Seasonal Changes in Movement Patterns and Body Exposure Frequencies of Mamushis (Gloydius blomhoffii) and Their Diurnal Activity in a Mountainous Habitat of Northeastern Kyoto, Japan

Abstract

Mamushis (Gloydius blomhoffii) are widespread and common venomous snakes in Japan. Generally, G. blomhoffii are considered a nocturnal species, but some literature suggests that these snakes may be active also during daytime. We conducted radiotelemetric surveys in a mountainous forest in Kyoto to clarify the seasonal and diurnal activities of G. blomhoffii. We defined snake body exposure (visible or hiding) as an index of snake activity. We recorded a total of 295 fixes (187 during daytime and 108 at night) for nine snakes from 2020 to 2021. Time of day did not affect snake body exposure. Environment, season, and air temperature influenced body exposure tendency. Monitored snakes were usually visible when in forest habitats, whereas they were frequently hiding under shelters in riverside habitats. Mean home range size of G. blomhoffii was 1.03 ha and was relatively small compared to other snake species. Mean daily displacement was higher in August and September and lower in other months. We conclude that G. blomhoffii are a cathemeral species, active both during daytime and at night, and vary their activity and movement depending on season, temperature, and environment. The different tendencies of body exposure between forest and riverside habitats likely reflect a strategy to avoid predators and/or overheating. Unlike previous visual-based anecdotal information, use of radiotelemetry enabled us to reveal the true activity patterns of G. blomhoffii without biases related to searching ability.