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Genus/Species

 

Crotalus spp. (without Crotalus durissus sspp.), Rattlesnakes

Species

  • 1. Crotalus adamanteus
  • 2. Crotalus angelensis
  • 3. Crotalus aquilus
  • 4. Crotalus armstrongi
  • 5. Crotalus atrox
  • 6. Crotalus basiliscus
  • 7. Crotalus campbelli
  • 8. Crotalus catalinensis
  • 9. Crotalus cerastes
  • 10. Crotalus cerberus
  • 11. Crotalus culminatus
  • 12. Crotalus enyo
  • 13. Crotalus ericsmithi
  • 14. Crotalus estebanensis
  • 15. Crotalus horridus
  • 16. Crotalus intermedius
  • 17. Crotalus lannomi
  • 18. Crotalus lepidus
  • 19. Crotalus lorenzoensis
  • 20. Crotalus mitchelli
  • 21. Crotalus molossus
  • 22. Crotalus morulus
  • 23. Crotalus oreganus
  • 24. Crotalus ornatus
  • 25. Crotalus polisi
  • 26. Crotalus polystictus
  • 27. Crotalus pricei
  • 28. Crotalus pusillus
  • 29. Crotalus pyrrhus
  • 30. Crotalus ravus
  • 31. Crotalus ruber
  • 32. Crotalus scutulatus
  • 33. Crotalus simus
  • 34. Crotalus stejnegeri
  • 35. Crotalus stephensi
  • 36. Crotalus tancitarensis
  • 37. Crotalus thalassoporus
  • 38. Crotalus tigris
  • 39. Crotalus tlaloci
  • 40. Crotalus tortugensis
  • 41. Crotalus totonacus
  • 42. Crotalus transversus
  • 43. Crotalus triseriatus
  • 44. Crotalus tzabcan
  • 45. Crotalus viridis
  • 46. Crotalus willardi

 

Crotalus exsul is now = Crotalus ruber, Sistrurus ravus is now = Crotalus ravus (Campbell and Lamar 2004).

The former subspecies of Crotalus durissus from Mexico and Central America are now defined as new species (Campbell and Lamar 2004): Crotalus durissus totonacus = Crotalus totonacus. Crotalus durissus tzabcan, Crotalus durissus durissus (Central American populations) and Crotalus durissus culminatus = Crotalus simus.

Wüster et al. (2005) suggest that the subspecies Crotalus simus tzabcan and Crotalus simus culminatus should be defined as distinct species (Crotalus tzabcan and Crotalus culminatus).

Grismer (1999) raises some subspecies on the islands in the Gulf of Mexico into full species status: Crotalus angelensis, Crotalus estebanensis, Crotalus lorenzoensis.

Crotalus tortugensis is also synonymed with Crotalus atrox by various authors.

Some authors suggest full species status for the neotropical rattlesnake Crotalus durissus vegrandis: Crotalus vegrandis

Taxonomy

Serpentes; Viperidae; Crotalinae

Common names

Rattlesnakes, Klapperschlangen

  • 1. Eastern diamondback rattlesnake
  • 2. Isla Angel rattlesnake, Angel-Klapperschlange
  • 3. Queretaro dusky rattlesnake
  • 4. Mexican dusky rattlesnake
  • 5. Western diamondback rattlesnake
  • 6. Mexican West Coast rattlesnake
  • 8. Santa Catalina rattlesnake
  • 9. Sidewinder
  • 10. Arizona black rattlesnake, Schwarze Arizona Klapperschlange
  • 11. Northwestern neotropical rattlesnake
  • 12. Baja California rattlesnake
  • 13. Guerreran long tailed rattlesnake, Cascabel Cola-larga de Guerrero
  • 14. San Esteban Island rattlesnake, San Esteban-Klapperschlange
  • 15. Timber rattlesnake
  • 16. Mexican small-headed rattlesnake
  • 17. Autlan rattlesnake
  • 18. Rock rattlesnake
  • 19. San Lorenzo Osland rattlesnake
  • 20. Speckled rattlesnake
  • 21. Black-tailed rattlesnake
  • 22. Tamaulipan rock rattlesnake
  • 23. Western rattlesnake
  • 25. Horsehead Island speckled rattlesnake
  • 26. Mexican lance-headed rattlesnake
  • 27. Twin-spotted rattlesnake
  • 28. Tancitaran dusky rattlesnake
  • 29. Southwestern speckled rattlesnake, Südwestliche gefleckte Klapperschlange
  • 30. Mexican pygmy rattlesnake
  • 31. Red diamond rattlesnake
  • 32. Mohave rattlesnake
  • 33. Middle American rattlesnake
  • 34. Long-tailed rattlesnake
  • 35. Panamint rattlesnake, Panamint-Klapperschlange
  • 38. Tiger rattlesnake
  • 40. Tortuga Island diamond rattlesnake
  • 41. Totonacan rattlesnake
  • 42. Cross-banded mountain rattlesnake
  • 43. Mexican dusky rattlesnake
  • 44. Yucatan neotropical rattlesnake
  • 45. Prairie rattlesnake
  • 46. Ridge-nosed rattlesnake

