The largest reptile in North America, an adult alligator is a top predator, reaching almost 6 meters (20 feet) in length.
An airboat, a canoe, and a reputable local guide are essential when exploring the vast waterways that make up the Florida Everglades.
Catching a large cottonmouth in the Everglades. This species is highly venomous and known for its bad temperament.
Precariously balancing an HD camera and tripod in my canoe in preparation for a fill-in scenic sequence incorporating the gloomy surroundings of the Everglades.
An introduced species, the Burmese python, is now well established and breeding in the Florida Everglades, posing potentially catastrophic consequences for native fauna.
Ayers Rock—or Uluru, as it is now known—stands majestically alone under a stormy sky in the vast desert landscape of central Australia.
So named for their habitual north/south construction, the “magnetic” termite mounds of Northern Australia are unique to the territory and make for scenic pictures.
Underwater filming and catching of a sub-adult Australian freshwater crocodile in the Northern Territory.
A powerful predator, the beautifully marked perentie monitor lizard is Australia’s largest lizard, reaching over 2 meters in length.
Catching and removing a spectacled cobra from a public area.
Demonstrating the cobra’s defensive hooded posture for the camera.
The Asian cobras display a much shorter and more rounded hood than their African cousins.
While attracting a cobra’s attention with one hand, I am able to touch the back of its neck with the other, without fear of being bitten.
A rare sighting of a foraging white-coated black bear or “spirit bear” as it is known amongst the First Nations people of British Columbia, Canada.
A mother and sub-adult cub keep a watchful eye as the camera crew position themselves for some close-up filming.
When it is all said and done, after a long day of sweat and toil, any available free space is acceptable for a nap.
CHAPTER 15
SNAKE VENOMS AND THE FER-DE-LANCE
To produce a polyvalent antivenom (a single serum that is effective against the venoms of a group of snake species), a cocktail mix of snake venoms is introduced into the blood stream of a horse, in dilute, nonlethal proportions. These proportions are then gradually increased as antibodies form to combat the venoms. Eventually the horse’s system is capable of accepting a normally lethal dose of this snake-venom mixture without experiencing any ill effects whatsoever, the antibodies having increased sufficiently to overwhelm and neutralize the venoms. The animal is now immunized. Though any variety of animals may qualify to be used for this process, the domesticated horse holds the advantage of size, which allows for the draining of many liters of blood from it, making it the perfect animal for this process. The same horse may be used for many years, continuously supplying large quantities of its valuable immunized blood. The blood plasma contains the antibody and is separated and purified into crystal-clear, liquid serum. Some serums are produced in powder form, ready to be mixed with a saline solution before use. Some snake species require specific antivenom, and for these a monovalent serum is prepared.
Many antivenoms produced in the world today are polyvalent, covering a number of venomous species occurring in the same country or in close proximity to one another. This is a saving grace, as the need to positively identify the snake (though still an advantage) is no longer of primary importance—one serum may cover all the venomous species found in any one particular region. In most developed countries, snake-bite is a rare occurrence, with more people being killed by lightning than by snake-bite. However in some developing countries, where much of the population is rural, the incidence of snake-bite is far greater, sometimes numbering in the thousands each year.
Snake venoms are made up of an extremely complex mixture of enzymes and proteins, which scientists and biologists have not yet been able to duplicate. Thus, to continue the manufacture of antivenom, laboratories are forced to rely on suppliers who extract venom from living snakes. As discussed earlier, this is done by “milking” the venom from the snake, usually by allowing the reptile to bite through a thin plastic membrane stretched tightly over a conical flask, or in some cases, by massaging the venom glands while the fangs are supported over the edge of a collection container. Some snake species are capable of delivering large amounts of venom at each “milking,” while others, especially smaller species, may yield only minute quantities at a time. It would take roughly ten days for a “milked” snake to replenish the lost yield. Once extracted, the venom is freeze-dried, in which state it remains concentrated and toxic for any length of time. Considering the specific nature of the venom extraction business—the number of snakes required and the obvious difficulties, costs, and potential dangers present in collecting the venom—it is not surprising that snake venom has become a valuable product that is often in short supply.
Snake venom may be thought of as a modified digestive juice, and in fact venom does play a part in aiding the digestion of prey consumed by snakes. In the more highly developed species of snakes, however, the primary purpose of the venom is to kill the prey as quickly as possible. In the case of a dangerous amount of snake venom being injected into a human victim, an adequate amount of antivenom should be administered as soon as possible.
Antivenom is the most important element in the treatment of snakebite. Depending on how much venom has been injected by the snake will ultimately determine how much serum will be needed. This naturally varies greatly according to the species and size of the snake, how long the snake was attached to the victim, and the size of the victim. A small child will more quickly succumb to the effects of snake envenomation than an adult, for example. Considering that most highly venomous snakes need to inject no more than a drop of venom to potentially kill an adult human, it must be appreciated that most often many ampoules of serum will be needed to neutralize the symptoms arising from a serious bite. While this number may greatly vary from two to twenty—or more—in some cases as many as a hundred 10 ml ampoules have been required to save a life. Thus one can understand and appreciate the need to keep up a constant supply of snake venoms for the continued manufacturing of antivenom. And considering that there are roughly three hundred highly venomous snake species spread around the globe, one can only imagine how many snake ‘milkings’ would be required to keep up with demand.
