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Getting Acquainted

Michael Barron has flown helicopters over the vast horizons of Everglades National Park for years. During that time, he has piloted researchers to every remote corner of the backcountry, scoured the landscape in search of bird rookeries and alligator nests, and ferried countless firefighters to the front lines of sprawling conflagrations. And yet despite all he has seen in the wilds of south Florida, little could compare to what he encountered while hovering over the marsh one day in September of 2005.

Flying high above the northern reaches of the park with a pair of researchers on board, Barron saw an unusually shaped figure below. Deciding to investigate, he set the floats beneath his craft gingerly into the inundated sawgrass prairie. Exiting the vehicle, he sloshed a short distance through hip-deep water to find a gruesome scene. There, floating amidst emergent vegetation and open water were the decapitated remains of a nearly 13-foot Burmese python. The animal was badly bloated, and protruding from its ruptured stomach were the tail and hind quarters of what appeared to be a large alligator. Barron surveyed the scene briefly, but didn’t stay long. “I started getting a little nervous about being up to my waist in the water,” he later recounted, “in an area where there’s twelve-foot pythons hanging around.” Barron managed to snap a few quick photos before returning to his airship for the journey home (Figure 4).

The subsequent day, Barron piloted park biologist Skip Snow out to the area to examine the macabre curiosity he had found in the marsh. Upon landing, Snow set to work. Conducting a necropsy in the field, Snow determined the alligator (now in an advanced state of decay) to be over six feet in length. In the python’s intestines, he found large pieces of the alligator’s skin. Though the puzzling scene provided little to explain why the serpent perished, how its stomach ruptured, or how it lost its head, one thing seemed clear—at some point the python had managed to subdue and consume the monarch of the Everglades marsh.

Media interest flared yet again as news of the discovery spread. Snow was interviewed extensively, and Barron’s crime scene photos were published around the world. Numerous national papers detailed the story, touting banner headlines reading “Clash of the Titans” and “Fatal Indigestion.” Internationally, the gory pictures of the eviscerated serpent were bandied about by the BBC, The Sydney Morning Herald, and The Daily Telegraph. And taking a cue from America’s Most Wanted, National Geographic aired an hour-long documentary that attempted to expose details behind the fatal encounter. Using sophisticated computer animations and laboratory experiments, the episode only added to the confusion by offering a new hypothesis that implicated a second alligator in the scuffle. Despite extensive investigation, the curious double homicide would forever remain steeped in mystery. But for many viewers and readers, the resulting coverage and publicity provided their first glimpse of the Florida Everglades—one far different than the idyllic picture-perfect sunset over an open expanse of sawgrass.

In addition to providing new insight regarding the mutual relish with which alligators and pythons might consume one another, Barron’s gruesome discovery also provided an important new data point. The amazing alligator-eating python was one of the first of his ilk to be found in Shark Slough—the liquid heart of Everglades National Park. Not only were pythons now known to be capable of swallowing large alligators, but it was becoming increasingly apparent that they readily occupied the same watery haunts.

In a coincidence that mirrored a bad publicity stunt, ABC premiered Invasion, a suspense series about aliens infiltrating the Florida Everglades, that same month. The show featured sets that barely resembled the Glades, starred impossibly attractive actors playing park rangers, and followed a storyline as thin as spider’s silk. In only a year, the show’s viewership went south, but in the true Everglades it seemed real invaders were headed farther north.

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Historically, the Burmese python (Python molurus bivittatus) has long proven difficult to categorize—so much so that successive generations of taxonomists have waffled about its proper classification. For the better part of a century, it has been defined as one of two closely related subspecies that occupy a large swath of south Asia and several associated islands. The Burmese python and Indian python (Python molurus) are so closely related, in fact, that some scientists continue to argue their true familial ties. Physical differences between the snakes are minute, and include slight, but fairly consistent, variations in color pattern and scalation. But it is the reproductive preferences of these subspecies in the wild that poses perhaps the greatest argument for elevation of each to specific rank. Though interbreeding yields healthy offspring in captivity, there is an apparent reluctance between subspecies to mate in the wild, despite overlaps in the range of each. The ambiguities in their life histories yield two camps of thought—“splitters” who opt to maintain their sub-specific distinction, and “lumpers” who regard both races as a single species.

When viewed collectively, the species is a habitat generalist, capable of thriving in ecosystems spanning a variety of elevations—from sea level mangrove swamps to lower mountain forests sometimes as high as 3,000 feet. Its natural range extends to areas of both tropical and temperate climes—from semi-arid grasslands and deserts to wetlands of abundant rainfall. Regardless of where they are found, these pythons normally utilize the full gamut of natural features in an area, frequenting burrows, trees, rocky outcroppings, riparian zones, open water, and disturbed lands. In so doing, the snakes exercise their astonishing ability to swim, climb, and contort their bodies to meet the demands of the landscape. They are aided, of course, by tools forged over time through evolution: a supple skeleton, sinewy layers of muscle, and strong prehensile tails.

