Mohave Rattlesnake – Tucson Herpetological Society

[vc_row][vc_column][vc_column_text]

Mohave Rattlesnake (Crotalus scutulatus)

[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column][/vc_row][vc_row][vc_column width=”1/2″][vc_single_image image=”2149″ img_size=”large” alignment=”center” style=”vc_box_rounded”][vc_column_text]Mohave Rattlesnake, Sulphur Springs Valley, 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=”2687″ img_size=”medium” alignment=”center” onclick=”img_link_large”][vc_column_text]Photo by Dan Bell[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][vc_column_inner width=”1/2″][vc_single_image image=”2688″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Mohave Rattlesnake, Cochise 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=”2689″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Diagnostic scalation atop the head of a Mohave Rattlesnake. 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=”2690″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Mohave Rattlesnake eating Merriam’s K-Rat, Sauceda Mtns, AZ. Photo by Sue Rutman[/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=”2691″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Mohave Rattlesnake, Photo by Young Cage[/vc_column_text][/vc_column_inner][vc_column_inner width=”1/2″][vc_single_image image=”2692″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Mohave Rattlesnake, Photo by Young Cage[/vc_column_text][/vc_column_inner][/vc_row_inner][vc_row_inner][vc_column_inner width=”1/2″][vc_single_image image=”2693″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Mohave Rattlesnake, Photo by Young Cage[/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 Mohave Rattlesnake (Crotalus scutulatus) is a large (< 1290 mm total length [Stebbins and McGinnis 2012], but most are < 1000 mm), heavy-bodied snake with a heat-sensing pit between the eye and the nostril and prominent rattles on the tail. The head is broad and triangular, and the pupil is vertically elliptical. The dorsal ground color is gray, greenish-gray, yellowish-gray or brown with 27-44 light-bordered, dark diamonds or blotches. The tail has 2-8 dark bands on a light gray background. The dark tail bands are narrower than the lighter interspaces, and those interspaces are usually distinctly lighter than the ground color on the body. Dorsal scales are keeled, in 25 (21-29) rows at mid-body, and are not individually speckled. Two (sometimes 3 and very rarely 4) relatively large scales are situated between the supraoculars anteriorly (see image gallery). A light stripe that begins just behind the eye angles downward to in back of the corner of the mouth. Two subspecies are recognized. Only C. s. scutulatus occurs in our area. We follow (Crother 2017) in regard to the common name, but Jones (2016) suggests “Mojave Rattlesnake” is more appropriate (but see Cardwell 2016).

In the 100-Mile Circle, the Mohave Rattlesnake is most commonly confused with the Western Diamond-backed Rattlesnake. In that species, the dark and light tail bands are of nearly equal width and strongly contrast with each other, the dorsal scales are peppered with dark speckling, 3-8 small scales lie between the supraocular scales, and the light stripe that angles from just in back of the eye and downward ends in front of the corner of the mouth. The Western Diamond-backed Rattlesnake also grows to a larger size (<1676 mm total length in Arizona). Mohave Rattlesnakes in southeastern Cochise County are sometimes mistaken for Prairie Rattlesnakes (Crotalus viridis), but that species is not known from southern Arizona, it has more than two internasals in contact with the rostral (two in the Mohave Rattlesnake – see image gallery), banding on the tail is less distinct, and the dorsal blotches are more irregularly oval (elongated into crossbands on the posterior of the body) than diamond-shaped.

The Mohave Rattlesnake is broadly distributed within the 100-Mile Circle where Sonoran and Chihuahuan desertscrub, semi-desert grassland, and Plains grassland occur at elevations of about 320-1560 m. It likely occurs sparingly into oak savanna in the San Rafael Valley and perhaps elsewhere. Cardwell (2016) reports it from pine-oak woodland but does not provide specific localities. Typically a snake of flats and lower bajadas, it occasionally follows drainages or mesas into foothills or lower mountains. In the eastern portions of the Circle, the local distribution of the Mohave Rattlesnake often tracks that of the grasslands, whereas in adjacent Chihuahuan desertscrub the Western Diamond-backed Rattlesnake is more abundant or replaces the Mohave Rattlesnake.

