Prairie Rattlesnake (Crotalus viridis)

Upon visiting the hibernaculum in the grasslands national park here in Canada, we stumbled across 50 or more rattlesnakes like this one, As summer ends, up to 1000 rattlesnakes all venture back to these over wintering places where they go underground and intertwine with each other. Other snake species also use the same caves including bull snakes, garter snakes and racers. In days (hopefully) gone farmers used to blow these hibernaculums up with dynamite effectively killing up to 1000 snakes at once and leaving up to 10km square snake free. (not hard to eliminate a species that way eh?