MALE MATING SUCCESS, CALLING AND SEARCHING BEHAVIOR AT HIGH AND LOW-DENSITIES IN THE FIELD CRICKET, GRYLLUS-INTEGER

Mating behaviour of male field crickets, Gryllus integer, was studied during 10-h observation periods at night and early morning in a large outdoor enclosure placed in the natural habitat. Duration of nightly calling, amount of searching, and mating frequency were determined over 113 nights for 93 and 111 males at high and low density, respectively. Male body weight was also determined. Males called significantly more and searched less at low density. In the low-density population, body weight and calling duration were positively correlated, whereas searching was inversely correlated with both calling and body weight. Mating frequency was positively correlated with calling duration and inversely correlated with searching at low density. Mating frequency did not vary with body weight at either density. There were no significant correlations at high density. Directional selection was estimated using covariance analysis as the total selection (s') on calling, searching, and weight (including selection on correlated traits). Partial regression coefficients (β′) were used to estimate selection directly on each trait alone. Total selection favoured calling and opposed searching at low density. There was no selection on body weight at low density and there was no selection on any of the observed traits at high density. Data are discussed in terms of density-dependent fluctuations in male mating success and maintenance of phenotypic and genetic variation. © 1992 The Association for the Study of Animal Behaviour.