Ecological Traits of a Common Japanese Pit Viper, the Mamushi (Gloydius blomhoffii), in Kyoto, with a Brief Geographic Comparison

Abstract: Gloydius blomhoffii is a common pitviper distributed throughout Japan except for Okinawa Prefecture. To understand intraspecific geographic variation of this widely distributed snake, I describe several of its basic ecological traits observed during a 31-year-field survey conducted in the forest of Ashiu, northeastern Kyoto, in the western region of the mainland of Japan, and compare these traits with those reported in previous studies conducted in widespread areas of Japan. Body length of G. blomhoffii in Kyoto was smaller than that in the northernmost range and larger than that in the southernmost range. Sexual size dimorphism in snout-vent length, tail length, and body mass showed the same trends as in other areas. The sex ratio of the collected snakes was biased to females, which has not been observed in other studies. Pregnant females showed higher body temperature than males and non-pregnant females at a given air temperature. Parturition period, litter size, and body size of neonates generally overlapped with those reported in previous studies. Stomach contents were found only in 9.1% of snakes and consisted of rodents, frogs, and newts, which are prey items already known in G. blomhoffii. Although the forest in Ashiu has been incurred drastic environmental degradation, no obvious change in body size was detected over the study period. This study adds information on ecological traits of G. blomhoffii based on a population-level study and will facilitate future intensive field research to understand this common, but still poorly investigated, venomous snake endemic to Japan.