Meeting Abstract

25.9  Monday, Jan. 5  Unreliable signals of strength in male slender crayfish (Cherax dispar): costs of enlarged claws and the importance of resources during disputes WILSON, R S*; OLIVER, J; GOLDIZEN, A; BLOMBERG, S; Univ, of Queensland; Univ. of Queensland; Univ. of Queensland; Univ. of Queensland r.wilson@uq.edu.au

Unreliable signals of weapon strength are considered problematic for signalling theory and reliable signals are predicted to be the dominant form of signalling among conspecifics in nature. Previous studies have shown males of the Australian freshwater crayfish (Cherax dispar) routinely use unreliable signals of strength during simple experimental confrontations. We investigated the possibility that functional trade-offs associated with enlarged weaponry may be important in reducing any benefits for unreliable signaling. We found swimming speed was negatively correlated with chela size for males, but not females, suggesting a functional trade-off exists for males only. Decreases in swimming speed with increases in weapon size, suggest there could be important fitness costs associated with larger chelae. In addition, we examined whether unreliable signals of strength remain effective during confrontations in the presence of two different perceived resources (shelter and territory). Like previous studies of C. dispar, chela size was the most accurate predictor of the decision to engage in a fight and of eventual dominance. However, males whose chelae represented an unreliable signal of strength (i.e. poor strength for a given chela size), were less likely to decide to fight when in the presence of a shelter. Overall, territory ownership and the presence of shelter significantly decreased the probability of males deciding to fight; whereas these factors did not significantly affect the likelihood that males established dominance.