ECOLOGICAL NOTE ON THE GREEN FROGS DURING THE BREEDING SEASON, I

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  • 産卵期におけるモリアオガエルの生態について 第1報
  • 産卵期におけるモリアオガエルの生態について-1-
  • サンランキ ニ オケル モリアオガエル ノ セイタイ ニ ツイテ 1

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Abstract

The breeding season of the green frog (Rhacophorous schlegelii var. arborea OKADA et KAWANO) begins at the end of May and terminates at the begining of July in the Kanazawa district. In this season, the frogs are found on trees and under stones near ponds. The following observations were performed at four ponds which are situated on the campus of the Kanazawa University. The frogs were tagged with vinyl string of various colours or wire ring to facilitate the individual difference. Observation reveals (1) that the frogs did not migrate from pond to pond during the breeding season, (2) that each frog remained near the pond no longer than several hours each day, and then retired under stones or decayed woods, and (3) that the same male came out several times within 8 to 18 days after its first arrival. The shortest distance between the ponds is about 70 metres. The pattern of emergence of the frogs was observed mainly at the fourth pond. The number of frogs appearing during the breeding season showed three peaks, the first peak occurred from the 8th to the 10th of June, the second from the 13th to the 18th, the third from the 24th to the 27th of the same month. As shown in Fig. 3,this roughly corresponds to the meteorological conditions. In cloudy or rainy days some of the frogs were found throughout the daytime. When the weather was fine, the frogs were seen very rarely, while they come out abundantly in the cloudy or rainy day; on these days the humidity was very high (90-100%). The illumination intensity, therefore, seems to be related to this behaviour. This is also shown from the fact that the frogs were more abundant in the morning and the evening than in other times of the day even in the cloudy or rainy day. To reveal the fluctuation of the frogs which come into sight newly again during the season, the season was divided into five periods, each of 7 days, and the total number of frogs during each period were divided by the number of observations. The average obtained is shown in Fig. 5. The frequency of new individual appearance was higher in the second one fifth of the breeding season, but then it decreased as the season advanced. As stated above, the frogs remained for 8 to 18 days near the pond, but the population was found to decrease day by day in the later half of the season.

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