Mojave Rattlesnake
Crotalus scutulatus
Photo taken hear Hillside, Arizona as a group of 7 naturalists admired its aggresive stance while encouraging it to move off of the roadway for its own safety. It was about 2/3 of a meter in length, and appeared to be carrying a recent meal within its abdomen. The rattle sound was loud and convincing.
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My first impression of this snake was Western Diamondback (Crotalus atrox). However, it was pointed out to me by Jorge, a snake specialist and visitor to this page, that in this specimen the white bands on the tail are wider than the black, a characteristic of the Mojave. Also it appears that the pale diagonal line from just behind the eye, reaches a point posterior to the corner of the mouth. The most definitive characteristic separating the Mojave from the Western Diamondback are a pair of large scales between the supraoculars on the snout. I zoomed in on the snout area with my image program, but the resolution was insufficient to see individual scales. Next time I will have to get a little closer yet, before I snap the shutter release!
On the other hand, Val Buckner offers the following analysis:
Having collected numerous Mojaves from the east Mojave area, where they have a consistantly green background coloration (although none personely from the Ariz. area, where it seems color and pattern can vary quite a bit) I'm going to have to dispute the ID and say the snake pictured is an atrox due to the extreme contrast between the tail bands (stark white & jet black) which is extremely rare in the Mojave but definitive of the Atrox, although as mentioned, the band spacing is similiar to the Mojave. The Mojave's tail band(s) do not generally encircle the tail as the Atrox's do and as the terminus band(s) appear to do in the photo. The head also appears to be rather large in relation to body length and girth which is an atrox trait, where as the Mojaves tend to have a smaller , narrower head compared to most of the Crotalus species. A hybrid possibly.
The Mojave Rattlesnake besides inhabiting the Mojave Desert also is common in the Sonoran And Chihuahuan Deserts. Creosote flats are a frequent habitat where they hunt almost exclusively at night.