Female choice of large males in the treefrog Hyla ebraccata

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Abstract

The mating behaviour and male mating success of Hyla ebraccata were examined over three study periods. Mated males were larger than unmated males on a significant number of nights and for one of the three study periods. In field observations of pair formation, female behaviour was consistent with choice of large males: females moved freely through the chorus, remaining within 10 cm of males larger than the nightly mean, before the male initiated amplexus. In 27% (n = 3) of these observations, males chased and fought over the female. However, the females removed two of these three males from amplexus, suggesting that females can also exercise choice after amplexus. There was a significant negative correlation between male size and dominant frequency of the primary note, indicating that the male's advertisement call contained size-related information. Comparisons of the size of mated and unmated males suggest that two factors may have affected the degree to which female choice influenced male mating success. First, the distance between calling males may have limited the opportunity for females to express a mating preference. Secondly, an increase in mean and a decrease in the variance of male size in one of the three study periods also may have limited the ability of females to express a preference for large males.

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