Perspectives of conservation of pond-breeding frogs (focusing on the Nagoya Daruma pond frog) in rice paddy areas in Japan

Abstract

It has been two decades since the crisis of amphibians gathered attentions and triggered the intensifications of research on the reasons of declines and ecology of amphibians. The reasons for declines differ place to place and species to species but the main threats are the loss of wetland, habitat fragmentation and environmental pollution. In Japan, since the large part of natural wetlands has been lost, rice paddies and related areas have played important roles as substitute habitat for wetland species and supported rich indigenous ecosystems. The modernization of agriculture and increase of abandonment of farming however drastically changed these environments. Anuran species, especially pond-breeding frogs, are very common and representative of rice paddy ecosystems. Most of frogs are sensitive to environmental pollution and require both aquatic and terrestrial habitats to complete life cycle, they are considered bio-indicator of environmental changes of rice paddy area. For this paper, I focused on an endangered pond-breeding frog, the Nagoya Daruma pond frog (Anura: Ranidae, Pelophylax porosa brevipoda Ito, 1941), because its life history is closely linked to rice paddy areas. Because most of its natural habitat has been lost, and currently no population in natural habitat is known, for the conservation of the frog, it is vital to study the ecology in the areas. The main threats for the species are changes in yearly water management in rice paddies, improvements of drainage by agricultural modernization and hybridization between Pelophylax porosa nigromaculata. In this paper, I reviewed the situations of amphibians, the relationship between rice paddy area and frogs, conservation of frogs in agroecosystem and life history and ecology of P. p. brevipoda for discussing conservation of frogs in rice paddy area especially P. p. brevipoda.