar-builders and non-pillar-builders). T
his could either be due to an alternative mating strategy, or because
pillar building is age or size-dependent. There was also no support fo
r this hypothesis. (3) Pillar-building is an honest signal of male qua
lity dependent on body condition. A food supplementation experiment wa
s performed. Addition of food affected several aspects of male behavio
ur and resulted in a two fold increase in the number of pillars built
between control and food treatments (P < 0.001). However, the percenta
ge of males building pillars did not increase significantly. Pillar bu
ilding in this species has been attributed to sensory exploitation. Ou
r results indicate that a trait which may well have evolved through se
nsory exploitation also appears to be condition-dependent. We emphasis
e that showing that an ornament or behaviour is condition-dependent do
es not necessarily mean that it evolved through ''good gene'' processe
s. However, in terms of its current selective value, pillar building m
ay be maintained through female choice because it acts as a signal of
male condition.