2001 Volume 65 Issue 5 Pages 517-522
The population of Rana porosa brevipoda has recently been decreasing and the species has been disappearing from previously observed habitats. Following this, R. porosa brevipoda was acknowledged as a threatened species in the Red Data Book. For the purpose of understanding the states of distribution and habitat conditions of R. porosa brevipoda, a survey of individual frog numbers was conducted in paddy fields in the Ina Basin, Nagano Prefecture, Central Japan. A concurrent survey of the closely related R. nigromaculata and of intermediate hybrids of the two species was conducted to clarify interspecific relations. An interview survey regarding cultivation methods and consolidation of paddy fields was conducted amongst farmers and administrative officials to provide information on the conditions of frog habitats. Habitats of R. porosa brevipoda were confirmed in Tatsuno Machi, Minowa Machi, Minamiminowa Village, Ina City, Komagane City and Takamori Machi. Existence of R. porosa brevipoda in areas abutting previously observed habitats varied according to dividing of the areas by roadway, structures and rivers. As a result of analysis using quantification theory type II, the primary factor involved in decreased individual densities of R. porosa brevipoda appeared to be paddy field consolidation.
