Temperature and velocity of water at breeding sites of Hynobius retardatus

The breeding sites of the salamander Hynobius retardatus were studied in the Tokachi district, Hokkaido, during the breeding seasons of 1985-89. Eighty-two breeding sites were divided into three types according to the velocity of water flow, i. e., high velocity areas (HVAs: more than 5cm/sec), low velocity areas (LVAs; 5cm/sec or less) and standing water areas (SWAs), and these occurred at the frequency of 13.4%, 52.4%, and 34.1%, respectively. In HVAs, the mean water temperature at the bottom did not differ from that measured just beneath the water surface. But in LVAs and SWAs, they differed significantly. Natural enemies (e. g., crayfish and larval caddis flies) were observed in 60.7%, 14.0%, and 0% of the total breeding sites in SWAs, LVAs, and HVAs, respectively. The mean water depth where egg sacs were attached was 3.1cm.