Rock Rattlesnake – Tucson Herpetological Society

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Rock Rattlesnake (Crotalus lepidus)

[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column][/vc_row][vc_row][vc_column width=”1/2″][vc_single_image image=”2153″ img_size=”large” alignment=”center” style=”vc_box_rounded”][vc_column_text]Rock Rattlesnake, Huachuca Mtns, 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=”2711″ img_size=”medium” alignment=”center” onclick=”img_link_large”][vc_column_text]Photo by Young Cage[/vc_column_text][gap size=”12px” id=”” class=”” style=””][/vc_column_inner][vc_column_inner width=”1/2″][vc_single_image image=”2712″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Photo by Young Cage[/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=”2713″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Female Rock Rattlesnake with young, Chiricahua Mtns, 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=”2714″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Small juvenile Rock Rattlesnake, Huachuca Mtns, AZ. Photo by Larry Jones[/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=”2715″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Male Banded Rock Rattlesnake, Animas Mtns, SW NM. Photo by Jim Rorabaugh[/vc_column_text][/vc_column_inner][vc_column_inner width=”1/2″][vc_single_image image=”2716″ img_size=”medium” alignment=”center” style=”vc_box_rounded” onclick=”img_link_large”][vc_column_text]Rock Rattlesnake eating Scolopendra centipede, Arizona © 2007 Manny Rubio / ASDM Sonoran Desert Digital Library[/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 Rock Rattlesnake (Crotalus lepidus) is a moderately long (< 828 mm total length, but most are < 610 mm in Arizona) and relatively robust snake, with a heat sensing pit between the eye and nostril, and prominent rattles on the tail. In our area, the dorsal pattern is gray or greenish with 13-21 narrow, dark brown or black bands on the body, and 1-6 such bands on the tail. Dark speckling or small dark spots, some of which may form incomplete bands, may be present between the primary bands. The dorsal scales are keeled and usually in 23 mid-body rows. The rostral is in contact with the anterior nasal scales, and in our area, the upper preocular scales are vertically divided. The pupils are vertically elliptical.

In the subspecies that occurs in our area (C. lepidus klauberi), sexual dimorphism is often apparent in the dorsal pattern of adults. The background color or sometimes just the mid-dorsal region of adult males tends to be greenish, whereas adult females are gray. These colors and the dorsal banding pattern may help camouflage the Rock Rattlesnake against the often gray rocks and areas of green lichen that are common in its habitat (Jacob and Altenbach 1977, but see Prival and Porter 2016). Males grow to a larger size and have longer tails as a proportion of total length than females. The neonate tail is yellow, a color that gradually fades, but at least a trace of that color is usually retained into adulthood.

Four subspecies are currently recognized (Crother 2012), including the Banded Rock Rattlesnake, C. lepidus klauberi, of southeastern Arizona, southwestern New Mexico, the mountains around El Paso, Texas, and southward across much of the Mexican Plateau to Jalisco; the Mottled Rock Rattlesnake, C. lepidus lepidus, which occurs in southeastern New Mexico and southwestern Texas south to San Luis Potosí; and two subspecies that occur exclusively in Mexico, the Durango Rock Rattlesnake, C. lepidus maculosus, and the Tamaulipan Rock Rattlesnake, C. lepidus morulus. The species occurs from southeastern Arizona, southern New Mexico, and western Texas south to southern Tamaulipas, San Luis Potosí, Aguascalientes, and northern Jalisco.

The Rock Rattlesnake is fairly distinctive and not likely to be confused with any other snake in the mountains of the 100-Mile Circle, except perhaps the Tiger Rattlesnake (Crotalus tigris), which occurs in some of the same mountains as the Rock Rattlesnake. The dorsal pattern of both species is dominated by dark crossbands; however, the Tiger Rattlesnake has more (35-52) bands on the body, the anterior bands near the neck may form blotches, and the upper preocular scale is not divided. The Tiger Rattlesnake is often a larger snake, as well (< 912 mm total length). A hybrid Rock Rattlesnake X Ridge-nosed Rattlesnake (Crotalus willardi) was found in the Peloncillo Mountains, New Mexico (Campbell et al.1989).

In Arizona, the Rock Rattlesnake has been found in the Santa Rita, Huachuca, Whetstone, Dragoon, Chiricahua, Dos Cabezas, and Peloncillo mountains, and the Canelo Hills at elevations of about 1495-2500 m. In northern Sonora, it has been found only in the Sierras Pan Duro, San Luis, Mariquita, Elenita, and la Madera (the latter is northeast of Moctezuma). It occurs from the upper edge of the semi-desert grassland upslope through oak woodland, pine-oak woodland, and marginally into mixed conifer forest. The Rock Rattlesnake, as its name implies, is most often found at or near talus slopes and rock outcrops, but may be encountered along canyon bottoms or under logs or other surface debris in the mountains. Gravid females tend to occupy warmer sites, such as open areas on south or west-facing slopes, as compared to males and non-gravid females (Prival 2008). At times during the summer rainy season and into October, this species may be frequently encountered, but at other times, particularly during the dry fore summer and spring, they may be very hard to find. Collection records in Arizona run from mid-April through December, but most are found from June into October. It can be found basking on warm winter days (McCrystal et al. 1996). The buzzing of the Rock Rattlesnake’s rattles is often heard before the snake is seen.

This is primarily a diurnal snake, with most activity during the morning into mid-afternoon, and then again in the late afternoon. These snakes are only rarely found active after dark. This is primarily a terrestrial species, but it is not uncommonly observed perched atop rock outcrops and has even been found a meter or more up into trees and shrubs. In the Chiricahua Mountains, mating was observed from mid-July to mid-August, and gravid snakes were found from late July to late August. Females apparently store sperm over winter. The smallest gravid female was 332 SVL (Prival 2008). Females have been known to give birth to 1-9 young, although Armstrong and Murphy (1979) found a female in Sinaloa surrounded by 11 young. Newborn young typically stay with their mothers for 11-14 days until their first shed is complete (Prival and Porter 2016). Neonates, which measure 160-240 mm total length, were found in the Chiricahua Mountains beginning in early August (Prival 2008).

The diet of wild Rock Rattlesnakes from our area is predominantly lizards, followed, in order of frequency, by centipedes (Scolopendra sp.), mammals, birds, and snakes. Yarrow’s Spiny Lizard (Sceloporus jarrovi) was the most common prey item. Prey items are usually swallowed head first (Holycross et al. 2002). Captives have also taken frogs and salamanders. Young Rock Rattlesnakes sometimes wave their yellow tails (caudal luring) to attract lizards.

The venom of the Rock Rattlesnake probably targets vertebrates more than invertebrates. For humans, it is highly hemorrhagic, causing swelling, bleeding, and local necrosis. The venom of some populations also contains potent neurotoxins, similar to that found in Mojave Rattlesnake venom. Although no human mortalities have been reported, any bite from a Rock Rattlesnake should be considered life threatening, and immediate medical attention should be sought. This snake can move unexpectedly fast and is quick to strike.

The Rock Rattlesnake is listed as a species of least concern on the 2015 IUCN’s Red List; however, collection and possession in Arizona is prohibited without specific authorization from the Arizona Game and Fish Department. This attractive snake is popular with poachers, and removal of snakes, as well as associated destruction or disturbance of habitat may have impacted some populations (Johnson and Mills 1982, Rubio 2010). High intensity wildfires, driven by climate change, are a growing threat, and in Sonora some montane habitats of this species have been impacted by logging.

Rock Rattlesnake (Crotalus lepidus)

Description

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