In a somewhat different direction of exploration, still further demand for snake venoms has arisen as scientists probe deeper into the possibilities of using these venoms for medicinal purposes. Research has revealed that some snake venoms may hold the key to some of the worst human diseases. From research projects that are underway, there is evidence to suggest that snake venoms—or fractions thereof—can be used with surprisingly effective results. Cancer tumors in animals, for example, shrink when injected with certain venom extractions. Hemophilia, a bleeding disease, has been controlled in laboratory tests with clotting factors taken from the venom of the Russell’s viper of Asia. Drugs based on the venom of the Malayan pit-viper can be used to relieve phlebitis. Cobra venom can be made into a nonaddictive painkiller with the strength of morphine. Scientists have discovered that snake venoms are composed of as many as forty or more different proteins, so complex in nature that scientists are unable to duplicate them.
Considering all of this and the fact I was known to be travelling around the world on a quest to photograph venomous snakes, I was not surprised to be contacted by a venom research laboratory asking me to collect venom from certain species for analyses, should the opportunity arise. Though I had not practiced snake ‘milking’ for some years, I was of course well familiar with the technique from my days working at a snake and animal park, so I agreed. The research in question involved closely scrutinizing samples of venoms taken from wild specimens of the same species from different regions, which would afford the opportunity to study any variations in compos
ition. It was thought that what the same species of snake was feeding on in different regions might affect the toxicity and/or composition of the venom.
I had, over the years of my employment at snake parks, extracted venom from a wide variety of venomous snakes, depending on what species was available and what venom was required at the time. Unused serum, depending on how it is contained and housed, will expire after a certain number of years on the shelf, so generally speaking there is always a demand for fresh venom. Usually, under ideal conditions, extracting venom from snakes is a fairly simple task for the practiced herpetologist. “Milking” freshly caught venomous snakes on location in the field can prove to be a bit more uncoordinated and nerve wracking. Here conditions may be far from ideal, with very basic apparatus being employed in uncomfortable locations and most often involves handling angry, rebellious snakes, keen to retaliate to their handling with a deadly bite.
In Queensland, Australia, I came across a huge king brown snake curled up under the rotten floor boards of an old, disused wooden barn. Seeing that this enormous snake displayed few outward signs of distress or anger at my catching and handling of it, I considered it to be a perfect specimen for venom extraction, suspecting that it would deliver a good yield. And indeed it did, biting down firmly into the plastic membrane over the flask and injecting a huge amount of the deadly venom. When attempting to remove the fangs from the plastic membrane however, the snake refused to let go, biting down harder. Even after releasing my grip on the flask the snake held on tenaciously, leaving it dangling precariously from his jaws. Obviously excited that it was able at last to vent its frustrations it had so cleverly suppressed when first caught, the snake now pursued its path of revenge with a passion. Eventually I was forced to cut the elastic band securing the plastic membrane stretched over the top of the flask, allowing the membrane to collapse into the snake’s jaws while I removed the flask to safety. Still not dissuaded, the snake proceeded to stubbornly chew at the plastic and would surely have swallowed it had I not quickly extracted the membrane with a pair of forceps. It was a frightening reminder of just how dangerous these snakes could be if provoked. Had it gripped onto my arm and held on to it as it did to the flask, the amount of venom injected into my system would have secured my death that much quicker.
Spitting cobras are able to eject their venom more forcibly than other snakes. The venom of spitting snakes is also more fluid than that of other snakes, allowing it to be forced more freely through the fang openings. Thus, true spitting cobras have no need to throw their venom at an attacker (as is the case with the rinkhals) but instead are able to direct the venom spray in any desired direction by simply turning their head while contracting the muscles surrounding the venom glands. Considering that this venom spray may reach a distance of three meters, gives some indication of the force with which it is being ejected.
While filming an earlier episode of my reptile series one morning, I was astonished to find very obvious snake slither-marks in the sand surrounding my vehicle, in which I had bedded down the previous night. Knowing full well that a snake may be attracted to the warmth of a vehicle engine on a cold desert night, I was careful to check out all openings in the chassis for fear that the snake may still be present. As matters turned out, it was a wise thing to do, as I soon located the snake comfortably curled up on the engine block. Startled by the sudden movement and the sudden exposure to daylight as I lifted the hood, the snake quickly advertised its surprise, and its species, by raising its head and jetting a spray of venom in my direction. A Namibian spitting cobra! These snakes can grow to almost two meters long and are known to be quick to defend themselves, spraying copious amounts of venom in the hope of dissuading an attacker.