The species can adapt surprisingly well to hostile environmental conditions. In the northernmost reaches of its range, for instance, pythons are able to endure harsh winters during three-to-four-month periods of hibernation. In areas of constant inundation, the heavy-bodied pythons prove semi-aquatic in nature, comfortably spending significant time maneuvering their bulk both above and below the surface of the water. Pythons have also been known to persist in both disturbed and human environments, though it has been noted by some that they fare best amidst more natural habitats. And though it is also not their preferred haunt, pythons can even tolerate exposure to salt water for short periods of time while they comfortably navigate coastal waters.

Indian pythons and Burmese pythons occupy fairly distinct ranges south of the Himalayas. The former occupies nearly the entire South Asian subcontinent, where it is found primarily across large swaths of Pakistan, India, Nepal, and Sri Lanka. By contrast, Burmese pythons are generally encountered further east along a continuous range from northeastern India to southern China, with smaller, isolated populations also persisting in Nepal and on the islands of Java, Bali, Sumbawa, and Sulawesi. The details of natural distribution and biology are only partly known—informed by a limited collection of observations and studies from the field. But over the years, the study of captive animals has helped shed light upon the life histories of many snakes—particularly the Burmese python.

Hatching from the egg at only twenty inches, Burmese pythons experience one of the fastest growth rates known among snakes. During their first year of life, some can grow half a foot per month—particularly if fueled by regular feedings. Pythons reach sexual maturity sometime between reaching five and eight feet in length, a goal which can take as few as two to three years to achieve. The pace of growth slows gradually with age, but nonetheless permits both sexes to attain double-digit lengths. The females, however, typically dwarf their mates—sometimes reaching the length of a stretch limousine and tipping the scales at several hundred pounds.

To accommodate such growth, Burmese pythons readily consume any meal that satisfies their hunger. Diet is generally restricted to warm-blooded terrestrial animals, leaving a wide variety of potential prey on the menu. The python’s prowess at capturing, constricting, and consuming large prey has made it a staple of wildlife documentaries. But in addition to mind-boggling meals of leopards, deer, and antelope, the python feeds upon a much greater spectrum of both large and small fauna that includes wading birds, rodents, porcupines, bats, and domestic livestock. Though mammalian and avian prey is clearly preferred, the snakes are ultimately opportunistic in their feeding—known to consume even the occasional lizard, frog, or toad.

Cryptic coloration and a predilection for slow, deliberate movements provide an effective strategy for pursuing a meal. Burmese pythons are ambush predators that patiently lie in wait for their prey to advance. Engaged in attentive repose, pythons silently gather data using a sophisticated array of serpentine gadgetry—a sensitive inner ear transmits minute vibrations on the ground, a forked tongue processes molecules of odor captured from the air, and a full network of facial pits detects slight changes in temperature nearby. It is unclear whether it is motion, sight, or smell (or some combination thereof) that triggers the snake to feed.

Whatever the cue, it commands near-instantaneous strikes—widening jaws bearing rows of wretchedly recurved teeth capable of ensnaring an unsuspecting passerby. This bite, though no doubt painfully alarming, is nonfatal. Lacking venom, Burmese pythons must subdue their meal by sheer force. Using its mouthful of sharp barbs to hold fast the unfortunate captive, the snake throws coil upon coil around the body of its victim, exerting ever-increasing amounts of intense pressure. So strong is this fatal embrace it can at once squeeze breath from the lungs and render the heart inert. After some time, when movement is no longer detected, the large constrictor slowly relaxes its vicelike grip to finally indulge its appetite.

Though people are fascinated by the size, girth, and predatory instincts of the Burmese python, it is in other respects a fascinating biological creature of inspired design. Their seamless camouflage and capacity for stillness are well-developed traits that serve them not only in ambushing prey, but also constitute an effective strategy for self-preservation. A strong, prehensile tail allows them to hoist, suspend, and cantilever their bulk into trees high above the ground. The series of thermal pits that accents their lips allows for continued monitoring of their surroundings—enabling the detection of even minute differences in temperature nearby. And like other primitive snakes, Burmese pythons boast conspicuous pelvic spurs, which aid them in the requisite tickling and grasping that accompany courtship.

