This is a 'northern black tailed' rattlesnake, Crotalus molossus molossus. It's range includes portions of southern and central Arizona, southern New Mexico and southwestern Texas and adjacent Mexico (Connant 1975). In the eastern aspect of its range, it inhabits the wooded canyons, cliffs and rock piles in the west-central Edwards Plateau, and the adjacent Chihuahuan Desert. Though present only in the southwestern extreme of the hurricane prone region of North America (Tennant, 1998), it is of importance to those living in these regions, and first-responders offering aid to those affected by such a disaster.Typically a mild tempered rattlesnake, it still packs moderate, to large amounts of potent venom. Because of apparent antigenic differences in black tailed rattlesnake venom, treating bites with 'CroFab' antivenin can require comparatively larger doses than bites of other rattlesnake species (Consroe et al., 1995; Sanchez et al 2003a, 2003b; Yarema and Curry, 2005)
CDC/ Edward J. Wozniak D.V.M., Ph.D.
October 31, 2012