Body Temperature of Subtropical Snakes at Night: How Cold is Their Blood?

Abstract

Thermal biology of snakes has been extensively studied, but vast majority of them deals with diurnal species distributed in temperate regions. During a long-term field study of a pitviper on subtropical Okinawa Island, the Ryukyu Archipelago, Japan, we had an opportunity to obtain body temperature data from six syntopic species of snakes belonging to the families Colubridae, Xenodermidae, Viperidae, and Elapidae that are active at night there. Mean body temperature of those nocturnally active snakes over a year was relatively low, ranging from 17.7 to 22.3°C, although research effort was largely biased to the cooler period of the year. Lowest body temperature of the six species ranged from 10.9 to 20.0°C. Irrespective of species, body temperature was highly correlated with both ambient air and substrate temperatures. Importance of future research on the activity of subtropical, nocturnal snakes under low temperature is briefly discussed.