Wildlife Articles of the Osa

Tales from the Jungle: Snakes
by Mike Boston of Osa Aventura

Snakes are my passion - or one of them! They were my father’s passion too, when we lived in Trinidad and Tobago. He bequeathed his passion to me, as I have done to my daughter. I have been associated with snakes all of my life: I have kept them, bred them, caught them, rescued them and released them; they have excited me, scared me, embarrassed me, bitten me and shit on me!

Snakes stirs us all, deeply. We have an innate fear of them, indeed, so does much of the animal kingdom. Snakes hold this revered position by virtue of the venomous members of their ranks. Our culture, its myths and legends abound with references to snakes. They are revered and reviled wherever they occur, and often slaughtered as a result. Our combined feelings of revulsion and fascination towards snakes could hardly be more eloquently articulated than by the words of Alexander Skutch, a passionate birder and coauthor of A Guide to the Birds of Costa Rica. I quote: “The serpent crams itself with animal life that is often warm and vibrant, to prolong an existence in which we detect no joy and no emotion. It reveals the depth to which evolution can sink when it takes the downward path and strips animals to the irreducible minimum able to perpetuate a predatory life in its naked horror. The contemplation of such an existence has a horrid fascination for the human mind and distresses the sensitive spirit.”

I don’t share Skutch’s feelings, though most of us do. I hold snakes to be one of the most beautiful, precise and lethal carnivores ever to have been sculpted by evolution. Ideed, they are the most successful terrestrial carnivores ever to have lived on Earth, and out number all other terrestrial carnivore species many times over.

Morphologically, they have nothing in excess. Snakes are without limbs, ears and eyelids - but as though to be compensated, evolution has equipped each snake with two penises! However, despite their morphological frugality (or perhaps because of it!), snakes move and hunt in any realm with pernicious economy.

The most commonly expressed fear by people I take into rainforests of Corcovado concern snakes. The fear of snakes expressed by two women I was about to take into Corcovado was uncommonly intense, however. In fact, they were about to cancel the tour when I told them that I don’t carry anti-venom with me. I barely managed to persuade them to go when I exclaimed “don’t worry, you very rarely see snakes!” The women were only partially convinced when we stet off by taxi to Carate, the southern gateway to Corcovado. The mischievous side of me prayed we would find a snake!

Whether it is a figment of my imagination or not, it certainly seems to be the case that there is an inverse relationship between a persons desire to see snakes and their likelihood of seeing them. I seem to find more snakes when in the company of those who dread them most! Never was this paradoxical phenomenon better illustrated to me than in the events that were about unfold as we set off to explore Corcovado.

“You never see snakes, huh!” remarked one of the women as the taxi driver pointed out a large, electric blue keel-backed racer, Chironius carinatus, on the road a short distance ahead. I just can’t resist catching snakes and, despite the protests from the women, I burst out of the taxi and ran towards the snake. Keel-backed racers are fast diurnal hunters, with large eyes and keen vision. They are wary snakes, and one cannot afford finesse when attempting to catch them. So I lunged at the snake, just as it was about to disappear into the undergrowth, and seized it by the tail. The snake turned and struck at my face, but with reflexes of a prize boxer I dodged, and the snake missed.

I now had six feet of angry snake suspended from my grasp. Meanwhile, protests from the taxi were reaching fever pitch: “No, Mike!” “please don’t, Mike!”

Me with a boa on the road to Carate

Me with a boa on the road to Carate

The snake then bit my knee, released and struck again at my chest. In the process of getting the snake into a more manageable position it bit me several times more on my left arm. With the snakes head now under control and my knee, chest and arm oozing rivulets of blood, I approached the taxi. I had a huge grin on my face – my prayers were answered, I thought!By the time I reached the taxi the snake had settled down in my gentle grasp. The expressions on the women’s faces were ones of total disbelief. They were aghast and speechless. My enthusiastic dissertation on snakes, extolling their abundant virtues, went largely unheard!

