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Southwestern Speckled Rattlesnake (Crotalus pyrrhus)

[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column][/vc_row][vc_row][vc_column width=”1/2″][vc_single_image image=”1222″ img_size=”large” alignment=”center” style=”vc_box_rounded”][vc_column_text]Southwestern Speckled Rattlesnake, Phoenix Mtn Parks. Photo by Jim Rorabaugh[/vc_column_text][/vc_column][vc_column width=”1/2″][vc_row_inner][vc_column_inner width=”1/2″][vc_single_image image=”2743″ img_size=”medium” alignment=”center” onclick=”img_link_large”][vc_column_text]Southwestern Speckled Rattlesnake, Maricopa County, AZ. Photo by Jim Rorabaugh[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][vc_column_inner width=”1/2″][vc_single_image image=”2745″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Southwestern Speckled Rattlesnake, Maricopa County, AZ. Photo by Jim Rorabaugh[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][/vc_row_inner][vc_row_inner][vc_column_inner width=”1/2″][vc_single_image image=”2744″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Southwestern Speckled Rattlesnake, Phoenix Mountain Park. Photo by Jim Rorabaugh[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][vc_column_inner width=”1/2″][vc_single_image image=”2746″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Southwestern Speckled Rattlesnake, Maricopa Co., AZ. Photo by Jim Rorabaugh[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][/vc_row_inner][vc_row_inner][vc_column_inner width=”1/2″][vc_single_image image=”2747″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Southwestern Speckled Rattlesnake climbing in a Ratany (Krameria sp.), South Mountain, Maricopa Cnty, AZ. Photo by Jim Rorabaugh[/vc_column_text][/vc_column_inner][/vc_row_inner][/vc_column][/vc_row][vc_row][vc_column width=”1/6″][/vc_column][vc_column width=”2/3″][vc_column_text]

Description

The Southwestern Speckled Rattlesnake (Crotalus pyrrhus) is a pit viper of moderate size (< 1370 mm, but most are <1000 mm total length (TL)). As with other Crotalus, it has vertically elliptical pupils, a heat-sensing pit between the eye and nostril on each side, and prominent rattles on the tail. The Speckled Rattlesnake is highly variable in dorsal background color, including gray, blue-gray, tan, yellowish-pink, orange, and cream. Background color often, but not always, resembles the color of the rocks in the snake’s habitat. From 23 to 46 dark crossbands, which often narrow laterally and may form blotches anteriorly, overlay the background color on the body. Another 3-9 dark crossbands are found on the tail. Crossbands are vague in some specimens and regions, and each crossband is often split by a lighter, central area. Dorsal scales are keeled, in 21-27 rows at mid-body, and speckled. The rostral scale is separated from the anterior nasal scales by one or more small scales. The upper preocular scales are divided. Commonly there are two loreals per side, but that number varies from none to five. The anal plate is undivided (Lemm 2006, Ernst and Ernst 2012, Meik 2016).

Males on average have more dark tail bands than females and slightly longer tails as a proportion of total length. Males also average fewer ventral scales but more subcaudals than females. Newly born snakes resemble the adults, but are 143-305 mm TL (Ernst and Ernst 2012).

This taxon was until very recently considered a subspecies of the Speckled Rattlesnake (Crotalus mitchellii). Five subspecies of C. mitchellii have been recognized (McCrystal and McCoid 1986).  The Panamint Rattlesnake (Crotalus mitchellii stephensi) of eastern California and southern Nevada, was elevated to species by Douglas et al. (2007). Grismer (2002) considered the subspecies C. m. angelensis and C. m. muertensis, endemic to islands in the Gulf of California, as full species, but that arrangement was not universally accepted (Campbell and Lamar 2004). Using mitochondrial and nuclear DNA analyses, Meik et al. (2015) elevated C. m. angelensis, C. m. pyrrhus, and C. m. mitchelli to species.  Of the former C. mitchellii subspecies, only C. pyrrhus occurs in Arizona. 

