Breeding behaviour of the Omei tree frog Rhacophorus omeimontis (Anura: Rachophoridae) in a subtropical montane region

Breeding behaviour of the Omei tree frog, Rhacophorus omeimontis, was studied during the egg-laying period (mid-April to late June) in south-west China. The operational sex ratio of the breeding population was male-biased at 3.0 +/- 0.8 (mean +/- SD) on a nightly basis in Pond A and 4.3 +/- 1.1 in Pond B. Pairs with a male clasping a female occurred in ponds first; the amplectant pairs moved to a neighbouring plant and then released foam in leaves 14-370 cm above the pond's water surface. Immediately, other males came to join the pair, forming an amplexing group of 2 to 7 males (for all 45 breeding units observed). Among the males no direct physical competition for possession of the females was observed. Females produced foam which surrounded the subsequently-laid eggs. The whole process of oviposition lasted 45-65 minutes. After ovipositing, males left the female, the female folded and lined neighbouring leaves with more foam produced to surround the eggs further. This process took 15-45 minutes. The numbers of eggs in a clutch ranged from 457 to 837 and eggs were between 2.9 and 3.4 mm in diameter; those two measures were negatively correlated with each other. Eggs hatched after 12-17 days; the larval period lasted 63-78 days. Fertilization success was positively related to the number of males participating in matings.