Variation in mating pattern in a population of the Andean frog Hyla labialis

Unmated frogs and mated pairs from a population of individually marked Hyla labialis were captured, measured and released over four consecutive years in a highland valley of the Colombian Andes. Across eight prolonged breedin g seasons, three times more males than females were captured. On average, f emales were significantly larger than males. Although the largest reproduct ive males were larger than the smallest reproductive females, amplexing mal es were always smaller than the females they clasped. Larger males had no m ating advantage, because the body size distribution of males was the same f or mated and unmated males, and the average snout-vent length of mated male s was similar to that of unmated males. There was no indication of larger m ales taking over clasped females during male-male competition, because ther e was no size difference between males clasping gravid, spawning and spent females. Significantly size-assortative matings occurred on days when male availability per female was moderately high, but not when it was low, sugge sting that female mate choice is relatively more important than male-male c ompetition in shaping mating pattern.