Fortunately, because of the ever-present desert glare reflected off the sandy floor, I had already donned my sunglasses, which prevented venom spray from entering my eyes, the only place it could cause me damage. Knowing there was a project underway to make a specific anti-venom for this species, I carefully untangled the snake from the wiring of the Nissan’s engine compartment and made preparations for a “milking.” The angered snake, meanwhile, continued to spray venom at my every movement until my sunglasses and the rest of my face and head were sticky with the stuff. Finally securing the snake behind the head, I introduced the customary flask with covered plastic membrane. Not expecting much, considering that the snake appeared to be expelling most of its venom at me, I was surprised to see two clear jetstreams of venom zing down into the flask with such force and duration as to make the flask vibrate in my hand. This continued for no less than four or five seconds, leaving the little flask almost a quarter filled with venom. I was astonished, but a further surprise lay in store.
It is a fact that venomous snakes control the amount of venom they deliver. A (more or less) lethal dose of venom is injected into a prey animal to kill it; usually a few drops is all it takes. A startled snake, on the other hand, instinctively striking out in a defensive mode, often delivers no venom at all. This situation is referred to as a “dry bite.” An angered snake, however, when offered the opportunity to vent itself by way of a premeditated, revengeful strike, will often deliver a much larger quantity of venom. The Namibian spitting cobra, angered by my handling, clearly demonstrated its dissatisfaction by first repeatedly spraying venom at me and then by ejecting a huge amount of venom through the plastic membrane into the flask, a technique designed to stimulate the snake into delivering venom through the false sensation of an actual bite. The cobra’s venom glands should, to all intents and purposes, by this time have been largely depleted, but when I released it a few minutes later, I was shocked to find myself once again under attack as the snake further vented its anger by once again showering me with streams of accurately directed venom. I was astonished! The snake seemed to possess an endless supply of stored venom, much of which it obviously had held back in spite of the ‘milking.’ I was aware, of course, that spitting snakes held a considerable amount of venom, but nothing had prepared me for this. Another lesson learned, as finally, with a disgusted last disdainful look in my direction, the cobra slithered away into the dry desert bushes.
Then came the day of my confrontation with the most vicious snake I have ever encountered in my entire career as a herpetologist—the giant fer-de-lance viper of Central America. I say “giant” because this particular snake, which would usually average about a meter to a meter and a half in length, measured over two meters in length, closer to two and a half meters, in fact. A formidable reptile in any herpetologist’s book, but also a species that I had been specifically asked to extract venom from, should I be so lucky as to encounter it.
The fer-de-lance, or lancehead viper, as it is commonly known because of its distinct, sharply triangular head and its frequent pattern of a dark arrow or lancehead marking, is a wide-ranging and prolific snake occurring from Mexico through Central America and into South America. These snakes have a virulent venom that destroys tissue and blood and are known to have caused many human fatalities. Like most snakes, this species will most often take flight when disturbed; if threatened, however, the fer-de-lance will defend itself vigorously. It is a species well known for its aggressive temperament and generally given a wide berth when encountered in the wild.
I had in fact come across two lance head vipers, both of which were of average size, during my several trips to film reptiles in South America. Of these, one clearly displayed its readiness to defend itself by striking out repeatedly on being approached, while the other slithered off at a hurried pace, apparently preferring escape to confrontation, as is more usual with most species of snakes. Being less than a meter in length, the first, more aggressive specimen posed little danger to me, as its striking distance was limited, which allowed me to comfortably get within range for some closeup photography. The Costa Rica episode, however, presented a different scenario—one that could have easily cost me my life.
There are basically three ways to find snakes in the wil
d, the first and most obvious being to physically search them out with methods applied according to the species you are after. Ground-dwelling snakes might be located under rocks or fallen tree stumps, etc., while arboreal species can be camouflaged amongst dense vegetation and hollow tree, and snakes known to eat frogs are usually found close to streams or dams. Therefore, depending on what species is being searched for, one can limit the search according to these basic principles.
The second method of reptile location can be employed if one is spending a fair amount of time in any one particular area of search. In this case it can prove productive to inform the locals of your quest, especially those laboring in the outdoors, as people spread out across a wider area naturally have more chance of encountering a snake while simply going about their everyday business. This can be especially beneficial in rural areas, where laborers may be planting, harvesting, or bush clearing. Word spreads fast, and generally workers will be only too pleased to have someone on call when a snake has been encountered.
To a lesser degree—but proven to produce effective results—is simply being alert to the cacophony of sounds reverberating from the surrounding wilderness in which you find yourself, especially where vegetation is dense and filled with a variety of insect, mammal, and bird calls. A sudden lull in the otherwise persistent screech of cicadas, for example, may indicate that something has disturbed them, while just the opposite is usual when birds are alerted to a foreign presence. I have on numerous occasions been made aware of the presence of a snake by the excited chattering of birds grouped together high up in a tree top, where I would otherwise never have spotted the reptile. In Costa Rica, however, it was a troop of capuchin monkeys that alerted me to the presence of the lancehead viper, which, in spite of its camouflage, had been detected by the monkeys’ excellent eyesight as the snake moved stealthily through the undergrowth.
Snakemaster Page 19
