Distribution of oviposition sites and environmental characteristics around these sites of Tokyo salamander, Hynob ius tokyoensis, at paddy fields of valley bottom in northeast region of Chiba Prefecture

Abstract

We surveyed the distribution of oviposition sites and environmental characteristics around these sites of Tokyo salamander (Hynobius tokyoensis) at paddy fields of valley bottom in northeast region of Chiba Prefecture in 2012. Fifty oviposition sites were detected from mid-March to late-April. The number of egg sacs found in each oviposition site ranged from 1 to 52 (9.4 egg sacs on average), and small-scale oviposition sites, which had less than 10 egg sacs, shared over 70% of the total number of oviposition sites. Generalized linear model (GLM) analysis based on six variables related to landing of adults and larva after metamorphosis (canal width, water depth, sediment depth, distance to forest on slope, canal bank slope, and area of oviposition site) , indicated that distance to forest on slope had a negative significant effect on their egg-sac number. Our results suggest the importance of spatial connectivity between oviposition sites and ordinary habitat for adults and larvae after metamorphosis (i.e. forest on slope) at micro spatial scale that allows the viability of Tokyo salamander population.