Python (snake) - biology.

Python (snake) - biology. I INTRODUCTION Python (snake), common name for a group of nonvenomous snakes that kill by squeezing prey. Pythons mainly eat reptiles and mammals. The biggest species of pythons reach gigantic size and are capable of killing and swallowing animals as large as crocodiles, pigs, antelopes, or small deer. Pythons have rarely killed humans. Scientists have recognized at least eight genera and 32 species of pythons. The snakes are found in tropical regions of Africa, Asia, and Australia. The name python comes from a mythical giant serpent in Greek mythology. II HABITAT AND RANGE Pythons live in a wide variety of tropical and subtropical habitats, ranging from rain forests and woodlands to savannas and deserts. Some species are basically aquatic while others spend most of their time in trees. Giant species typically live on the ground but can swim or climb trees when needed. Pythons range through much of sub-Saharan Africa and through parts of southern Asia, including India, Pakistan, Nepal, Bhutan, Bangladesh, and Sri Lanka; southeastern Asia, including Thailand, Myanmar (Burma), Cambodia, and Vietnam; and in regions of southern China. They are also found in Indonesia, Malaysia, the Philippines, New Guinea, and Australia. III PHYSICAL DESCRIPTION AND BEHAVIOR Pythons are primitive snakes that, like their close relatives the boas, still show signs of lizard ancestry. Pythons have traces of a pelvis and two tiny spurlike hind limbs, usually better developed in the male. They also have two functioning lungs, one large and one small--more advanced snakes have only a single lung. Pythons lay eggs--unlike most boas, which give birth to live young. Female pythons produce from 10 to 100 eggs, depending on the species, and wrap their bodies around their clutch (group of eggs) to keep it warm and defend it against predators. Pythons can even raise their body temperature by rhythmically twitching ("shivering") their muscles to generate heat to help incubate the eggs. Incubation can last from two to three months. Baby pythons fend for themselves after hatching without parental care. Pythons range from about 1 to 10 m (about 3 to 33 ft) long and can weigh up to 140 kg (about 300 lb). Female pythons tend to be larger than males. Because pythons are cold blooded, they grow relatively slowly in the wild. They may grow more quickly with sustained care in captivity. In some species males can reach sexual maturity in 18 months and females in four years. Depending on the species, pythons can live 20 or 30 years in captivity, and in some rare cases exceed 40 years. The snakes have shorter life spans in the wild. Some species have as many as 400 sets of ribs. Their jaws can have up to 200 backward curving teeth, designed to grip prey and prevent it from pulling away. Pythons also have teeth on the roof of the mouth. Many of the bones in a python's skull are loosely attached with ligaments or skin, allowing the snake to stretch and expand the shape of its head and jaws to aid in swallowing large prey. The lower jaws can unhinge from the upper jaws and the lower jaws can spread wide apart, giving pythons a huge gape. Many pythons have striking skin patterns that help the snakes blend in with their surroundings and hide from potential prey or from predators. Blotches, spots, bands, or rings may resemble leaves, rocks, or ground cover, dappled with shadows. Some species have iridescent colors while others lack skin patterns. A few species can even shift their skin colors. Most pythons change color as they grow from juveniles to mature adults. The reticulated python of Southeast Asia is among the largest snakes, reaching a length of 10 m (33 ft). Other well-known pythons are the 6.7-m (22-ft) Indian python, a favorite of snake handlers; a subspecies of the Indian python, the Burmese python, which can reach similar size; the 9.8-m (32-ft) African rock python; and the 1.5m (5-ft) ball, or royal, python of equatorial Africa, which coils into a ball when molested. Other types of pythons include the 2-m (7-ft) green tree python, the 2.4-m (8ft) diamond python, and the 3-m (10-ft) carpet python, all found in Australia and New Guinea. IV HUNTING AND DIET Pythons mainly ambush prey, using their forked tongues to detect odors. The tongue flicks in and out to collect airborne chemicals and passes over a special smelling organ, called Jacobson's organ, in the roof of the mouth. Like most snakes, pythons have relatively poor eyesight and limited hearing. They can sense some sounds and other vibrations through the ground. A special feature found in both pythons and boas is a group of heat-sensing organs in small pits along the upper lip that allow such snakes to "see" warm-blooded animals even in dark conditions. Small pythons commonly prey on lizards while larger types of pythons typically eat mammals, reptiles, and more rarely birds. Some pythons catch fish. Pythons kill by constriction, using a powerful muscular body to squeeze a victim to death. It was once thought that pythons and other constricting snakes primarily killed by suffocating prey, gradually tightening their grip to prevent an animal from breathing. Recent research, however, shows that the enormous pressure created by the coils of such snakes