The importance of the facial pit of the Northern Pacific rattlesnake (Crotalus viridis oreganus) under natural conditions in southern British Columbia

The facial pits characterizing the snake subfamily Crotalinae have been demonstrated to be important as thermoreceptors in detecting the presence of prey animals and in directing the stroke towards them. So specialized a receptor as the pit organ, if it is to survive, must be functionally effective. If this organ is important in locating prey under natural conditions it would be expected that if these pits were destroyed this importance would be reflected in growth rates, weight changes,, or survival. In twenty of forty snakes collected in the spring of 1963 the pits were destroyed by electric cautery. After weighing, measuring, and marking, the snakes were released at the point of capture. The growth of the recaptured cauterized and non-cauterized snakes was compared. In addition, controlled tests were made with the recaptured snakes, using live mice and light-proof boxes to determine the effectiveness of cautery. A significant statistical difference was found in the growth rates of the females, the cauterized snakes growing more slowly. No difference was found in the growth rates of the males. However, the controlled tests indicates the pits to be important to the males as well as to the females. Weight changes were too variable to reveal differences between normal and cauterized snakes and no difference in survival was evident between the two treatments. To overcome the effect of individual variation in growth rate further study is required of larger samples over a longer time period.Science, Faculty ofZoology, Department ofGraduat