 

 


  Fig. 4.73 Crotalus horridus




  Fig. 4.74 The rattle of a rattlesnake

 

Distribution

USA (C. viridis as far as southwest Canada) Mexico and Central America. See link "Distribution" at the top of the page for detailed information.


  Map 58 Crotalus spp. (excluding C. durissus sspp.)

 

Biology

The most distinctive characteristic of this most famous group of pitvipers is the rattle on the end of the tail (Fig. 4.73). Beside Crotalus species, only the genus Sistrurus spp. has a rattle. It is not present in C. catalinensis.

The rattle consists of loosely interlocked, modified end-segment scales on the tip of the tail (Fig. 4.74). Each time a rattlesnake sheds its skin, a new segment is added. The whirring sound produced by the rattle serves as a warning signal for potential enemies.

Rattlesnakes generally have a stout body, similar to the heavy African Bitis species, with a wide, comparatively short head and wide snout. Basic colouring more or less corresponds to the surrounding soil and varies between shades of brown, grey, yellow and red. There is frequently a pattern of larger, dorsal blotches, rhombi or cross bands.

With a length of 1.5 m and more, C. adamanteus, C. basiliscus and C. atrox are amongst the largest species. Smaller species such as C. intermedius, C. pricei or C. transversus barely reach more than 60 cm.

Habitats primarily in arid areas, from the lowlands to mountains or high plateaus: C. cerastes in deserts and semi-deserts (side-winder, see Echis spp.); C. horridus in wooded, rocky uplands in the northern part of their distribution area and in swamps as well as lower-lying forests in the south; C. basiliscus in dry forests; C. adamanteus in coastal lowlands; C. viridis with 9 subspecies the most widely distributed species, is native to the whole of the West in the USA, and in the Sierra Nevada can be found up to an altitude of 4,000 m.

When threatened, rattlesnakes either rely on their camouflage colouring or try to flee. If these methods are unsuccessful, they use their rattle as a warning (but not in every case!). If they are still approached too closely, they strike rapidly and defensively from a tightly coiled, S-shaped position.

Risk

In the USA, rattlesnakes are responsible for the majority of venomous snakebites and a large proportion of fatalities. With an estimated rate of 8–12 deaths a year, 85–90% of fatalities are due to Crotalus sp. Most accidents occur in the southern states (Minton and Rutherford-Minton 1969, Russell 1991).

The most dangerous species, which cause the majority of rattlesnake bites in the USA, are C. adamanteus, C. atrox, C. horridus and C. viridis. C. atrox in particular (large species, large distribution area, quick to strike, relatively potent venom) belongs to the medically most significant species in North America. C. scutulatus and C. basiliscus cause fewer accidents, but have very potent venom.

Crotalus species are very popular amongst terrarium owners in Europe and the USA and, as a consequence, are quite commonly the cause of severe envenoming in snake owners. A recent study in Arizona showed that more than half the snakebites there (in particular Crotalus bites) were self-inflicted, i.e. the bites were a result of attempts to approach or handle snakes. Alcohol was involved in more than 50% of these "illegitimate bites" (Curry et al. 1989).

There are hardly any epidemiological or clinical data available from Mexico.

Literature (biological)

Alvarado-Diaz and Campbell 2004, Bryson et al. 2014, Campbell and Lamar 1989, 2004, Campbell and Flores-Villela 2008, Davis et al. 2016, Grismer 1999, Klauber 1972, Meik et al. 2018, Quijada-Mascarenas and Wüster 2006, Russell 1983, Wallach et al. 2014, Wüster et al. 2005