Crotalus is a genus of venomous pit vipers commonly called rattlesnakes. Members of this group are best known for the segmented, keratinous rattle at the tip of the tail, which produces a characteristic buzzing sound when vibrated. The name derives from the Greek krotalon, meaning "rattle." Today the genus contains a number of species—currently recognized as 29—that occupy a wide variety of habitats across the Americas. For a taxonomic overview see genus information.
Physical characteristics
Rattlesnakes in the genus Crotalus share several distinctive anatomical features. These include:
- a series of interlocking rattle segments made of keratin at the tail tip;
- heat-sensitive pit organs between each eye and the nostril that detect infrared radiation, aiding in prey detection;
- solenoglyphous fangs—long, hollow, retractable fangs used to inject venom.
Range and habitat
Crotalus species are native to the New World, with a range extending from southern Canada through the United States and Mexico and into Central and South America as far as northern Argentina. They occupy deserts, grasslands, rocky hillsides, forests and some high-elevation zones. For maps and regional details consult the distribution resources and regional species accounts.
Behavior, diet and reproduction
These snakes are generally ambush predators that feed on small mammals, birds, amphibians and occasionally other reptiles. Activity patterns vary by species and climate: some are primarily diurnal, others crepuscular or nocturnal. Most Crotalus give birth to live young (a reproductive mode often described as ovoviviparity or viviparity), and litter sizes vary by species and maternal size.
Venom and medical importance
Venom composition varies among species and populations but is typically rich in proteins that cause local tissue damage, disrupt blood clotting and impair circulation. Certain species, such as the Mojave rattlesnake (Crotalus scutulatus), are noted for neurotoxic components in addition to hemotoxic effects. Bites can be serious and require prompt medical attention and, when appropriate, administration of antivenom. General information on pit vipers and envenomation treatment is available at pit viper resources and clinical guides.
Taxonomy, conservation and notable facts
Crotalus belongs to the subfamily Crotalinae (pit vipers) within the family Viperidae. Closely related genera include Sistrurus, which contains smaller 'pygmy' rattlesnakes that differ in scalation and head proportions. Conservation concerns for many rattlesnake populations include habitat loss, road mortality, intentional killing and illegal collection. Some species are assessed under regional or international conservation frameworks; for further reading on species lists and protection measures see the species checklist and conservation resources.