Adult frogs of the Rana nigromaculata group were collected at eleven localities in Iwate Prefecture, and the mid-dorsal line, dorsal black spots, and hindlimb length were compared among populations. The characteristics of Rana brevipoda porosa were seen in the populations from the paddy fields along the River Kitakami from the southern to the central part of Iwate Prefecture. Frogs with the characteristics of Rana nigromaculata were predominant in the populations from the northern part of this prefecture. Frogs of the Rana nigromaculata group were not found in the eastern part of Iwate Prefecture.
In the early spring of 1984, there was much snow and the air temperature was unusually low. In Donchi-ike pond, the egg laying of toads began on April 17, which was 9 days later than in 1983. In the first half of the breeding period, the emergence of female toads was interrupted by falling temperatures, and the breeding period was extended.