I released the snake, wiped the blood from my arm, chest and knee, and jumped into the taxi. The women were amazed that I was still alive, and examined my bite wounds minutely, and repeatedly. They said I was a complete lunatic and begged me to desist from such activities lest I die, and leave them abandoned in the jungle. But, of course, I didn’t!

In fact, I caught several more snakes during the course of our explorations of Corcovado over the coming three days – more than normal! But, their regard for snakes gradually transformed from one of dread to fascination. Indeed, towards the end of our tour, the women were searching for snakes as enthusiastically as me.

“You lied to us!” one of the woman exclaimed. “Yes, you did!” the other agreed, before they both burst into laughter over a farewell drink. “We had a great time though!”


This curios affinity between snakes and ophiophobes was evident on another occasion, while I was working at Mapache Lodge on the Rio Sierpe. Two Canadian couples arrived for a three-night stay at the Lodge, bent on exploring the Osa’s rainforests. There was one problem, though: one of the women was terrified of snakes.

Our frequent forays into the jungle were for her a nightmare. Every time we returned to Mapache Lodge her relief was palpable. She felt safe there!

However, her illusion of safety in the confines of the Lodge was shattered on the second evening while they were sitting around a table on the verandah. I stood beside the table talking to them when the husband of the woman said, in a matter-of-fact way: “ I think you had better move, darling!”

Directly above her head a common tree boa, Corallus hortulanus, was dangling from the rafters, stretched vertically, intent on reaching her head. The boa’s intent was ultimately to reach the floor, but it was funny that it chose her head out of the five that were there to achieve its objective.

It amuses me how perspectives among us can be so different in a given circumstance. I see the jungle and its creatures, especially snakes, as things of beauty and fascination. The perspective this woman held could hardly have been more different. This incident reinforced in her the conviction that jungles are hell, caldrons of serpentine nightmares. She slept little that night and insisted on leaving the next day. A day early!


One of my most embarrassing incidents involving snakes was when I took a pleasant and modest Italian couple on a night tour of the Rio Sierpe. This river is a superb venue for nighttime, wildlife forays as its waters and banks team with crocodiles, caimans and snakes, the eyes of which glow red in a flashlight beam.

Julio, the owner of the lodge at which I then worked, steered the boat diligently between the rafts of water hyacinth that drifted down the river. Armed with a one million candlepower spotlight, I scanned the water and banks for telltale eyes. I had just released a small crocodile, which I had caught to illustrate to the Italian couple the virtues of these delightful beasts, when I noticed red eyes from vegetation on the nearby bank. I knew that it was a snake, and in all probability a common tree boa.

With my spotlight fixed on the spot, Julio docked the boat, bow first, on the muddy bank. I gave the spotlight to the Italian woman. She illuminated the unfolding scene for her husband to video. Armed with my flashlight I jumped ashore and approached the snake. It was a particularly large common tree boa. Gently, I retrieved the snake from the low vegetation. It was a two-handed operation, though, and I had to hold my flashlight in my mouth. With the boa entangling my both arms, I headed back to the boat. The Italian couple excitedly videoed the drama.

However, mounting the bow of the boat, with both my arms occupied, proved difficult. It was when I raised my leg to attempt the operation that my trouser snake made an untimely appearance from the leg of my shorts!

A diplomatic silence pervaded the air. With a video pointed at me, and the power of a million candles illuminating my embarrassment, I could do absolutely nothing but continue to mount the boat.

Having done so, I attempted to draw attention to the snake while simultaneously maneuver my John-Thomas back to its proper, more seemly position without hands. Having achieved partial success in this matter, and having delivered my talk extolling the virtues of the lithesome beast occupying my both arms, I turned, knees together, and delivered the snake back from whence it came. Diplomacy was maintained, and nothing was said. I prayed that the video wouldn’t be screened on television at a later date, on one of those most funny home video shows!


