Breeding Activity of a Stream-Breeding Toad, Bufo torrenticola

Abstract

The breeding activity of the stream-breeding toad (Bufo torrenticola) was studied in Mie Prefecture for three years from 1990 to 1992. Aggregation in the main pool, which was intensively investigated, occurred explosively in early April for 12-14 days. The oviposition period was 5-11 days in the main pool, and 14-17 days in the entire length of stream. First, many toads appeared on a particular section of the migration path, on their way to the stream. In about 300 individuals captured in the main pool, the males: female ratio was 2.0-2.4:1. The daily number of toads found in the main pool showed the normal distribution pattern with a sharp peak in the middle of the breeding period. Toads appeared to be most active during the nighttime. The onset of migration to the stream was affected by soil temperature rather than by air temperature; during the three years, maximum soil temperatures were 10.0-11.0°C, and minimum soil temperatures ranged 8.5-9.0°C. Oviposition activity in the main pool in 1991 and 1992 occurred in the later half of the breeding period, when the minimum water temperature was above 10.0°C. Breeding activity, however, was not strongly associated with weather conditions, probably because breeding is performed underwater.