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Western Massasauga (Sistrurus tergeminus)

[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column][/vc_row][vc_row][vc_column width=”1/2″][vc_single_image image=”2157″ img_size=”large” alignment=”center” style=”vc_box_rounded”][vc_column_text]Massasauga, Cochise County, AZ. 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=”2800″ img_size=”medium” alignment=”center” onclick=”img_link_large”][vc_column_text]Western Massasaugas copulating (captives). 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=”2801″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Western Massasauga, southeastern Arizona © 2007 Manny Rubio / ASDM Sonoran Desert Digital Library[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/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

Editor’s Note:  In 2013 the International Commission on Zoological Nomenclature revised the names for Massasaugas.  Snakes west of the Mississippi River are now Sistrurus tergeminus. Recently, Beauchamp and Calvert (2015, Herp Review 46(4):176-177) documented a previously unknown population of the Western Massasauga on Ash Flat of the San Carlos Apache Reservation, Graham County, AZ.

In the United States, this beautiful rattlesnake is distributed from central New York in a broad, diagonal swathe across the Midwest to southeastern Arizona. Populations are also known from the region around Georgian Bay in Ontario, Canada and in México from Cuatro Ciénegas, Coahuila (McCoy and Minckley 1969) and Aramberri, Nuevo León (Minckley and Rinne 1972). Three subspecies are currently recognized, though only the Desert Massasauga is found in Arizona. The Eastern Massasauga (Sistrurus catenatus catenatus) and Western Massasauga (S. c. tergeminus) are found in the eastern and midwestern portions of the species range. Despite an extensive distribution, relatively few and substantially isolated populations of Massasauga are threatened by loss and degradation of habitat, road mortality, and deliberate extermination. Southwestern populations might be particularly vulnerable to further climate changes (Greene 1994).

In Arizona, anthropogenic desertification has effected dramatic reduction of an already limited distribution; only two populations are demonstrably extant. In Arizona, specimens have been taken from the San Bernardino, San Simon, San Pedro, and Sulphur Springs valleys in Cochise County. Historic vouchers suggest that Desert Massasauga were once distributed throughout the San Simon and San Bernardino valleys. However, conversion of desert grassland to desert scrub, and a lack of recent specimens, suggests this “population” is now restricted to a relictual tobosa grassland straddling the divide between these valleys. In this small patch of grassland, Desert Massasauga represented approximately 16% of all snakes (n = 667) encountered on the road, although nearly half of these were found DOR (Holycross and Douglas 1996). A relatively recent specimen (Sinclair and Snell 1990) suggests that a low-density population persists in deteriorated tobosa grassland in the southern Sulphur Springs Valley (see Rosen et al. 1996). A specimen collected by Dr. T.E. Wilcox from the “parade grounds” of Fort Huachuca in the late 1890’s suggests a population once occupied grasslands on the northern and eastern bajadas of the Huachuca Mountains. A lack of recent vouchers suggests this population is either extirpated or present at very low density. Desert Massasauga are relatively small rattlesnakes that reach a maximum of 541 mm SVL (Holycross 2002), although most adults encountered in Arizona are 300 – 400 mm SVL. Compared with many other rattlesnakes, the head is narrow and the rattle small. Dorsal ground color is typically light gray to silver near the spine, often becoming suffused with reddish brown laterally. A sharply contrasting brown mask bordered by thin white margins extends from the eyes to behind the corners of the mouth. Two blotches forming a lyre shape extend from the back of the head onto the neck. A mid-dorsal row of 33 to 40 chocolate blotches ornaments the back. The tail is yellow to orange at birth, but within a year changes to the adult form of light gray with five to 10 brown cross-bands. The belly is often uniformly light gray to light brown with darker flecking. The rattle distinguishes this snake from similarly patterned colubrids. Among the rattlesnakes, only juvenile Mojave Rattlesnakes (Crotalus scutulatus) and Prairie Rattlesnakes (Crotalus viridis) are similar in appearance and only Mojave Rattlesnakes are sympatric with Desert Massasauga in Arizona. No other rattlesnake in Arizona has nine large “plate-like” scutes on the top of the head, though Mojave Rattlesnakes have large interoculars.

