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thought experiment: were some female dinosaurs ornamented?

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  • Stephan Pickering
    Rita Chan, Devi Stuart-Fox, T.S. Jessop, 2009. Why are females ornamented? A test of the courtship simulation and courtship rejection hypotheses. Behavioral
    Message 1 of 1 , Oct 31, 2009
      Rita Chan, Devi Stuart-Fox, T.S. Jessop, 2009. Why are females ornamented? A test of the courtship simulation and courtship rejection hypotheses. Behavioral Ecology IN PRESS. ABSTRACT. Female ornamentation was initially thought to reflect genetic correlation with the more elaborate male trait. However, this cannot explain female-specific ornamentation, such as the conspicuous coloration displayed by females of many species during breeding. Females may exhibit distinctive, reproductive coloration to 1) advertise receptivity and stimulate male courtship, or 2) advertise nonreceptivity when gravid to reduce male courtship, harassment, and potentially costly copulations. We tested both hypotheses in the Lake Eyre dragon lizard (Ctenophorus maculosus) by quantifying female coloration, using spectroradiometry and a model of lizard color perception, and male and female behavior across the female reproductive cycle. Females develop bright orange coloration on their throat and abdomen during the breeding season, whereas males remain cryptically colored. The onset of orange coloration was associated with enlarging follicles, acceptance of copulations, and escalation of male courtship. Rather than fading once females were no longer receptive, however, the intense orange coloration remained until oviposition. Furthermore, despite maximal coloration associated with nonreceptivity, males persisted with courtship and copulation attempts, and females increased rejection behaviors comprising lateral displays and flipping onto their backs (to prevent forced intromission), both of which emphasize the conspicuous ventrolateral coloration. These apparently costly rejection behaviors did not reduce male harassment, but did decrease the frequency of potentially costly copulations. These results suggest that 1) males do not determine female receptivity based on coloration alone, and 2) the potentially costly rejection behaviors may have evolved to reduce the direct costs of mating.
      STEPHAN PICKERING / Chofetz Chayim ben-Avraham
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