u/Crotalus

A large Veracruz Neotropical Rattlesnake (Crotalus mictlantecuhtli) from a trip to Mexico a few years ago. This species was recently recognized as a separate lineage of the Neotropical Rattlesnakes, described in 2020, about a year before this photograph was taken.

Carbajal Márquez, Rubén & Cedeño-Vázquez, José & Martinez, Arely & Neri, Edgar & Machkour-M’Rabet, Salima. (2020). Accessing cryptic diversity in Neotropical rattlesnakes (Serpentes: Viperidae: Crotalus) with the description of two new species. Zootaxa. 4729. 451-481. 10.11646/zootaxa.4729.4.1.

Twin Spotted Rattlesnakes (Crotalus pricei) are small, high-elevation rattlesnakes that are found in a handful of mountain ranges in the Sky Islands region of Arizona and northern Mexico. They are occasionally seen by hikers on high saddles and trails, where they are quick to flee with a departing buzz. A person would really have to pick one up or be hiking barefoot to get bitten by one, if they're even lucky enough to see one or have it stick around long enough for that to happen.

Southwestern Speckled Rattlesnakes (Crotalus pyrrhus) are commonly seen by hikers in the Phoenix area at popular parks, even those entirely within the city. They have a relatively extreme level of camouflage for a rattlesnake, and many people are surprised to learn just how many rattlesnakes they walk by even at the most heavily-hiked parks in the city. This is one of several hundred that inhabit one of these parks, found on a hillside below a trail.

A Southwestern Speckled Rattlesnake (Crotalus pyrrhus) in ambush along a ledge in central Arizona. While most of the boulder field where it was found is made of rock similar to how this snake looks ... this particular large boulder made of light colored granite helped make this one easy to spot. We got some photos from a distance and left it there to hopefully succeed in getting that chuckwalla or ground squirrel it's looking for.

Torre de Guatel Arborial Alligator Lizard (Abronia meledona) in Guatemala we found a few years ago.

One of several Western Striped Forest Pitvipers (Bothrops bilineatus smaragdinus) we found in Peru earlier in the year. This was the largest of the group, found coiled in vines just overhead.

When I first started looking for this species, I mistakenly thought I was looking a snake in a typical arboreal viper pose, wrapped down branches or in a down-facing ambush position ... like a Bothreichis or Trimeresurus ... and I didn't find any with that search image. All of these that I've seen in ambush positions sit in a coil in vegetation like other Bothrops do, which I should have guessed in retrospect. Having that image to search for, they became easier to find after that.

An Arizona Black Rattlesnake (Crotalus cerberus) from the southern extent of their range.

A brilliantly colored Eastern Collared Lizard from the eastern edge of Arizona. This one watched us carefully from atop low boulders along an otherwise flat field, and allowed a single photograph before it disappeared.

We met this Caspian Cobra (Naja oxiana) in the grassy hills of eastern Uzbekistan.

This cobra may have the most lethal venom of all cobras ... but its venom also shows potential to be an effective treatment for some cancers.

Ebrahim K, Vatanpour H, Zare A, Shirazi FH, Nakhjavani M. Anticancer Activity a of Caspian Cobra (Naja naja oxiana) snake Venom in Human Cancer Cell Lines Via Induction of Apoptosis. Iran J Pharm Res. 2016 Winter;15(Suppl):101-112. PMID: 28228809; PMCID: PMC5242357.

A Southwestern Speckled Rattlesnake (Crotalus pyrrhus) resting in a small cave during the hottest time of the year. This location receives almost no sun, due to its depth and aspect, which makes it an ideal aestivation site.

Snakes, as do other ectothermic (cold-blooded) animals, do regulate their body temperature by managing external forces. It's more than just basking in the sun ... they also spend a lot of time and energy trying to stay cool. For animals in Arizona, that can be a challenge. These sites, where they return each year when temperatures become lethal, are just as important as a winter hibernation den for rattlesnakes in cooler areas.

Banded Rock Rattlesnakes (Crotalus lepidus klauberi) are common in several of the sky islands of southeastern Arizona. They're smaller than most expect a rattlesnake to be, with most that I've encountered being less than two feet long. They're also strongly sexually dimorphic, which is not common in rattlesnakes. Males, like this one, often develop bright, metallic greens on their bodies, which matches the common lichen found on rocks where they live. This one that we found was exceptional.

A New Mexico Ridgenosed Rattlesnake (Crotalus willardi obscurus) from Mexico. I am lucky to be working with this rattlesnake as part of an international conservation effort.

A Twin Spotted Rattlesnake (Crotalus pricei) that we found in eastern Arizona, showing off many more than "twin" spots. These tiny rattlesnakes can vary greatly in appearance from one location to the next, even between individuals in a single population. These are not likely to be seen unless you are spending time in the highest areas of a handful of the Chiricahua, Huachuca, Pinaleño, or Santa Rita mountain ranges.

Prival, D. B., Goode, M. J., Swann, D. E., Schwalbe, C. R. (2002), & Schroff, M. J.. Natural History of a Northern Population of Twin-Spotted Rattlesnakes, Crotalus pricei. Journal of Herpetology, 36(4), 598–607.

DOI: https://doi.org/10.1670/0022-1511(2002)036[0598:NHOANP]2.0.CO;2

A mature Black-tailed Rattlesnake we found on a late-night hike near Phoenix. These snakes live in mountainous or hilly areas, where they are often confused with a number of other rattlesnake species.

A pretty little Arizona Ridgenosed Rattlesnake (Crotalus willardi willardi) from a humid week in southeastern Arizona.

This tiny whipsnake (Chironius sp.) we saw in Peru is basically a long life support system for eyes. It's likely less cute to the many lizards and frogs in the region.

I found a Rosy Boa that had apparently lost its tail somewhere along the way. This is one of two species of boa native to Arizona, found in rocky areas in the west-southwestern third or so of the state.

I met this Gila Monster out and about on a spring day in 2023. At the time, there were a lot of quail eggs and baby cottontails to find out there, which gets these animals active and observable.

These animals are the only venomous lizard in the United States, and one of five species of the Heloderma genus found across Central America.