Limnonectes Research Articles

Breeding Behavior and Nest Construction in a Vietnam Frog Related to Rana blythi

One of the most interesting groups of Southeast Asian ranids are the fanged frogs, Rana blythi, R. kuhlii, and their relatives (Emerson and Berrigan, 1993). Although the natural history is imperfectly known for only about half of the species, the group already encompasses almost as much variation in reproductive biology as seen across all other frogs (Emerson, 1994; Iskandar, unpubl.). In addition to their odd reproductive behaviors, these frogs are characterized by an unusual complex of sexually dimorphic features, including enlarged heads and fangs in males (Inger, 1966; Emerson, 1994). Males of most species are also larger than the females. These features suggest the possibility of male-male combat, as is the case in other ranids with large males (Shine, 1979), but it has never been reported. Below I provide new information regarding the breeding biology of one of the fanged frogs, Rana cf. blythi, including the first report of aggressive encounters between males. This frog is a member of a group of common, widely distributed forest species occurring from Burma through Borneo and Java. These species oviposit in shallow nests excavated in gravel and sand bars of forest streams (Inger, 1966; Dring, 1979). Recently, Emerson (1992) reported on some aspects of courtship and nest building in a Bornean population. My additional observations are significant because they are on a different population of the species group and because of the general lack of information on the natural history of Asian frogs. During fieldwork in Vietnam, I observed eight nests of Rana cf. blythi on two forest streams separated by 20 km. Five nests were found 6-7 April 1995, at Buoenloy Village, Ankhe District, Gia-Lai Province, southern Vietnam (20 km NW of Kannack, 14'20'N 108036'E) along a permanent stream flowing through a rain forest. The stream was about 5 km long and 4 m wide and was under forest canopy for most of its length. The banks were steep, and the bottom was a mixture of rocks and coarse-grained sand. Maximum depth of the stream was 10-20 cm near the end of the dry season (April) and > 50 cm during the rainy season. The nests were constructed in quiet, straight reaches of the stream, where the bottom was coarsegrained sand and a 1-3 cm layer of dead leaves formed near the bank. Similar nest sites have