Mohave Greens are notorious for being the nastiest and deadliest snakes in the West. But is the reputation of the Mohave rattlesnake (Crotalus scutulatus) deserved? Click on the myths to learn the facts about Mohave rattlesnakes.

 

Mojave or Mohave?

According to the three major herpetological societies in the United States (American Society of Ichthyologists and Herpetologists, Herpetologists’ League, and Society for the Study of Amphibians and Reptiles), the standardized English name is Northern Mohave Rattlesnake and the scientific name is Crotalus scutulatus or Crotalus scutulatus scutulatus,1 if you consider our Mohaves to be a subspecies distinct from the Mexican rattlesnake Crotalus scutulatus salvini. According to linguists, the English word Mohave can be spelled with either an “h” or a “j.”2

Mythical Mohave Rattlesnake

The definitive way to identify a Mohave rattlesnake: they have fewer, larger scales between their eyes than other rattlesnakes.

Myth: There are rattlesnakes, and then there are Mohave Greens.

Fact: Mohave rattlesnakes are no more dangerous than any of the nearly 50 species of rattlesnake. Mohave greens are just Mohave rattlesnakes with a greenish tint, and are no more toxic or aggressive than any other Mohave. The name is colloquial, and is often mis-applied to other species, such as black-tailed and western diamond-backed rattlesnakes. Numerous genetic studies show that Mohaves are most closely related to the Prairie and Western Rattlesnakes, Crotalus viridis and Crotalus oreganus, respectively.3

 

Mythical Mohave Rattlesnake

A safer way to identify: Mohaves generally have more white between the black band on their tails.

Mythical Mohave Rattlesnake

Tail of a western diamondback rattlesnake.

Myth: Mohave Rattlesnakes were unknown until just a few decades ago.

Fact: Like other rattlesnakes, Mohaves have been evolving for millions of years. Genetic evidence strongly suggests that Mohave Rattlesnakes diverged from an ancestor shared with Crotalus viridis and Crotalus oreganus before those lineages separated from one another between 26.4 and 3.9 million years ago.3

The myth that Mohave Rattlesnakes have no scientific history and no “type specimen” (the preserved animal used for the original description of a species) has been fueled by an error in a publication in 1900,4 causing Laurence Klauber to correctly point out in 1956 that the type specimen designated for Crotalus scutulatus was not the correct species.5 That confusion has recently and conclusively been resolved: the type specimen for Crotalus scutulatus resides in the preserved collection of the Academy of Natural Sciences of Philadelphia as specimen number ANSP 7069.6

Myth: All Mohaves have strongly neurotoxic venom.

Fact: Like other rattlesnakes, the venom of Mohaves is incredibly complex and variable. Many Mohaves produce a potent neurotoxin called Mojave toxin but lack the tissue-destroying components found in many other rattlesnake venoms. However, some Mohaves produce a venom that destroys tissue but lacks Mojave toxin and others produce venom with both components. This was first carefully described, including a map, in 1991.7 A more recent study further describes variation in Mohave Rattlesnake venom in southern Arizona.8

To be fair, we now know that the venoms of many rattlesnake species contain neurotoxins that are molecularly similar to Mojave Toxin, including the Midget Faded Rattlesnake (Crotalus viridis concolor), the Canebrake Rattlesnake (Crotalus horridus atricaudatus) and the tropical rattlesnakes Crotalus durissus and Crotalus vegrandis,9 as well as the Southern Pacific Rattlesnake (Crotalus oreganus helleri) in California.10 Indeed, neurological signs and symptoms following some snakebites in coastal southern California have repeatedly prompted naïve medical experts to diagnose Mohave Rattlesnake envenomation in areas far from where Mohaves live.

Myth: Mohaves are the most deadly rattlesnake.

Fact: Human fatalities from Mohave rattlesnake bites are very rare. The last known fatality was in 2007, likely due to an anaphylactoid reaction. Such reactions are extraordinarily rare and not limited to Mohave bites. Neither a study of 15 confirmed Mohave Rattlesnake bites in Arizona11 nor another study of 159 snakebite patients in the Tucson area, in which 30% were estimated to be Mohave Rattlesnake bites,12 produced any deaths. A recent study of 516 rattlesnake bites in Cochise and Pima counties documented one fatality, with the species responsible not verified.8

The deadly reputation of Mohave rattlesnakes is traceable to venom studies in the lab, where their venom routinely ranks as one of the most lethal to mice. Such studies do not always translate well to humans.

Myth: There is no treatment for Mohave bites.

Fact: Mohave rattlesnake bites are treatable with the same antivenom and procedure used for other rattlesnakes. Both antivenoms available in US hospitals neutralize Mojave toxin.

Myth: Mohave rattlesnakes are aggressive, and will attack and chase people.

