Nutritional effects on male calling behaviour in the variable field cricket

In the variable field cricket, Gryllus lineaticeps, females prefer higher c hirp rates and longer chirp durations in male calling song. Higher chirp ra tes are energetically more expensive to produce, but the energetic cost of calling does not vary with chirp duration. We tested the hypothesis that nu trition affects male chirp rate and chirp duration. Full-sibling brothers o f similar age were placed on high- and low-nutrition feeding regimes. There was no effect of feeding regime on male weight; neither group showed a sig nificant change in weight, and the two groups did not differ from each othe r in weight change. However, males on the high-nutrition feeding regime bot h called more frequently and called at higher chirp rates when they did cal l. The two groups did not differ in chirp duration, the duration of pulses within chirps or chirp dominant frequency. These results suggest that femal es select mates based on one nutrition-dependent call character (chirp rate ) and one nutrition-independent call character (chirp duration). In additio n, because males in the two groups did not show significant differences in weight change, and because males on the high-nutrition feeding regime engag ed in energetically more expensive calling, these results suggest that male s invest any excess energy above their basic maintenance requirements in th e production of call types that increase their attractiveness to females. T he absence of a relationship between body condition and calling song struct ure for males in the field may be a consequence of this pattern of energy a llocation. (C) 1999 The Association for the Study of Animal Behaviour.