Vol. 50 No. 3, 2011

Is Ovophis okinavensis Active Only in the Cool Season? Temporal Foraging Pattern of a Subtropical Pit Viper in Okinawa, Japan

Yohei Kadota

Department of Zoology, Graduate School of Science, Kyoto Univ., Sakyo-ku, Kyoto 606-8502, Japan

Yohei Kadota (2011) Snakes are usually active in the warm season rather than the cool season because they are ectothermic animals that rely on external heat sources to maintain their body temperatures. However, previous studies on Ovophis okinavensis showed that this snake is most active in winter to early spring, presumably to exploit actively breeding frogs. This unusual activity pattern of O. okinavensis may simply reflect the fact that the availability of prey animals is restricted to this season, which obliges the snake to engage in feeding activities during periods of low temperatures. To test this hypothesis, I examined seasonal activity patterns of both O. okinavensis and frogs in the study area, where several species of frogs aggregate for breeding from winter to summer. Emergence sites of snakes well corresponded to those of frogs. Snakes and frogs were frequently found in both the warm and cold seasons. The daily emergence number of snakes was strongly correlated with that of frogs. These results suggest that O. okinavensis exhibits a foraging strategy that is adjusted to spatial and temporal fluctuations of the emergence of frogs.

Key words: Seasonal activity, Snake, Viperinae, Ryukyu Archipelago, Frogs.

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