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snakes, serpents, asps
Over 15 families
Over 3,000 species
Long, scale-covered vertebrates with limbless bodies. They also lack eyelids and external ear openings. Along the underside of the body, snakes have a specialized row of scales. Some families of snake retain vestigial pelvic girdles although none have pectoral girdles. The bones of the upper jaw are not fused at the snout, but can "unhinge".
Ranges from 13 cm (5 inches) to over 11 m (36 ft) in length
Varies per individual and length; ranges from 1 g (0.002 lb.) to over 226.8 kg (500 lbs.)
All snakes are predators. Many species have highly specialized diets. Some burrow into soil and feed on worms and insects while others exclusively seek out eggs or snails. Snakes also may prey on fishes, birds, small mammals, amphibians, large invertebrates, and even other reptiles, including other snakes.
Depends on species - may be oviparous (egg laying), viviparous (live bearing) or ovoviviparous ("egg live birth").
Varies by species
10-40 years, depending on size
Snakes are found throughout the tropical and temperate regions of the world on every continent, save Antarctica. They are most abundant in the tropics.
Snakes inhabit a vast range of environments, including temperate forests, tropical jungles, grasslands, deserts, swamps, and oceans. Essentially, the only habitats in which they are not found are regions of excessive and pervasive cold (i.e. polar regions).
Many species listed
Many species listed
Several species listed as threatened and one species as endangered
A snake's skull is flexible in that the individual bones are able to move away from each other. Elastic ligaments connect the bones to each other. The joint between the upper and lower jaw enables the snake to open their jaws as widely as possible. The two halves of the lower jaw are also connected by ligaments, which enable the pieces to move independently of one another. Such adaptations are necessary for feeding on prey that is larger than their head.
Snake's teeth are not used to chew their food. The prey, whether killed or still alive, is always swallowed whole. Therefore, the skull must be able to withstand an incredible amount of stress considering snakes are able to take in prey that is 2 to 4 times the width of their head.
Snakes have powerful digestive enzymes that can break down tough materials like feathers, hair, and bone. Some species inject saliva containing venomous enzymes into their prey. The saliva is injected through teeth called fangs. The venom causes tissue damage and begins the digestive process. Sometimes this venom can be quite dangerous in species like cobras, rattlesnakes, kraits, vipers, and sea snakes. There are approximately 300 snake species that are considered extremely dangerous to humans, although toxic elements can be found in the saliva of many species considered nonvenomous.
Another feeding tactic used by snakes is constriction. A constrictor loops its body around prey and exerts pressure on its victim from two or more points as the prey exhales. The constricted animal is prevented from inhaling; death comes from suffocation. Many of the largest snakes, such as the anaconda (Eunectes murinus), are constrictors. Anacondas can reach lengths of more than 7.6 m (25 ft.) and consume birds and small mammals including deer and tropical pigs called peccaries. One large specimen was found to have a 1.8 m (6 ft.) caiman (a type of crocodilian) in its stomach.
Lacking external ear openings, hearing in snakes is geared for sensing vibrations. Their eyesight is basically poor, sensitive only to movement. Snakes usually find prey with their advanced sense of smell. Snakes have a specialized organ called the Jacobson's Organ, which consists of two pits lined with a sensory tissue. When snakes flick their tongue, tiny particles of scent are transported to the pits of Jacobson's Organ, which then tells the snake all about its prey.
Pit vipers have facial pits found below and between the eye and nostril on both sides of the head. The pit is highly sensitive to infrared radiation (heat) and serves as a direction finder in locating warm-blooded prey or predators.
The rattlesnake's rattle is a series of hard segments made of keratin. A new segment is added each time a snake sheds. When shaken, the segments vibrate against each other, producing a familiar buzz.
ECOLOGY AND CONSERVATION
In their role as predators, snakes help keep small animal, especially rodent, populations in check. Snakes are often hunted for their meat and skin, but mainly they are threatened by loss of habitat and out of human fear.
Ashton, Ray Jr. and Patricia Sawyer Ashton.
Reptiles and Amphibians of Florida: Part One, The Snakes
. Miami. Windward Pub., 1988.
Mehrtens, John M.
Living Snakes of the World
. New York. Sterling Publishing Co., Inc. 1987.