outcroppings, and tend to avoid coarse sand. Occasionally they are found around oases, and up to an altitude of . Cooler temperatures, with annual averages of or less, are preferred. Behavior They typically move by sidewinding, during which they press their weight into the sand or soil, leaving whole-body impressions. Often, it is even possible to use these impressions to make ventral scale counts. They have a reasonably placid temperament, but if threatened, they may assume a C-shaped posture and rapidly rub their coils together. Because they have strongly keeled scales, this rubbing produces a rasping noise, similar to the sound produced by snakes of the genus Echis. In the wild, they are typically ambush predators, lying submerged in sand adjacent to rocks or under vegetation. When approached, they strike very rapidly, holding on to the captured prey (small birds and rodents) until the venom takes effect. Reproduction In captivity, mating was observed in April and always occurred while the animals were buried in the sand. This species is oviparous, laying 8–23 eggs that hatch after 50 to 80 days of incubation. The eggs are laid under rocks and in abandoned rodent burrows. The hatchlings measure 12–15 cm (about 5–6 inches) in total length. Venom Cerastes cerastes venom is reported to be similar in action to Echis venom. Envenomation usually causes swelling, haemorrhage, necrosis, nausea, vomiting, and haematuria. A high phospholipase A2 content may cause cardiotoxicity and myotoxicity. Studies of venom from both C. cerastes and C. vipera list a total of eight venom fractions, the most powerful of which has haemorrhagic activity. Venom yields vary, with ranges of 19–27 mg to 100 mg of dried venom being reported. For venom toxicity, Brown (1973) gives values of 0.4 mg/kg IV and 3.0 mg/kg SC. An estimated lethal dose for humans is 40–50 mg. Taxonomy A number of subspecies have been described: Cerastes ceraste hoofieni Werner & Sivan, 1999 – Saudi Arabia. Cerastes ceraste karlhartli Sochurek, 1974 – Egyptian horned viper – southeast Egypt and Sinai Peninsula. Cerastes ceraste mutila Domergue, 1901 – Algerian horned viper – southwest Algeria, Morocco. Previously, C. gasperettii was also regarded as a subspecies of C. cerastes. References Further reading Boulenger GA. 1896. Catalogue of the Snakes in the British Museum (Natural History). Volume III., Containing the...Viperidæ. London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). xiv + 727 pp. + Plates I.-