Based on road-riding records from Highway 80 and the Portal Road in southeastern Cochise County, Mendelson and Jennings (1992) surmised that Mohave Rattlesnakes had declined and Western Diamond-backed Rattlesnakes had increased as a result of a transition of vegetation communities from semi-desert grasslands to Chihuahuan desertscrub during the period 1959-1961 to 1987-1989. The latter species is also more apt to be found in rugged terrain. In the western portions of the Circle, the habitat partitioning of Mohave and Western Diamond-backed Rattlesnakes is harder to define and more subtle, but the latter predominates in more dissected bajadas or where there are large rocks or boulders, whereas the Mohave Rattlesnake is more a species of valleys and gentle bajadas. Furthermore, throughout the 100-Mile Circle, the Western Diamond-backed Rattlesnake far outnumbers the Mohave Rattlesnake in river bottomlands, such as along the San Pedro and Gila rivers.

The Mohave Rattlesnake is often fairly abundant. On Highway 80 and the Portal Road, it was the most abundant snake during 1987 and 1989 (Mendelson and Jennings 1992). It was the second most common snake on roads west and south of Phoenix (Jones et al. 2011). It is less common in the western deserts of Arizona. During 1987-1991 at Organ Pipe Cactus National Monument, the Mohave Rattlesnake was the seventh most abundant snake observed on Highway 85 (Rosen and Lowe 1996).

The Mohave Rattlesnake is terrestrial and not a particularly good climber. It is primarily nocturnal at lower elevations in summer, but considerable activity occurs in the morning or late afternoon in spring and fall, as well as during the summer at higher elevations. It has been collected from mid-February to late November in the Circle, but most are found from April through September. Mohave Rattlesnakes are infrequently seen basking on warm winter days.

Mating occurs in spring and then again in late summer. Females give birth to litters of 2-17 (mean = 8.2) young in July through September. Neonates are 264-278 mm SVL and frequently are seen in August and early September in southern Arizona. Mammals are the most common prey, including various rodents, ground squirrels, cottontail rabbits, and jackrabbits. However, birds, bird eggs, lizards, a snake, toads, spadefoots, frogs, insects, centipedes, millipedes, and carrion have also been reported in the diet. Young Mohave Rattlesnakes likely consume fewer mammals than adults.

It is often suggested that Mohave Rattlesnakes are more dangerous than other species, primarily because of the venom produced by most populations which has been shown repeatedly to be more deadly to laboratory mice than the venom of other rattlesnakes (e.g. Glenn and Straight 1978). Yet, while Mohave Rattlesnakes are common animals and responsible for many bites, deaths in people are rare (Hardy 1983, 1988; Massey et al. 2012).

Lethality in mouse studies is due to a potent neurotoxin in their venom throughout most of their range – which extends south and east from California through western and southern Arizona and deep into mainland Mexico. However, the Mohave Rattlesnakes in southcentral Arizona – an area roughly defined by eastern Maricopa County, most of Pinal County, Gila County (south of the Mogollon Rim) and northeastern Pima County – produce a more typical rattlesnake venom, full of tissue-destroying enzymes but lacking the neurotoxin. A few animals around the edge of this region produce both neurotoxin and tissue-destroying toxins.

But most Mohave Rattlesnakes with neurotoxic venom lack the tissue-destroying enzymes. As a result, their bites often fail to produce the localized swelling and bruising usually associated with rattlesnake bites and the neurotoxic effects may not appear for hours. Bites by any rattlesnake, whether a Mohave or another species, are medical emergencies and immediate medical attention must be sought, even if no initial effects are apparent.

The Mohave Rattlesnake is listed as a species of least concern on the IUCN’s 2015 Red List. However, it is eliminated by urban and agricultural development, and a long-term trend of desertification of grasslands in southeastern Arizona is adversely affecting this species. With a valid Arizona hunting license, four Mohave Rattlesnakes may be taken per year or held in possession, alive or dead, except that take of these snakes is prohibited without special authorization in protected areas such as Saguaro National Park and National Wildlife Refuges.

Mohave Rattlesnake (Crotalus scutulatus)

Description

DONATE TODAY

THANK YOU FOR YOUR SUPPORT

Search the Site

CONTACT THS

Archive