Seasonal and daily activity patterns in a Canadian population of the prairie rattlesnake, <i>Crotalus viridus viridis</i>

Abstract

The seasonal and daily activity patterns of a Saskatchewan population of Crotalus viridus viridis is presented. Snakes emerged from hibernation in late April and migrated into the surrounding river valley and upland regions in early May. Adult migration preceded that of immature age-classes. Several gravid females occupied a rookery near the hibernaculum during the summer months and remained there until parturition. Females did not occupy this site in successive years and may have a biennial or greater reproductive cycle. Snakes returned to the hibernaculum in early September and remained active until early October. The behaviour of snakes in a field enclosure in response to time of day and body temperature (T b ) was recorded during the spring, summer, and fall. Significant differences in the T b values of sunning, movement, and shading behaviours were noted. Gravid females were significantly more active in all seasons. However, no significant difference in mean T b was found between males and females in the field, enclosure study, or laboratory thermal gradient. The observed greater level of activity may reflect the high energy demands of gravid females.