The Biogeographical Mosaic of North American Crotalids

North America represents a global centre of evolutionary radiation for rattlesnakes, spanning two primary genuses: Crotalus and Sistrurus. This diversity is not merely a matter of taxonomy but an intricate map of adaptation to extreme environments. From the high-altitude forests of the Rockies to the sun-scorched Sonoran Desert and the humid pine barrens of the Atlantic Coast, rattlesnakes have evolved specialised morphological and physiological traits to thrive. The Southwest serves as the continental epicentre, where up to 13 species may overlap in a single state, creating complex ecological niches and unique toxicological challenges for clinicians. Understanding these regional intersections is critical, as venom composition often varies significantly even within a single species across different geographical ranges. As urban sprawl encroaches upon these habitats, human-snake encounters are becoming more frequent, demanding a more nuanced public understanding of these vital predators. This geographical variance is particularly evident in species like the Timber Rattlesnake, which exhibits distinct venom types (A, B, or C) depending on whether it inhabits the coastal plains or the Appalachian highlands.