The Burmese python, Python molorus bivittarus , is native to much of Southeast Asia, including the country of Myanmar (formerly Burma). It can be found in Laos, Vietnam, Cambodia, Thailand, parts of Southern China, Northern India, and Nepal, and even across the Malacca Straits into the Indonesian archipelago.
The Burmese python is a favored pet of quite literally tens of thousands of snake fanciers in the US. Until recently, several thousand were imported into the US every year for hobbyists. Now, because the python population in its natural geographic boundaries of Asia has been threatened by overexploitation for export, many are raised within this country by the pet trade for resale to novice owners.
But the Burmese python is also a nightmare for many conservationists who fear that it will upset the balance of nature wherever else it goes.
What Makes this Snake So Popular Among Collectors?
This snake has an attractively patterned skin. Indeed, shoes and fashion accessories commonly used to be made using their skins and were a sign of affluence and high social status among wealthy urban women in the US and Europe.
The snake also allows for bragging rights among its largely male pet owners. It is one of the top ten snakes in size and weight. It can grow multiple feet in a year, and indeed it continues to grow for as long as it lives. It is by no means unusual to find year-old specimens that are several feet long that weigh in at more than 80 pounds. Adult specimens in the range of twenty feet and well over 200 pounds are not that rare in either the wild or in captivity. (The champion for size and weight appears to have been a 27 foot snake that lived in a zoo, weighing in at over 400 pounds).
While the snake is not thought to be particularly aggressive in the wild, in captivity, it tends to feed more often than other large snakes (although it can also go periods as long as a year without feeding). These instances of prey capture and devouring can provide a peculiar, if somewhat sadistic to some tastes, sort of entertainment for lovers of large snakes as pets. (The highly adaptive digestive physiology of these particular pythons is among the most studied in the world, because of its inclusion of rapid organ shrinkage and expansion, depending on the size or abundance of game or its lack.
What Makes this Python so Scary to the Rest of Us?
While not a poisonous snake, this python is a particularly effective hunter-killer. It grasps its prey with a mouth full of very sharp backward facing teeth, from which the prey can only escape by cutting itself severely during the attempt. Once the victim is trapped by these teeth, the python then whips its very muscular body around the unfortunate prey’s midsection. Once encoiled, the prey is squeezed so tight that it cannot breathe. Indeed crushed rib-cages are common among victims of a python attack. Pythons have tremendous strength, and while it is a very rare occurrence, they can kill adult humans whose size and weight approximates their own, and perhaps even humans who are a little larger than they are. The deaths of small children through python attacks are still rare, but more common.
How Have Burmese Pythons Invaded the American Wilderness?
The most plausible theory, and one borne by an abundance of anecdotal evidence, suggests that most of these invasive Burmese pythons have been released into the wild by snake fanciers who could no longer physically restrain them, or sustain the building of ever larger housing for them, once they had reached the ten foot or hundred pound weight point. They are often, with great effort, hoisted into a cage, placed in or on a car or truck, and abandoned in the brush, a local forest, or by a lake, away from their former place of captivity.
Why Don’t They Just Die from this Abandonment?
The short answer is that many do die, particularly if the surroundings are too dry (these pythons generally require a body of water nearby), too cold (pythons do not generally tolerate freezing weather, provide too little cover (pythons generally require overhanging bushes , tall grasses, or hollows in the ground and/or trees for hiding in ambush most of the day), or are without sources of food that will sustain them. (The larger they get, the less likely it is that insects and small (meaning weighing only a few ounces each) birds, amphibians, reptiles, or mammals, will sustain them. )
Survival of Individual Adults Snakes Released in the Wild
Isolated released adult pythons, particularly those that have attained larger sizes, can survive if not exactly thrive, in rather marginal climatic areas, as long as they have some of the above mentioned environmental requirements, for some times of the year. This is partly because these pythons can sometimes thermoregulate themselves so as to raise their body temperature higher than the ambient temperature, and thereby survive cold, if not persistently freezing, spells. They can also go a long time, if they have to, without eating, as long as they have had at least one good meal (something rather large animal-wise) in the last several months. Finally, there are not many predators in the United States which live in areas where the python can survive, who are large enough to kill an adult python. Bears, mountain lions, and perhaps a wolf pack could do it, but their zones of habitation, do not usually coincide with those where one would find surviving released pythons. Coyotes, foxes, hawks, eagles, and owl can manage juveniles, but not adults. But the randomly released adult pythons placed in environmentally marginal areas cannot reproduce for both reasons of both scarcity of resources, and the simple fact that there are not a lot of other pythons around with which to mate (although there are some reports of parthogeneis).
Survival of Pythons in Optimal Climates: The Everglades National Forest Story
The presence of isolated, released-by-owners Burmese pythons within the Everglades Natural Forest has been known for over 20 years, and solid proof of their successful reproduction in the wild (while long inferred from the hundreds killed in run-overs by cars and trucks ) came with the discovery of an actual breeding nest filled with a healthy clutch of eggs in 2007, by University of Florida researchers.