can also stop circulation and even stop the heart, quickly cutting off the blood supply to the victim's brain. In addition, the force of the coils can snap an animal's neck or spine. Constriction may also break other bones, making the prey easier to swallow. Pythons typically swallow their meals starting with the victim's head. The snakes move their own flexible head and jaws over the dead prey, alternately embedding and detaching their curved teeth on each side to "walk" themselves forward over the prey and pass it into their stomachs. If disturbed or stressed, pythons can regurgitate a meal before it has been digested. The python's powerful digestive juices can break down bones, horns, and teeth as well as hide and flesh. It may take a python days or even weeks to completely digest a large meal, leaving the snake potentially vulnerable because of the bulky bulge in its body. The snake may not need to eat again for months. Pythons can temporarily increase the size of their hearts to improve the blood supply needed in digestion. However, the snake's ability to digest can be affected by warmer or cooler external temperatures, which can raise or lower the snake's metabolism. If the digestive process is too slow or the meal too large, the dead victim may begin to decay inside the snake, causing blood poisoning, or in rare cases releasing gases that can cause the snake to burst open. In addition to hunting small-to-medium-sized plant-eating mammals such as antelope, goats, deer, or wallabies, giant pythons will sometimes attack and try to eat other predators. Documented victims include crocodiles, leopards, sun bears, and even young tigers. There are also authenticated cases of pythons attacking and sometimes killing humans. However, humans are apparently difficult for pythons to swallow headfirst because of the width of the shoulders. The snake cannot easily stretch its jaws far enough side to side to consume the shoulders of a human victim. Nonetheless, pythons have reportedly swallowed human victims on occasion. Adult giant pythons have few natural enemies on land other than humans. Large crocodilians sometimes attack and eat adult pythons in water, however. Young or small pythons are prey for monitor lizards, crocodiles, storks, eagles, and predatory mammals ranging from hyenas to leopards and other cats depending on the region. V PYTHONS AND HUMANS Modern humans have lived alongside pythons for thousands of years. The giant species have been treated with both reverence and fear. Pythons have been widely associated with fertility, water, and the Earth. Some African tribes have worshiped pythons as protective spirits. Among Aboriginal Australians the Rainbow Serpent is associated with the water python. In Hinduism, the demon Agha took the form of a python to attack the god Vishnu. The World Conservation Union (also known as IUCN) and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) list all species of pythons as vulnerable and one subspecies of the Indian python as endangered. Python skins are exported from parts of Asia and Africa, mainly from animals killed in the wild. Pythons are also eaten as food in some areas. Some local populations routinely kill wild pythons out of fear. Pythons have become popular in the United States as exotic pets, including large species such as the Burmese python. Tens of thousands of Burmese pythons have been imported into the United States and sold to private owners. Captive breeding of pythons for the pet trade generates millions of dollars in the United States and Europe. The colorful and unusual skin patterns and generally docile nature of some species are seen as attractive qualities. Even a relatively small python is a powerful animal, however, and pet pythons occasionally strangle people if the snakes are mishandled or stressed. Any python over 3 m (10 ft) long needs at least two people for safe handling. In recent years, some pet owners have set large Burmese pythons free in the Florida Everglades, creating a major concern for conservationists and for rangers in Everglades National Park. Feral pythons adapt well to the near tropical conditions and have bred in the park. The pythons add a new nonnative top predator to the wildlife in the region. They are also a possible danger to unwary humans. Dozens of pythons are now captured and removed from the park in an average year. In one widely reported incident in 2005, a 4-m (13-ft) python in the Everglades burst and died after eating a 2-m (6-ft) alligator, possibly because the hefty meal began to decay before the snake could digest it. Scientific classification: Pythons make up the family Pythonidae. The reticulated python is classified as Python reticulatus, the Indian python as Python molurus, the African rock python as Python sebae, and the ball python as Python regius. The green tree python is classified as Morelia viridis, the black python as Morelia boeleni, and the carpet python as Morelia spilota. The ringed python is classified as Bothrochilus boa and the white-lipped python as Leiopython albertisii. The so-called New World python Loxocemus bicolor, found in Mexico and Central America, is not closely related to true pythons and is classified in the family Loxocemidae. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.