In our area, the Southwestern Speckled Rattlesnake is most likely to be confused with the Tiger Rattlesnake (Crotalus tigris). The latter species has proportionally larger rattles and a smaller head than the Southwestern Speckled Rattlesnake, it is typically banded towards the anterior of the body (although bands on and near the neck may form blotches), the basal rattle segment is tan or brown (black in the Southwestern Speckled Rattlesnake), the rostral scale contacts the nasals, and the upper preocular scales are undivided.  The Southwestern Speckled Rattlesnake’s distribution is more western and southwestern in Arizona, whereas the Tiger Rattlesnake is found in the south-central portion of the state. However, both occur in the Cave Creek and Carefree area, Piestewa Peak, the North Maricopa Mountains, South Mountain, Sierra Estrella, Sand Tank Mountains, and likely elsewhere in south-central Arizona.

Throughout its range, the Southwestern Speckled Rattlesnake occurs in southern California, western Arizona, southern Nevada, extreme southwestern Utah, northwestern Sonora, and the northern Baja California Peninsula.  It also occurs on Islas Smith, El Piojo, Angel de la Guarda, and Cabeza de Caballo in the Gulf of California (Meik et al. 2015).

In the 100-Mile Circle, this is a snake of rocky, Sonoran Desert Mountain ranges, in both the Arizona Upland and Lower Colorado River subdivisions of the Sonoran Desert. Most of the range of the species is outside of the 100-Mile Circle. It is only known to occur in a few northwestern mountain ranges of the Circle, including the Sand Tank Mountains, Sierra Estrella, South Mountain and a few of the other urban mountain parks in Phoenix (Piestewa Peak, Shaw Butte, North Mountain, and Stony Mountain), and the Queen Creek area. It may occur in the northwestern portions of the Tohono O’odham Nation. Elevational range in Arizona is approximately 100-1615 m (Meik 2016). Elsewhere, the Southwestern Speckled Rattlesnake also occurs in Mojave desertscrub, chaparral, and pinyon-juniper woodlands up to at least 1646 m elevation (Loomis and Stephens 1967, Ernst and Ernst 2012). Individuals are occasionally encountered far from rocky areas (Gartner and Reiserer 2003). I once found a Southwestern Speckled Rattlesnake on the eastern edge of the Algodones Dunes, Imperial County, California, that was at least 5.0 km from the nearest rocky terrain.  Southwestern Speckled Rattlesnakes are capable climbers, and have been found as much as 90 cm up into vegetation (Klauber 1972, e.g. see the image gallery).

Activity in the 100-Mile Circle is primarily from March into October, although there is a 6 December collection from the northwestern corner of Organ Pipe Cactus National Monument, and an 18 November collection from Tinajas Altas in Yuma County. Duvall et al. (1996) reported activity in the Phoenix area in November, as well. Activity is mostly diurnal early and late in the season, with a propensity towards nocturnal activity in summer (Moore 1978). These snakes are most active in the mating season from April to early June (Glaudas and Rodríguez-Robles 2011b). Southwestern Speckled Rattlesnakes frequently congregate at den sites during winter, which are rock outcrops or subterranean rodent burrow networks. Up to 180 individuals may occupy winter dens (Klauber 1972, Lowe et al. 1986, Glaudas and Rodríguez-Robles 2011a). However, at least some individuals are solitary in winter (Duvall et al. 1996, Glaudas and Rodríguez-Robles 2011a). Individuals may emerge briefly from dens during the winter, presumably to drink water (Glaudus 2009, Glaudas and Rodríguez-Robles 2011a).

Males and females in the United States mature at about 512 and 552 mm TL, respectively (Goldberg 2000). Mating occurs in the spring (from April into mid June; Lowe et al. 1986, Glaudas and Rodríguez-Robles 2011a, Ernst and Ernst 2012). Males will engage in combat, possibly for access to females (Glaudas and Rodríguez-Robles 2011a). In southern Nevada, females were clumped around winter den sites during the mating season, whereas males traveled among den sites, presumably to find receptive females (Glaudas and Rodríguez-Robles 2011a). Gestation is about 140 days, and most litters are born from late June into September. Females do not reproduce every year. Litters contain 3-12 young (Ernst and Ernst 2012). A female collected from 12 km west of Agua Caliente, Maricopa County, gave birth to four live young on 16 September (UAZ 44316). Another female from Yellowstone Medicine Butte, Maricopa County, gave birth to five young during 2-4 September (UAZ 43946-43950). Pregnant females may aggregate at “rookeries” beginning in June and may not leave until after giving birth (Meik 2016).  A female remained with her young for several days after birth in Riverside County, California (Greene et al. 2002).

