STUDIES ON THE BEHAVIOR OF TRIMERESURUS FLAVOVIRIDIS (HALLOWELL, 1860), A VENOMOUS SNAKE, ON AMAMI OSHIMA ISLAND IN REGARD TO SPEED OF MOVEMENT, NOCTURNAL ACTIVITY AND SENSITIVITY TO INFRA-RED RADIATION

The actions of Trimeresurus flavoviridis in a dark, isolated place were wandering and resting. In this state, the momentary speed was measured from the time required for a part of the snake s body to pass through a distance of 30 cm. The average speed was 114.8 cm/ minute at 20°C indifferent to the intensities of illumination from 2 to 2300 luxes. The prowling speed was measured from the time required for a snake to pass erratically through a distance of 136 cm. Average speeds were 60.4, 68.0 and 169.5 cm/ minute under 2, 100 and 2,000 luxes. The duration of the striking pose seemed to be prolonged when the snake was active and wild. The daily activity of the snakes was quantitatively observed in a snake pit in Ap1il, August and September. From sunset to sunrise they wandered about actively on the ground, climbed trees and swam in the water, and the peak of the activity was between 1 and 4 AM. Correlation of the activity of the snakes with meteorological factors was tested and shown to exist between values of logarithmic intensity of illumination, solar radiation, temperature and humidity with the coefficients, -0.741, -0.532, -0.492 and +0.486. The activity of the snakes was suppressed by artificial lighting at night during a few hours, and rainfall evoked the transient emergence of the snakes in the darkness but the effect of rainfall was inferior to that of light. The blindfolded snakes responded sensitively to the radiation. The first reaction was tongue flicking, and the head followed the movement of a radiant body. The threshold of the sensible radiation was measured. In blindfolded snakes, the end point of the sensible radiation from a small electric heater was 0.34-3.37×10-4 cal/cm2/sec with an average of 1.22×10-4 cal/ cm2/sec among 9 snakes. Snakes with dosed pits were insensitive to the energy of 11.9-21.7×10-4 cal/ cm2/sec. After the plugs were removed, the sensitivity returned to the initial state. The threshold was approximately one tenth smaller when a hand and a rat were used as the heat sources. The sensitivity was not changed when one of the facial pits was plugged. The orientation with a single pit was still accurate to direct a strike