Throughout its range the Massasauga occupies a broad array of habitat types. Eastern and Western Massasauga occupy wet meadows, marshes, and woodlands. In the west, Desert Massasauga are found in shortgrass prairies, desert grasslands, and even in shinnery oak shrublands in New Mexico (Degenhardt et al. 1996). In Arizona Desert Massasauga occur exclusively in desert grasslands. The San Bernardino/San Simon Valley population inhabits picturesque tobosa grassland that blankets a volcanic cinder field and most individuals are encountered on the gently sloping bajadas found around the base of large cinder cones (Holycross and Douglas 1996). Here, loose igneous rocks and wiry bunch grasses are scattered on a surface of friable, red volcanic soils. During the dry spring and early summer, radio-tracked adults often spent the day in the burrows of small rodents, and infrequently used Banner-tailed Kangaroo Rat burrows as refugia. Once the summer rains began, I often found them nestled deep in the base of tobosa clumps. In December I found two radio-tracked individuals high on a cinder cone bajada in small rodent burrows with entrances about 2 cm in diameter.

In an assessment of range-wide variation in Massasauga diet, Holycross and Mackessy (2002) identified 165 prey from populations of Desert Massasauga in Arizona, New Mexico and Colorado. Prey included 97 lizards, 51 mammals, 15 Scolopendromorph centipedes, one toad (Plains Spadefoot, Spea bombifrons), and one snake – Plains Black-headed Snake, Tantilla nigriceps). Diet was surprisingly homogeneous among these widely separated populations of Desert Massasauga, but differed dramatically from the diets of populations of Eastern and Western Massasauga. Among Desert Massasauga from Cochise County, approximately ¾ of prey were abundant diurnal lizards, including Desert Grassland Whiptails (Cnemidophorus uniparens), Eastern Fence Lizard (Sceloporus “undulates”), Lesser Earless Lizard (Holbrookia maculata), and Ornate Tree Lizard (Urosaurus ornatus). The stomach of one adult male contained one each of Desert Grassland Whiptail, Eastern Fence Lizard, and Ornate Tree Lizard! Large centipedes are regularly consumed. Fowlie (1965) reported that Desert Massasauga feed primarily on anurans based on “examination of stomach contents”, though neither specific data nor references to specimens were provided. Juvenile Massasauga have yellowish tails that they use to lure prey. Captive Eastern and Western Massasauga caudal lure for frogs (Reiserer 2002; Schuett et al.1984) but do not appear to lure for lizards. Conversely, Desert Massasauga from Arizona lure for lizards but not frogs (Reiserer 2002). Greene and Oliver (1965) report scavenging on the Hognose Snake (Heterodon nasicus).

Desert Massasauga are primarily nocturnal during the summer and are most often found moving during the hours following dusk. However, they may be discovered abroad throughout the night, for several hours after sunrise, and on overcast days in late afternoon. Increased movements and surface activity are coincident with spring egress and the advent of monsoon rains.

Goldberg and Holycross (1999) present reproductive data for Arizona and Colorado populations of Desert Massasauga. Males underwent spermatogenesis from June through October but contained sperm in the vasa deferentia and had enlarged kidney sexual segments April through October, suggesting males are capable of inseminating females throughout this period. Ernst (1992) stated that breeding extends from March through October. Although courtship and mating remain unobserved in wild Arizona populations, Lowe et al. (1986) report captives from Arizona mate in both the spring and fall. Chiszar et al. (1976) describe courtship behavior of captive S. c. tergeminus. Goldberg and Holycross (1999) report females with vitellogenic follicles or embryos from April through August and suggest births may occur from late August through late September, much later in the year than any other Arizona rattlesnake. Only 15% of adult females from Arizona and Colorado were reproductively active. Litter sizes in wild females ranged from 4-8 (5.8 ± 1.7, N = 4). Four wild neonates measured 162, 166, 167 and 176 mm SVL and weighed 3.9, 5.1, 4.9, and 3.4 g, respectively. The smallest reproductively active male measured 280 mm SVL and Desert Massasauga represented approximately 16% of all snakes (n = 667) encountered on the road, although nearly half of these were found DOR. The smallest reproductively active female was 329 mm SVL.