Fact: Rattlesnakes want nothing to do with people and Mohaves are no different. A large Mohave might weigh two pounds. Now imagine confronting an animal 50-100 times more massive than you. Would you attack? Of course not! You’d be scared to death. First you might try to hide, but if that didn’t work, you might try to look and act as big and dangerous as possible. Only as a last resort would you fight — probably kicking, scratching, and biting to get away. Rattlesnakes are no different… except they cannot kick or scratch.

Most snakebites happen to people who handle or try to kill a snake. The rest are due to people putting their hands and feet where they can’t see or don’t look. Watching where you place your hands and feet and leaving rattlesnakes alone would prevent virtually all rattlesnake bites.

 

Mythical Mohave Rattlesnake

How most people picture Mohave rattlesnakes, rattling and in a defensive posture.

Mythical Mohave Rattlesnake

This is how we actually encountered that individual Mohave; peacefully resting under a bush until we scared him by pulling him out into the open for pictures (shame on us).

In our thousands of encounters with Mohaves and other rattlesnakes, we’ve never observed an attack and have found rattlesnakes to be rather timid creatures. We’ve seen snakes appear to chase or attack in two situations: a mother protecting her babies or a snake trying to escape to shelter behind us. These days, everyone has a video camera in their pocket… yet we still await video proof of an unprovoked rattlesnake attack!

Myth: Mohave rattlesnakes are expanding their range in New Mexico.

Fact: There are only a few isolated populations in southern New Mexico. None of the Mohave rattlesnake sightings outside these areas in New Mexico have been confirmed, so if you have a photo or video of one — please share it!

 

Observations of Mohave rattlesnakes in New Mexico

Confirmed observations of Mohave rattlesnakes in New Mexico (red dots).

Did we miss any myths or questions you have about Mohaves? Let us know.


References

  1. Crother, B.I., et al. 2012. Scientific and Standard English and French Names of Amphibians and Reptiles of North America North of Mexico, with Comments Regarding Confidence in our Understanding. (7th ed) Herpetological Circular #39, Society for the Study of Amphibians and Reptiles.
  2. Sherer, L.M. 1967. The name Mojave, Mohave: A history of its origin and meaning. Southern California Quarterly. 49:1–36.
  3. Douglas, M.E., et al. 2002. Phylogeography of the Western Rattlesnake (Crotalus viridis) complex, with emphasis on the Colorado Plateau. Pp. 11–50 In: G.W. Schuett, et al. (Eds.), Biology of the Vipers. Eagle Mountain Publishing, Eagle Mountain, Utah.
  4. Cope, E.D. 1900. The crocodilians, lizards, and snakes of North America. Pp.153–1270 + 36 pls. In Report of the U.S. National Museum for the Year Ending June 30, 1898. Government Printing Office, Washington, DC.
  5. Klauber, L.M. 1956. Rattlesnakes – Their Habits, Life Histories, and Influence on Mankind, 2 vols. University of California Press, Los Angeles and Berkeley.
  6. Cardwell, M.D., et al. 2013. Type specimen of Crotalus scutulatus (Chordata: Reptilia: Squamata: Viperidae) re-examined, with new evidence after more than a century of confusion. Proceedings of the Biological Society of Washington. 126:11–16.
  7. Wilkinson, J.A., et al. 1991. Distribution and generic variation in venom A and B populations of the Mojave rattlesnake (Crotalus scutulatus scutulatus) in Arizona. Herpetologica. 47:54–68.
  8. Massey, D.J., et al. 2012. Venom variability and envenoming severity outcomes of the Crotalus scutulatus scutulatus (Mojave rattlesnake) from Southern Arizona. Proteomics 75:2576-2587.
  9. Doley, R., et al. Snake venom phospholipase A2 enzymes. Pp. 173–206 In: S.P. Mackessy (ed). Handbook of Venoms and Toxins of Reptiles. CRC Press, Boca Raton, Florida.
  10. French, W.J., et al. 2004. Mojave toxin in venom of Crotalus helleri (Southern Pacific Rattlesnake): molecular and geographic characterization. Toxicon. 44:781–791.
  11. Hardy, D.L. 1983. Envenomation by the Mojave Rattlesnake (Crotalus scutulatus scutulatus) in southern Arizona, U.S.A. Toxicon. 21:111–118.
  12. Hardy, D.L. 1985. Rattlesnake envenomation in Tucson, Arizona: 1973–1980. Toxicon. 23:573.
  13. Cardwell, M.D. 2008. The reproductive ecology of Mohave rattlesnakes. Journal of Zoology. 274: 65–76.
  14. Cardwell, M.D. 2013. Behavioral Changes by Mohave Rattlesnakes (Crotalus scutulatus) in Response to Drought. Unpublished thesis, California State University, Sacramento.

 

Updated September 2019 by: Michael D. Cardwell (Biologist & Mohave Advocate), Melissa Amarello (Executive Director of ASP), and Jeffrey J. Smith (Director of Research of ASP).