Mammals, including various rodents, ground squirrels, and rabbits, as well as lizards as large as Chuckwallas are consumed (Klauber 1972, Ernst and Ernst 2012, Glaudus and Rodriguez-Robles 2011b). Lizards are more important in the diet of juvenile snakes, compared to adults, which take primarily mammals. Birds are also taken (Meik 2016). For instance, a Goldfinch and a Willow Flycatcher were reported in the diet (Miller and Stebbins 1964, Klauber 1972). Cannibalism of juveniles by adults has been observed in captivity (Porter 1983).

Individuals of this species are of varying temperament. Some are quick to coil and rattle, whereas others, perhaps in protected sites, remain calm when approached. Lowe et al. (1986) and Meik (2016) report that Southwestern Speckled Rattlesnake venom in Arizona is of moderate toxicity, but because of the size of this snake, any bites are potentially very dangerous. Bite symptoms in humans include significant edema, discoloration around the bite, and pain. However, recovery is usually complete and uneventful after treatment with antivenin (Klauber 1972, Ernst and Ernst 2012). Goldberg et al. (2013) examined helminths in Southwestern Speckled Rattlesnake specimens.

The Southwestern Speckled Rattlesnake is listed as a species of least concern on the 2015 IUCN Red List. With a valid Arizona hunting license, four may be collected per year or held in possession alive or dead. There is no hard evidence that Southwestern Speckled Rattlesnakes are threatened in any way. However, some color morphs are desirable to collectors. The Arizona Game and Fish Department is investigating whether populations of a very light-colored morph in the Tinajas Altas Mountains, Yuma County, are being affected by collection. Although still present in a number of Phoenix Mountain Parks, Southwestern Speckled Rattlesnake numbers may be reduced near heavily urbanized areas (Duvall et al. 1996) due to collection, killing, mortality on roads, habitat fragmentation, and other factors.

Suggested Reading:

Armstrong, B.L., and J.B. Murphy. 1979. The Natural History of Mexican Rattlesnakes. University of Kansas Museum of Natural History Special Publication 5:1-88.

Brennan, T.C., and A.T. Holycross. 2006. Amphibians and Reptiles in Arizona. Arizona Game and Fish Department, Phoenix, AZ.

Campbell, J.A., and W.W. Lamar. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Cornell University Press, Ithaca, NY.

Douglas, M.E., M.R. Douglas, G.W. Schuett, L.W. Porras, and B.L. Thomason. 2007. Geneological concordance between mitochondrial and nuclear DNAs supports species recognition of the Panamint Rattlesnake (Crotalus mitchellii stephensi). Copeia 2007:920–932.

Duvall, D., J.K. O’Lieile, S.G. Heald, and S.J. Beaupre. 1996. Urban rattlesnake status and ecology. Arizona Game and Fish Department Heritage Grant #U93032, final report.

Ernst, C.H., and E.M. Ernst. 2012. Venomous Reptiles of the  United states, Canada, and Northern Mexico. Volume 2, Crotalus. Johns Hopkins University Press, Baltimore, MD.

Gartner, G.E.A., and R.S. Reiserer. 2003. Crotalus mitchellii (Speckled Rattlesnake): Mating. Herpetological Review 34:65.

Glaudas, X. 2009. Rain-harvesting by the Southwestern Speckled Rattlesnake (Crotalus mitchellii pyrrhus). The Southwestern Naturalist 54(4):518–521.

Glaudas, X., and J.A. Rodríguez-Robles. 2011a. Vagabond males and sedentary females: spatial ecology and mating system of the speckled rattlesnake. Biological Journal of the Linnean Society 103:681–695.