The Desert Massasauga is listed as a “Species of Special Concern” by the Arizona Game and Fish Department and is protected by a year-round closed hunting season.

Literature Cited

Chiszar, Scudder, Smith and Radcliffe. 1976. Observations of courtship behavior in the western massasauga (Sistrurus catenatus tergeminus). Herpetologica 32:337-338.

Degenhardt, Painter and Price. 1996. Amphibians and Reptiles of New Mexico. University of New Mexico Press, Albuquerque.

Ernst. 1992. Venomous Reptiles of North America. Smithsonian Institution Press, Washington, D. C.

Fowlie. 1965. The Snakes of Arizona. Their Derivation, Speciation, Distribution, Description, and Habits – A Study in Evolutionary Herpeto-Zoogeographic Phylogenetic Ecology. Azul Quinta Press, Fallbrook, California

Goldberg and Holycross. 1999. Reproduction in the desert massasauga, Sistrurus catenatus edwardsii, in Arizona and Colorado. Southwestern Naturalist 44:531-535.

Greene. 1994. Systematics and natural history: Foundations for understanding and conserving biodiversity. American Zoologist 34:48-56. Greene and Oliver Jr. 1965. Notes on the natural history of the western massasauga. Herpetologica 21:225-229.

Holycross and Douglas. 1996. Distribution, Abundance, and Ecology of the Desert Massasauga Rattlesnake, Sistrurus catenatus edwardsi. Arizona Game and Fish Department Heritage Report, Phoenix.

Holycross. 2002. Sistrurus catenatus edwardsii. Maximum size. Herpetological Review 33:59.

Holycross and Mackessy. 2002. Variation in the diet of Sistrurus catenatus (Massasauga), with emphasis on S. c. edwardsii (Desert Massasauga). Journal of Herpetology 36:454-464.

Lowe, Schwalbe and Johnson. 1986. The Venomous Reptiles of Arizona. Arizona Game and Fish Department, Phoenix.

McCoy and Minckley. 1969. Sistrurus catenatus (Reptilia: Crotalidae) from the Cuatro Ciénegas Basin, Coahuila, Mexico. Herpetologica 25:152-153.

Minckley and Rinne. 1972. Another massasauga from Mexico. Texas Journal of Science 23:432-433.

Reiserer. 2002. Stimulus control of caudal luring and other feeding responses: A program for research on visual perception in vipers. Pp. 361-383 in Biology of the Vipers, Schuett, Höggren, Douglas and Greene (eds.). Eagle Mountain Press, Eagle Mountain, Utah.

Rosen, Sartorius, Schwalbe, Holm and Lowe. 1996. Draft Annotated Checklist of the Amphibians and Reptiles of the Sulphur Springs Valley, Cochise County, Arizona. Arizona Game and Fish Heritage Report, Phoenix.

Schuett, Clark and Kraus. 1984. Feeding mimicry in the rattlesnake Sistrurus catenatus, with comments on the evolution of the rattle. Animal Behavior 32:625-626. Sinclair and Snell. 1990. Sistrurus catenatus edwardsii. Geographic Distribution. Herpetological Review 21:42.

Wright and Wright. 1957. Handbook of Snakes of the United States and Canada, 2 vols. Comstock Publishing Associates, Ithaca, New York.

Author: Andrew Holycross

Originally Published in Sonoran Herpetologist 2003 16(40):30-32

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