1/6 VIPERIDAE: GENERAL NOTES Adders, Vipers and Pitvipers Rattlesnake, Eastern Diamondback Cottonmouth Crotalus adamanteus Agkistrodon piscivorous PHYLUM / SUBPHYLUM Chordata / Vertebrata CLASS Reptilia ORDER / SUBORDER Serpentes / Squamata FAMILY Viperidae GENUS / SPECIES 36 genera, 256 species (See Chart) Well-known vipers include: adders, bushmasters, copperheads*, cottonmouths*, rattlesnakes*, pit vipers*. (*: in PZ) PZ vipers include: Broad-banded Copperhead, Northern Copperhead, Cottonmouth, Black-tailed Rattlesnake, Mexican Lance-headed Rattlesnake, Red Diamond Rattlesnake, Timber Rattlesnake, Western Diamondback Rattlesnake, Eyelash Palm Pit Viper. Family Viperidae 2/6 GEOGRAPHIC RANGE Africa, Europe, Asia, North America, Central America, South America. Vipers and adders are found only in the Old World. Pit vipers inhabit both the New and Old Worlds: East and Central Asia as well as North, Central and South America. There are no viperidae in Australia. HABITAT Deserts, steppes, mountains, forests, meadows and savannas in temperate and tropical environments. TOURING HIGHLIGHTS - The word "viper" is derived from Latin “vivo”: "I live" and “pario”: "I give birth". - This family of small to large snakes is venomous with hollow fangs attached to shortened, movable maxillary bones. - The most important distinguishing characteristic in all viperids is the venom apparatus which reaches its peak of effectiveness in the viperid family: i.e., retractable fangs that transmit venom much like a hypodermic needle. Their poison fangs are not grooved; they actually have enclosed canals within the fangs that transmit venom out of the body, very much like a hypodermic needle. The two upper jawbones (maxillae) which bear the fangs are very short. Each maxilla has a special joint that permits this bone, along with the fang anchored firmly within it, to rotate 90 degrees. When the viper closes its mouth, the fangs lay back, tip inward and are covered by a fold in the mucous membrane. When the mouth is opened, up to 180 degrees, a lifting mechanism is activated, putting the fangs into a vertical position to bite and inject venom. The fangs (or, more precisely, the maxillae) are laid back with the same action as when a pocket knife is snapped together. The adaptation of folding back the fangs (referred to as solenoglyphous dentition) permits them to be extremely long, far exceeding the length of those in such snakes as cobras which bear fangs that are fixed in the down, or vertical, position. The long fangs enable vipers to bite deeply into the tissues and cause the victim to suffer severe necrosis. The fangs fold back into the mouth after they are withdrawn from the victim. - Viper venom contains primarily hemotoxic material – i.e., substances injurious to the blood and the blood vessels. Thus, a viper bite typically has a very different effect from a cobra or mamba bite since their venom is primarily neurotoxic - i.e., injurious to the nervous system. Viper bites produce severe damage at the bite site and are accompanied by prominent local irritation and symptoms of severe blood poisoning, with burning pain, inflamed swellings, pronounced discoloration, sudden drop in blood pressure, internal bleeding, and degeneration of the tissues and the formation of an abscess. Some vipers, whose venom contains neurotoxic as well as hemotoxic substances, are especially dangerous – e.g., the Gaboon Viper. Bites from viperids are problems at the local level, the majority occurring in Asia, with India having the highest number. - One of the most well-known and interesting features of pitvipers (subfamily Crotalinae) is the rattle which is unique to the genera Crotalus and Sistrurus. A neonatal rattlesnake has a keratinized “button” at the tip of its tail; each time the snake sheds, a rattle segment is added. Segments of the rattle fit loosely together so that a clearly audible sound is produced when the tail is vibrated. Interspecific variation in rattle size has considerable effect on the sound, with large species producing particularly loud and effective warnings. Because most rattlesnakes shed more than once a year and because the end of rattles tend to break off in wild snakes, the number of rattle segments cannot be used as a direct indication of age. Family Viperidae 3/6 - Pit vipers are more advanced evolutionarily than vipers due to the presence of a heat- sensitive organ located between their eyes and nostrils which detect infrared rays. The nerves carry the signal to the visual part of the brain and a thermal image is created and superimposed on the visual picture, thereby allowing the snakes to appraise an invading threat. - Many species are useful for controlling rodent pests. - The European Adder, Vipera berus , is found as far north as the Arctic Circle and can tolerate the coldest climate of any snake species. The fact that the European Adder is a live bearer is an adaptation to life in a cold climate. SURVIVAL STATUS AND / OR CONSERVATION - IUCN: Critically endangered, 7 species; Endangered, 4 