Description: The tiger rattlesnake is easily identified by its small, spade-shaped head, which is about 1/25 of its total body length. It has the smallest head of any rattlesnake, and a large rattle. The color pattern consists of a gray, lavender, blue-gray, pink, or buff ground color that usually turns to pink, pale orange, or cream on the sides. Tiger rattlesnakes are the only rattlesnake with crossbands on the anterior portion of their bodies, with a series of 35 to 52 gray, olive, or brown bands across the dorsum consisting mainly of heavy punctations. These crossbands have vague borders and are wider dorsally than laterally. Also mid-dorsally, the crossbands become wider than the spaces that separate them. Posteriorly, the crossbands become darker and more clearly defined. They have six to 10 posterior rings. The markings on the head are mostly vague and irregular, although towards the rear of the head, a few dark markings may be arranged as paired occipital blotches and upper temporal streaks. The most distinguishable mark on the head is a dark cheek strip. Dorsal scales are keeled and in 21 to 27 rows. A relatively small species, individuals can weigh as much as 16.0 oz. and can range in length from 18 to 36 inches, with an average length of 24 inches. Females have 164 to 177 ventral scales, and males have 158 to 172 ventral scales. Females have 16 to 21 caudal scales, and males have 23 to 27 caudal scales and are typically larger than females. They have relatively small eyes with elliptical pupils.

Habitat: Tiger rattlesnakes habitats include rocky desert canyons, foothills, and bajadas, in vegetation zones ranging from thornscrub, ocotillo-mesquite-creosote bush, saguaro-paloverde, mesquite grassland, and chaparral to tropical deciduous forest (southern Sonora) and the lower edge of oak woodland. In southeastern Arizona, this snake occurs strictly in rocky areas in winter and spring, but uses edges of arroyos in summer. It is a terrestrial species, but may climb into low vegetation.

Range: The species' range extends from central Arizona south through south-central Arizona in the United States, to southern Sonora, Mexico, including Isla Tiburón in the Gulf of California and was recently discovered in the southern Peloncillo Mountains of Arizona. The type locality is described as "Sierra Verde and Pozo Verde". The latter is a spring located on the Sonora side of the US-Mexico border, near Sasabe. This spring is on the western slope of the southern Sierra Verde, which is also known as the Sierra del Pozo Verde. In these areas, the tiger rattlesnake is observed at elevations from sea level to about 4,806 feet.

Found in these States: AZ

Venom: Although it has a comparatively low venom yield, its toxicity is considered to be the second highest of all rattlesnake venoms (next to the mojave), and the second highest of all snakes in the Western Hemisphere. It has a high neurotoxic fraction that is antigenically related to Mojave toxin (see Crotalus scutulatus, venom A), and includes another component immunologically identical to crotamine, which is a myotoxin also found in tropical rattlesnakes (see Crotalus durissus). A low but significant protease activity is in the venom, although it does not seem to have any hemolytic activity.

The average venom yield is 11 mg (dried venom) and an LD50 value of 0.6 mg/kg IP for toxicity. Other studies give LD50 values of 0.07 mg/kg IP, 0.056 mg/kg IV, and 0.21 mg/kg.

There is very little information available for bite symptoms. Human bites by the tiger rattlesnake are infrequent, and literature available on bites by this snake is scarce. The several recorded human envenomations by tiger rattlesnakes produced little local pain, swelling, or other reaction following the bite, and despite the toxicity of its venom no significant systemic symptoms. The comparatively low venom yield (6.4 to 11 mg dried venom) and short 4.0 mm (0.40 cm) to 4.6 mm (0.46 cm) fangs of the tiger rattlesnake possibly prevent severe envenoming in adult humans. However, the clinical picture could be much more serious if the person bitten was a child or a slight build individual. The early therapeutic use of antivenom is important if significant envenomation is suspected. Despite the low venom yield, a bite by this rattlesnake should be considered a life-threatening medical emergency. Untreated mortality rate is unknown but this snake has a very high venom toxicity and its bites are capable of producing major envenomation.

Diet: Tiger rattlesnakes generally feed on mammals such as rodents, but they have also been known to prey on lizards. The tiger rattlesnake ambushes much of its prey, but also actively hunts for small rodents and lizards, with juveniles relying heavily on lizards and adults depending more on rodents. In addition, these small rattlesnakes have been known to eat fairly large prey, including pocket mice, kangaroo rats, deer mice, packrats, and even spiny lizards. This species' venom is considered the most toxic of all rattlesnakes, and contains a myotoxin known to cause muscle necrosis and a neurotoxin similar to Mojave toxin. Like all pit vipers, tiger rattlesnakes inject venom into prey through long, hollow, retractable fangs. If envenomated prey crawls into a small crevice, this species is especially suited for extracting it due to its unusually small head.

Reproduction: Tiger rattlesnakes are polygynandrous, and either the male, female, or both have more than one mate within a single breeding season. Little else is known of the reproductive behavior of this species. The reproductive behavior of this species is thought to be similar to that of C. atrox and C. scutulatus. Copulation in viperids can take minutes, hours, or days, and can occur several times within a few days.

Tiger rattlesnake females follow a biennial reproductive cycle. Males follow a seasonal reproductive cycle, where sperm is stored in the vasa deferentia during winter. Breeding occurs from late May to mid-August, during the summer monsoon season. Like the majority of rattlesnakes, tiger rattlesnakes are ovoviviparous. Mean clutch size for is five young. The smallest known sexually reproducing female measured 21.3 inches snout-vent length, while the smallest mature male measured 20.2 inches.

Generally, rattlesnakes invest little in offspring following birth. However, like other viperids, female tiger rattlesnakes invest in provisioning resources for developing embryos. She eats early in the pregnancy and then finds a safe place to hide while providing the optimal thermal environment for development.

Status: Listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.

Taxonomy: