Chirp rate is independent of male condition in a synchronising bushcricket.
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.
Hartbauer
M
M
Department of Zoology, Karl-Franzens University, A 8010 Graz, Universitätsplatz 2, Austria. manfred.hartbauer@uni-graz.at
Kratzer
S
S
Römer
H
H
D000367:Age Factors; D000818:Animals; D001835:Body Weight / Q000502:physiology; D004032:Diet; D006135:Gryllidae / Q000502:physiology*; D008297:Male; D012726:Sexual Behavior, Animal / Q000502:physiology; D018709:Statistics, Nonparametric; D014828:Vocalization, Animal / Q000502:physiology*