Reproductive characteristics of Elaphe quadrivirgata (Serpentes: Colubridae) from ecologically dissimilar main island and island populations

Abstract

We compared reproductive characteristics of a snake (Elaphe quadrivirgata) from two geographically distinct populations, which differ considerably in habitat use and diet. Snakes in Shiga Prefecture, in the central western area of the main island of Japan, occupy open rice fields and predominantly eat frogs. Snakes on Yakushima Island, in southwestern Japan, occupy a forest environment and mainly eat lizards. Maternal body size of snakes from Yakushima was significantly smaller than that of snakes from Shiga. Oviposition date was significantly later in snakes from Yakushima than in those from Shiga, and the former laid a smaller number of considerably elongated eggs than the latter. Relative clutch mass was significantly higher in the Shiga than in the Yakushima population, but egg mass in relation to maternal body mass of the latter was larger than that of the former. Hatchlings of Yakushima were larger than those of Shiga. This size difference in hatchlings was not fully explained by differences in egg size. These differences in reproductive characteristics between the two populations do not seem to be a consequence of morphological constraints of dam snakes. Instead, we presume that the differences in reproductive characteristics reflect local adaptations.

Keywords:

• allometry
• clutch size
• egg size
• geographic variation
• life history

Acknowledgements

We are grateful to P.T. Gregory for invaluable comments on the manuscript and N.B. Ford and S.E. Vincent for comments on early version of the manuscript. We thank K. Mochida for providing a map and T. Iwasaki, N. Narumi, E. Nagata and many colleagues of the Laboratory of Ethology, Kyoto University, for field assistance and maintenance of captive animals. We also thank many inhabitants and researchers for their hospitality during our stay at the Kyoto University Yakushima Field Station. The Wildlife Research Center of Kyoto University permitted us to stay at Yakushima Field Station. Animals were handled according to the Guideline for Animal Experiments of Kyoto University. This work was partially supported by the Sasagawa Scientific Research Grant from the Japan Science Society (15–247) to KT, and by Grants for Biodiversity Research from the 21st Century COE (A14) and the Global COE (A06) Programs of Kyoto University.