Author(s): Keiji Watabe; Atsushi Mori; Noriyuki Koizumi; Takeshi Takemura
Linked Author(s): Takeshi Takemura
Keywords: Rana porosa porosa; Tokyo Daruma Pond Frog; Climbing capability; Ecosystem conservation; Japan
Abstract: Frogs often drown in agricultural canals with deep concrete walls that are installed commonly in paddy areas in Japan because they cannot escape after falling into the canal. To enable frogs to escape from the canals, we investigated the preferable angle of sloped walls, water depth and flow velocity as a partly escape countermeasure for Rana porosa porosa. Walls with slopes of 30-45 degrees allowed 50-60% of frogs to escape from experimental canals, the frogs especially easily climbed the 30 degree sloped walls. Approximately 80% of the frogs reached the sloped walls when the canal was so deep or fast that the frogs could not stand on the bottom. The frogs could neither swim long-distances nor remain a long-time under running water. Therefore, walls sloped less than 30 degrees and control of both water depth and flow velocity appears important for enabling frogs to easily escape from the canals.