Crotalus tigris

The traditional view of rattlesnake taxonomy that recognizes the two monophyletic sister genera Crotalus and Sistrurus (e.g. Brattstrom 1964) has recently been challenged. Stille (1987) and McCranie (1988) presented data that suggested Sistrurus is not monophyletic and rendered Crotalus paraphyletic. Parkinson (1999) found Sistrurus monophyletic but its position rendered Crotalus paraphyletic. Knight et al. (1993) used mtDNA to defend the traditional generic taxonomy, but in order to do so ignored the most parsimonious tree. The genus Crotalus is monophyletic when including the Mexican C. ravus (Murphy et al. 2002), and is supported as such in most recent phylogenies, as well as being the sister taxon to a monophyletic Sistrurus (e.g., Pyron et al. 2013) (Crother 2017).

The range extends from central Arizona south through south-central Arizona (Lowe et al. 1986; east to about 47 kilometers east of Douglas: Painter and Milensky, 1993, Herpetol. Rev. 24:155-156; Howland et al., 2002, Herpetol. Rev. 33:149) to southern Sonora, Mexico, including Isla Tiburon in the Gulf of California, at elevations from sea level to about 4,800 feet (1,465 meters) (Stebbins 2003, Campbell and Lamar 2004). Reported occurrences at higher elevations have not been confirmed (Campbell and Lamar 2004).

On a range-wide scale, Campbell and Lamar (2004) mapped 33 collection sites. Lowe et al. (1986) stated that the species is known from approximately 100 localities throughout the range.

Southern populations on the flatter areas of the coastal plain of Sonora are probably losing habitat due to the intensification of agriculture. Overall, however, this species is not seriously threatened.