Glaudas, X., and J.A. Rodríguez-Robles. 2011b. A two-level problem: habitat selection in relation to prey abundance in an ambush predator, the speckled rattlesnake (Crotalus mitchellii). Behaviour 148:1491–1524.

Goldberg, S.R. 2000. Reproduction in the Speckled Rattlesnake, Crotalus mitchellii (Serpentes: Viperidae). Bulletin of the Southern California Academy of Sciences 99:101–104.

Goldberg,S.R., C.R. Bursey, and X. Glaudas. 2013. Helminths of the Speckled Rattlesnake, Crotalus mitchellii (Squamata: Viperidae). Western North American Naturalist 73(4):533–535.

Green, H.W., P.G. May, D.L. Hardy Sr., J.M. Sciturro, and T.M. Farrel. 2002. Parental behavior by vipers. Pages 179-206 in G.W. Schuett, M. Horen, M.E. Douglas, and H.W. Greene (eds), Biology of the Vipers, Eagle Mountain Publishing, Eagle Mountain, UT.

Grismer, L. 2002. Amphibians and Reptiles of Baja California Including its Pacific Islands and the Islands in the Sea of Cortes. University of California Press, Berkeley.

Lemm, J.M. 2006. A Field Guide to the Amphibians and Reptiles of the San Diego Region. California Natural History Guides, University of California Press, Berkeley.

Lowe, C.H. C.R. Schwalbe, and T.B. Johnson. 1986. The Venomous Reptiles of Arizona. Arizona Game and Fish Department, Phoenix, AZ.

McCrystal H.K., and M.J. McCoid. 1986. Crotalus mitchellii (Cope) Speckled Rattlesnake. Catalog of American Amphibians and Reptiles 388.1–4388.4.

Meik, J.M. 2008. Morphological analysis of the contact zone between the rattlesnakes C. mitchellii stephensi and C. m. pyrrhus. Pages 39–49 in Hayes, W.K., K.R. Beaman, M.D. Cardwell, and S.P. Bush (eds), The Biology of Rattlesnakes. Loma Linda University Press, Loma Linda, CA.

Meik, J.M. 2016. Southwestern Speckled Rattlesnake Crotalus pyrrhus (Cope 1867).  Pages 531-562 in G.W. Schuett, M.J. Feldner, C.F. Smith, and R.S. Reiserer (eds). 2016. Rattlesnakes of Arizona, Volume 1. ECO Herpetological Publishing, Rodeo, NM.

Meik, J.M., J.W. Streicher, A.M. Lawing, O. Flores-Villela, and M.K. Fujita. 2015. Limitations of climatic data for inferring species boundaries: insights from Speckled Rattlesnakes. PLOS/One DOI:10.1371:1-19.

Miller, A.H., and R.C. Stebbins. 1964. The Lives of Desert Animals in Joshua Tree National Monument. University of California Press, Berkeley.

Moore, R.G. 1978. Seasonal and daily activity patterns and thermoregulation in the Southwestern Speckled Rattlesnake (Crotalus mitchellii pyrrhus) and the Colorado Desert Sidewinder (Crotalus cerastes laterorepens). Copeia 1978:439–442.

Porter, T. 1983. Induced cannibalism in Crotalus mitchellii. Bulletin of the Chicago Herpetological Society 18:46.

Rubio, M. 2010. Rattlesnakes of the United States and Canada. ECO Herpetological Publishing and Distribution, Rodeo, NM.

Schuett, G.W., M.J. Feldner, C.F. Smith, and R.S. Reiserer (eds). 2016. Rattlesnakes of Arizona, Volume 1. ECO Herpetological Publishing, Rodeo, NM.

Rorabaugh, J.C., and J.A. Lemos Espinal. 2016. A Field Guide to the Amphibians and Reptiles of Sonora, Mexico. ECO Herpetological Publishing and Distribution, Rodeo, NM.

Stebbins, R.C., and S.M. McGinnis. 2012. Field Guide to Amphibians and Reptiles of California. California Natural History Guides, University of California Press, Berkeley.

Author: Jim Rorabaugh

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