The Florida Everglades represents an American version of a seemingly ideal climate for Burmese pythons. It has hundreds of square miles of watery swamp, tall grasslands, a semi-tropical canopy of trees in some places, and an absolute abundance of wild game. Indeed, it is primarily because of that game (as large as adult deer, but also including a number of endangered birds and mammals) and the displacing of other predators within the food chain (including several native snakes, most of which at adulthood are less than half the size of a Burmese python) that active efforts are now being undertaken to eradicate the Burmese python as an unwelcome invasive species. About the only consideration suggesting that this is an unwise move, has been the increase in number of another invasive species, the Giant African (or Gambian) rat, a seemingly ideal food source for the pythons, which would act as a control on these 8 pound monsters.
The original working hypothesis, that the abundant local alligator population, or its less common coastal analogue, the American crocodile, (or perhaps the rarer still Florida panther) would simply control the python population by attacking and eating it, has proven to be false.
In fact, just the opposite has occurred, and there are increasing report of pythons eating the alligators and crocodiles.
A National Geographic report noted that when a thirteen foot python killed and subsequently swallowed a six foot alligator, the snake’s belly burst, so there is probably an upper limit on the size of adult alligators that can be taken. Nonetheless, it is entirely possible for pythons to reduce the number of alligators and crocodiles by preferentially preying on their young. Alligators and crocodiles guard their nests, and females initially do escort their juveniles to water, but will guard them for only a short time. They become fair game for the pythons at that point.
How Far Will They Spread in America?
Two papers from two different research groups published in the last year have quite diverging viewpoints on the potential range of Burmese pythons in America.
The first to be published was authored by the team of Gordon Rodda, Catherine Jarnevich, and Robert Reed. They work in the Invasive Species Branch of the Fort Collins Science Center, a unit of the US . Geological Survey. They basically asked themselves: What areas of the US have the right cluster of average temperature and precipitation (and thereby rivers and lakes) that would support reproducing colonies of Burmese pythons?
Their answer was startling. They suggest that coastal areas from Delaware, southwards on the east coast, and from Oregon down to California on the west coast were clearly possible places for reproducing populations, based on releases to the wild, and that much of non-coastal Texas, Oklahoma, Arkansas, Louisiana, Mississippi, Alabama, Georgia and the Carolinas, was similarly favorable.
They furthered postulated that under global warming in coming decades, as temperature rose even in the northern states, parts of Washington state, Colorado, Illinois, Indiana, Ohio, West Virginia, Pennsylvania, and even New Jersey and New York might prove hospitable.
But an exactly opposite scenario is being put forward in a later publication by a team from Biology Departments at the City University of New York and the College of Staten Island. Professors R. Alexander Pyron, Frank T. Bubrink and Timothy Guiher, suggest that the climate models used by the US Geological Survey team were faulty in that they relied on average values for temperature, precipitation, and the like. The New Yorkers basically say that these averages do not account for extremes (such as prolonged cold snaps or droughts) that could kill off significant number of pythons, and prevent those colonies from ever becoming self-sustaining.
The New York team suggests that mapping the ideal microenvironments or ecological niches, where the python-killing extremes are rarely found is the better way to go. The resulting model, which also includes a global warming component, shows that Southern Florida (where released pythons are already thriving) and Southern Texas (where few released pythons have been found, with none of them found to be breeding), are about the only places within the continental US that would prove to be reliably optimal for the pythons.
The arguments of both papers have strengths and weaknesses. The New York team basically assumes that the natural spread of Burmese pythons from their stronghold in Florida will be stopped by highly unfavorable dry zones that would have to be traversed by the snakes themselves. This presupposes that those places never have flooding rains; a situation ideal for Burmese python dispersal, owing to the fact they are excellent swimmers. They also deride the idea that released pythons elsewhere are likely to become progenitors of viable reproducing colonies, because they say such releases are likely to have already happened time and again by irresponsible owners in other parts of the country, to no avail. They suggest that this lack of success on the part of these released pythons is because only those two named spots within the US reliably provide the necessary ecological niche. In other words, releasing snakes just anywhere is not going to cause them to thrive, because, on average, the conditions are right. They have to be right virtually all the time.
But the US Geological Survey team can counter that their own method of using average values for temperature and precipitation does a very good job of predicting the areas of Asia where the Burmese python in fact, does thrive. Furthermore, their model takes into account better the python’s remarkable thermoregulatory capacity (including its use in incubating of its eggs), a factor that would enable it to expand northwards despite adverse temperature clines.
Which team is right is a matter for debate, one that may prove well worth watching, particularly if you’re afraid of say, 15 foot-long snakes weighing over 150 pounds showing up at your poolside.
Tony Stankus, FSLA, Professor, Life Sciences Librarian & Science Coordinator
University of Arkansas Libraries MULN 223 E
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I like your post. You are right that the population of Python within its natural limits of geographical Asia was threatened by over exploitation for export, many raised in this country by the PET-commerce for resale for inexperienced owners.
Posted by: רופא שיניים | July 13, 2011 at 11:42 PM