species; Vulnerable: 7 species; Data Deficient: 1 species. - CITES: I, 2 species; CITES II, 1 species; CITES III, 1 viperine species, 7 crotalinae species. - Details of the natural history of most viperids are not well known and the number of species listed by the IUCN and by CITES probably represents a serious underestimate of the conservation problems of this family. - Threat: habitat destruction, intentional human persecution, limited distribution ranges and vulnerability to local disturbances. - Threat, New World: rattlesnake populations are being threatened by the popularity of annual rattlesnake roundups. - Threat, Old World: viperids are hunted for use in traditional medicine. ENEMIES AND / OR DEFENSE - Enemies: raptors, other snakes, humans. - Defense, passive: camouflage (cryptic coloration). - Defense/threat, active. Some vipers inflate their bodies into sausage shapes when they are excited. Almost all vipers also can assume a plate-shaped coiled position as a threat gesture in which they lift up their necks and hold them in an S-shape. Other threat behaviors include loud hissing and rapid forward jerks of the head. Some sand dwellers hiss, strike and assume a figure 8 position and create a particularly impressive sound, akin to that of a saw cutting wood, by rubbing their lateral scales together. Many species of pitvipers vibrate their tails when disturbed and the evolution of the rattle resulted in amplification of the sound produced by this behavior. Several pitviper species give a silent, but effective, warning by gaping to reveal the bright white lining of their mouths. PHYSICAL - Configuration: vipers and adders, generally compact and sturdy; pitvipers, great variety of shape, although, in general, relatively stout with some arboreal species being more slender. - Size: small to large, ranging in length from 1’ (Dwarf Puff Adder), 5.9’ (Gaboon Adder) up to 12’ (Bushmaster). - Color: usually drab. In the vipers and adders, color can often include a dark zigzag pattern or a rhomboid band along the back; desert species are sand yellow; jungle vipers often show a colorful carpet marking. Pitvipers exhibit a great variety of shape and color for cryptic blending into their diversity of habitats. - Scales: with few exceptions, viperids have small scales on their heads, a reduction in size to facilitate skull movement as an adaptation for eating bulky prey. Dorsal scales: smooth, Family Viperidae 4/6 ridged (keeled) or granular. Ventral scales: wide smooth plates. Generally all viperids have heavily keeled body scales. The scales are not smooth; instead each scale has a slight ridge running down the centre of the scale which gives these snakes a rough appearance rather than the smooth almost "glossy" look associated with most colubrids and elapids. - Head: roughly triangular and distinct from the rest of the body. Plates may be symmetrical, fragmented or numerous and small. - Heat-sensitive pits (pitvipers only): deep, one on each side of the head between the eyes and the nostrils. Pit vipers have a unique heat-sensitive organ in the region of the face between the eyes and the nostrils which can sense infrared heat rays with temperature changes less than .001 centigrade and can distinguish not only direction, but distances of up to 2’. This capability is used primarily to appraise a predator and decide whether to stand ground or escape and, certainly, also used to catch prey. - Face: all the bones are movable. - Eyes: pupils are usually vertical and elliptical. Night adders: round. - Jaws: shortened, movable maxillary bones. - Fangs: each of the two shortened, retractile upper jawbones (maxillae) bears only the tubular venom fang (which can be activated only for a short period of time) and often 1 to several significantly smaller reserve teeth of various sizes, none being a firmly positioned poison fang. The left and right fangs can be rotated together or independently. See Touring Highlights. - Dentition: hollow, movable front fangs. Fangs are replaced throughout life. - Tail: short, but varying from quite short in rattlesnakes to relatively long in most arboreal species. The tail is prehensile in species that are adapted fully to an arboreal existence. - Copulatory organ: forked in males. LONGEVITY - In wild: range 12-25 years, varying with the species. - In captivity: 12-25 years, varying with the species. ACTIVITY PERIOD - They are typically nocturnal, but their activity periods vary with the species and seasonal conditions. DIET AND FEEDING - In wild: small vertebrates, particularly rats, mice and lizards and less often frogs and birds; invertebrate prey include locusts. - In zoo: rodents. - They paralyze or kill their prey by biting it. Viperids swallow prey that is larger relative to their body size than do non-viperids – e.g., as large as 36.4% of body mass compared to 18.4% in non-viperids. - Many viperids are ambushers and generally lie in wait for their prey, sitting quietly in one spot for long periods of time. The most specialized ambushers may feed quite infrequently.