The reproductive habits of several python species are well documented, partly thanks to observations in the field, and partly due to the frequency and ease with which they are bred in captivity. Burmese pythons show great variability in the number of eggs they lay. While most will typically produce several dozen eggs at a time, both single-digit clutches and those in excess of 100 have also been reported. In captivity, females can be induced to lay a clutch every year, but in the wild they are more likely to produce a clutch every two to three years. During the time necessary for gestation and incubation a female python will often forgo all food—a prolonged period of four to six months during which she grows increasingly lean. Once her eggs are laid, a female python will swaddle her unhatched progeny in a protective stack of body coils. Should the ambient air begin to cool around them, the vigilant mother will begin to repeatedly contract the muscles in her lengthy body in a rhythmic fashion. As temperatures drop, these full-body spasms will grow ever more rapid and her coils will grow taller and tighter in a bid to generate heat for her unborn young. It is a display of maternal dedication rarely found among other reptiles, and a feat relatively unknown among cold-blooded animals—for a short span of time, she is actually capable of regulating her own body temperature for the benefit of her offspring.

Many facets of the life history of the Burmese python remain poorly understood. The extent of their distribution in certain portions of their native range still remains uncertain and in need of further study. The social workings of these large creatures remain somewhat shrouded in mystery, though observations of captive pythons provides some evidence to suggest a clear hierarchy may exist—particularly with regards to courtship. Both the density of Burmese python populations and the relative impact of disease and parasites on them still require further investigation. Even the full reproductive mechanisms of this species remain in question—some evidence exists that females may be capable of producing clutches of genetically identical young asexually through a process known as parthenogenesis.

The longevity of Burmese pythons in the wild also remains a great unknown. What little can be speculated about their span of life can only be gleaned through records of captives, some of which suggest exceptional animals can reach ages in excess of thirty years. In fact, one of the oldest known captive Burmese pythons died in 2009 at the ripe old age of 43. At the time of her passing, Julius Squeezer measured 18 feet long and weighed 220 pounds. Marty Bone, an avid snake enthusiast, had shared his home with Julius for 35 years, having acquired her as a full-grown adult. Bone attributed her exceptional longevity to both the freedom she enjoyed and the affection he showered upon her. Bone allowed Julius unfettered access to his home and, over time, she reportedly learned how to open doors merely by wrapping her body around doorknobs. Marty modified furniture in his home to better accommodate Julius, and even allowed her to curl up with him in bed. “At night she’d lay her head on me,” Bone recalled. “She was my bedmate, housemate . . . she was special to me.”

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Burmese pythons are strictly an Old World species. Still, much of our current knowledge about their natural history has come squarely from our experiences with them in the Western Hemisphere. Zoos, dealers, and private collectors have provided detailed information on their reproductive habits. University studies have furnished information on social behavior, feeding response, energy efficiency, and the effects of visual deprivation. Even the sad passing of Julius Squeezer in a private Utah home provided an important bit of data about potential species longevity.

The establishment of Burmese pythons in south Florida provided a simultaneous need, and opportunity, for further study and data collection. By 2006 it seemed evident that the python population in south Florida was growing larger. Just a few years prior, park employees were removing only two or three of them from the area annually (Figure 5). But beginning in 2002 the yearly figures began to make surprising jumps—staff removed 14 individuals in that year alone. The following year they removed 23 more. In 2004, the count jumped yet again to 70, then to 94 the following year. The park seemed poised to hit triple digits by 2006—a sobering milestone considering it only reflected those snakes that were captured and removed. The annual tallies didn’t include the many animals reported that subsequently got away. Nor did they reflect those that remained altogether unseen.

Increased awareness of the issue, the hiring of additional staff, a growing proficiency for capture, and a more concerted communications effort were all no doubt complicit in yielding higher rates of removal with every passing year. The clear statistical trend, however, was still unsettling. Evidence continued to mount suggesting the snakes were freely breeding in the wild. Park staff had thus far found pythons of various size classes throughout the Everglades, including juveniles. Newborn pythons had been recovered, some still bearing the ephemeral umbilical scars where their newly shed yolk sacs were once tethered. And several gravid females had been recovered—their innards packed to the walls with fertile eggs (Figure 6). Though the evidence of breeding was certainly compelling, it was not technically conclusive. Scientists had not yet happened upon the necessary “smoking gun”—neither copulation nor a nest site had been documented in the wilds of south Florida. To do so, scientists would need to learn as much as possible about the habits of this Old World serpent in its New World haunts.

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Exactly who is to blame for the introduction of Burmese pythons into the Florida Everglades is a topic of much speculation, interest, and heated debate. Those who found it difficult to fathom keeping large constrictors as personal pets were quick to point their fingers at those that actually did. After all, history had already shown a loose correlation between the increasing popularity of reptile ownership and the quickening pace with which new reptiles had begun to appear around homes and neighborhoods in south Florida. And for the most part, the same species popping up unexpectedly in the wild were largely the same scaly faces that could be found behind glass at the corner pet store. For many, it was logical to deduce that the pythons now proliferating in the Everglades were the latest example of a familiar cycle: impulse buys leading ultimately to accidental or intentional release.

