Chirp rate is independent of male condition in a synchronising bushcricket

• Published in: Journal of insect physiology 2006-03, Vol.52 (3), p.221-230
• Main Authors: Hartbauer, M., Kratzer, S., Römer, H.
• Format: Article
• Language: English
• Subjects: age; Age Factors; Animals; body condition; Body Weight - physiology; Bushcricket; Call rate; calling behavior; calling costs; Calling energetics; Costs; Diet; energy cost of activities; energy metabolism; experimental diets; Gryllidae - physiology; insect communication; Male; male age; male songs; males; mating behavior; Mecopoda elongata; nutritional status; Respirometry; Sexual Behavior, Animal - physiology; Statistics, Nonparametric; stridulation; temporal variation; Tettigoniidae; Vocalization, Animal - physiology
• ISSN: 0022-1910; 1879-1611
• DOI: 10.1016/j.jinsphys.2005.10.006

Males of the bushcricket Mecopoda elongata synchronise their chirps with neighbouring males, but because synchrony is imperfect, one male's chirp preceeds the other by some 50–200 ms. Since a male's intrinsic chirp rate is critical for the establishment of the leader role in a duet, and females prefer the leader in a choice situation, we investigated a possible condition dependence of this male trait. In a duet leader males are usually those calling at a higher intrinsic rate; therefore, we investigated whether calling at a higher rate indicates male condition. The calling metabolism was quantified in a respirometer; the factorial slope of males calling at a high rate was three times higher compared to males calling at lower rates. Males produce on average 3.4 singing bouts/per night, and there is a significant increase in chirp periods (CPs) with successive singing bouts. Call properties were investigated throughout a male's life; chirp period increases significantly with age. Two groups of males were reared on either a low- or a high-nutrition diet, and the influence of male condition on different song parameters was investigated. CPs in two feeding regimes did not differ significantly, although males of the low-nutrition diet group were significantly affected by nutrition with respect to mortality, a delayed last moult and reduced weight as adults. We therefore conclude that solo chirp rates do not reflect phenotypic male condition properly.