In their defense, however, reptile enthusiasts and hobbyists adamantly refused to shoulder blame as a whole. Instead, many recognized that a small subset of irresponsible and inexperienced keepers could be found among them. If the pythons proliferating in the Everglades truly originated from the pet trade, it was not the fault of the overwhelming majority of diligent owners, but rather resulted from the negligent few who failed to provide proper enclosures, found themselves unprepared for the demands of ownership, or were simply too uninformed to know any better. Rather than malign an entire community of responsible reptile enthusiasts, they argued, energies would be better focused on better educating and regulating the irresponsible few.

But the irresponsible few remained difficult to find. Because people never believe themselves to be negligent keepers, no one ever stepped forward to volunteer their ineptitude or subject themselves to more stringent oversight. Nor did anyone ever plead mea culpa to the irresponsible handling of exotic wildlife. But even those who might have recognized some personal failure could still publicly divest themselves of any involvement in the growing python problem. Instead, they could clear their conscience by appealing to another popular scapegoat—the winds of Hurricane Andrew.

A Category 5 cyclone, Andrew dealt an infamously harsh blow to south Florida, culminating in the costliest natural disaster of its time. With peak winds of 165 miles an hour, the storm brutally punished communities in southern Miami-Dade County—flattening entire housing developments, snapping telephone poles and power lines, obliterating Homestead Air Force Base, and causing damage to Turkey Point Nuclear Power Plant. Andrew’s winds also hurled a seventeen-foot surge of water inland, leaving roads, yards, and trees littered with an incongruent placement of boats, traps, floats, and other flotsam. In its wake, the storm left behind over one billion dollars of losses in agriculture, and a totality of devastation that was difficult for victims to fully grapple with.

It is known that Hurricane Andrew was also responsible for the release of many captive animals from zoos, research facilities, and private collections in south Florida. Reports abound regarding the storm’s role in the appearance of rhesus monkeys, sacred ibis, Asian swamp hens, lionfish, and other species not formerly known to persist in the wild. One of the innumerable casualties reported in Andrew’s aftermath was a nascent reptile wholesaling business nestled on the outskirts of the Everglades in the then-rural town of Homestead. Housed in a flimsy former agricultural grow house, the facility was flattened during the storm, reportedly sending its thousands of cold-blooded occupants—including hundreds of baby Burmese pythons—into the howling atmosphere. Launched deep into the Everglades, it is believed by many that some of the snakes not only managed to survive the ordeal, but would go on to become the true progenitors of today’s problem population.

The “dispersal-by-tropical-cyclone” theory has been espoused by some and disputed by others. Contrary to the commonly accepted belief that today’s feral population is the result of numerous intentional or accidental releases over the years, genetic studies of populations recovered from the wilds of south Florida have revealed a close kinship among the animals. Those wanting to lay blame upon the furious winds of Andrew suggest these findings, coupled with known patterns of past importation, are in keeping with a single, large-scale release. Critics of this hypothesis, however, note that genetic similarity might only suggest a similarity of stock imported over time for trade. Furthermore, the remote outpost of Flamingo, from whence the population appears to have radiated, lies impossibly far from the former site of the reptile breeding facility. Had the storm resulted in a catastrophic release of individuals, how did they only find themselves in a remote expanse of tangled mangrove swamp over 40 miles away?

The debate over how Burmese pythons were introduced into the Everglades has led some observers unnecessarily into the weeds. In truth, documented encounters with large constrictors on the loose in Everglades National Park and elsewhere—including Burmese pythons—long predate the arrival of Hurricane Andrew. Irresponsible keepers had most certainly been implicated in the escape of snakes in the past. And yet, it was also entirely plausible that hurricanes and tropical storms could aid the release of far more. Numerous foreign species were documented to be running wild around south Florida in the still aftermath of Andrew. Reasonable minds could easily entertain the notion that the current problem unfolding in the Everglades could equally well be the result of accidental releases over time, a consequence of natural disaster, or some combination thereof. And to many, the argument was moot. Regardless of whether they were intentional or accidental, releases were occurring. And either by the hands of middlemen or end consumers, large constrictors bought and sold as personal pets were somehow making their way into one of North America’s most threatened habitats. The finer details regarding how they were introduced would never be known with certainty, but in truth, they weren’t all that important.

The convoluted arguments, allegations, and theories regarding how these reptiles had taken a foothold in the River of Grass provided a convenient distraction from considering broader, more important, questions. Finger pointing provided an effective schoolyard tactic for evading basic questions about why pythons are imported in the first place. Attempts to assign blame or critique efforts to eradicate the current population provided an ample rug beneath which to sweep larger, more complex issues of regulation, enforcement, and ethics. And for some, aggressive posturing provided an effective diversion from yet another important consideration—how efficiently the snakes were ravaging south Florida’s native inhabitants.