Rescuing a common tree boa near Sierpe village

Rescuing a common tree boa near Sierpe village

While living at Mapache Lodge, some distance up the Rio Sierpe from the village of Sierpe, I took it upon myself to rescue snakes from the machetes of ohiophobic locals. I received considerable cooperation, particularly from Don Marino from La Palma. He presented me with many fer-de-lances caught by his farm workers.

Journeying to La Palma from Mapache Lodge to collect Don Marino’s offerings involved a boat journey, two bus journeys and an overnight stay in Cabinas at La Palma. I often muse over what the reactions of the drivers and passengers would have been had they asked me what I was carrying aboard the buses on my frequent journeys!

For some reason, my appeals to the local people to spare snakes, and allow to save and release them, yielded mostly fer-de-lances. I would keep these snakes at Mapache Lodge for a period before releasing them. My collection grew!

At one point I had fourteen snakes, seven fer-de-lances and seven assorted species, variously acquired. I had at this time been making plans to set up a snake breeding facility at the lodge, and had been in consultations with the Clodomiro Picado for permission to do so. They were very supportive towards the project, which left me only to deal with the paper work. I, therefore, kept the snakes now in my possession to stock my proposed facility.

Feeding these snakes was a problem. I acquired three pairs of laboratory rats as a solution, and prepared to breed them to satisfy the growing appetites of my burgeoning menagerie. I waited, and waited, but the rats refused to breed. Meanwhile, I had only an infrequent and inadequate supply of trapped rodents from the Lodge’s kitchen to satisfy the appetites of my snakes. So I now found myself in the annoying situation of having six stubborn, celibate rats and fourteen hungry snakes. In a fit of pique I released all of my snakes except one, an injured boa constrictor, and verbally threatened the rats with execution. (I like rats, and having to feed them to my snakes is one the aspects of snake husbandry I dislike most.)

It was not long, however, before the rats started breeding. I now found myself in the equally annoying situation of having one well-fed boa and a growing surplus of rats. A snakes’ economy also applies to its diet. Being heterothermic, snakes require a mere fraction of the food that a homoeothermic bird or mammal of equivalent size requires. My boa’s appetite thus couldn’t keep apace with my rat’s procreativity. My problem was by this time further compounded by the fact that the Lodge was due to close and that I was about to leave. The snake-breeding project was shelved and I was now faced with the prospect of having put down over fifty rats, a prospect I didn’t relish.

A solution presented itself in the form of a forty-pound boa constrictor. Henry, the Lodge’s caretaker, and his brother had come across this boa while working on their father’s farm. They had ushered it into a cage for me to collect. With delight, I set off with Henry by boat to his father’s farm.

Approaching twelve feet in length, this boa was one of the largest I had ever seen - and one of the meanest too! It retracted its head into the strike position and hissed menacingly when I approached its cage. It stuck violently at me, but missed. Quickly, I grabbed the boa behind the head and proceeded to draw it from the cage. It’s hissing intensified. To control this large snake I had to subdue its head in my right arm, its’ hind end with my left arm and drape the bulk of its’ body around the back of my neck and shoulders. Unable to bite me, the boa discharged its next line of defense: shit! It delivered a payload of several pounds of its fetid turds down my chest and legs. The smell was horrendous!

Henry and I installed the boa at Mapache Lodge, and left it for a few days to settle into its new surroundings. Once settled, I began delivering rats to it. The boa ate them without hesitation, six at a sitting. Over the next month this boa gained considerably in weight as it disposed of all my rats. I released it, along with the convalescing boa, and left Mapache Lodge.


Being bitten by a snakes, large boas, pythons and venomous species excepting, is really quite an innocuous experience. Despite their formidable reputations, snakes are light boned and fragile creatures. Because snakes eat relatively large prey whole, the bones of their jaws are necessarily light, designed to disarticulate during swallowing. Lined with needle-like teeth, the jaws of snakes function to hold onto rather than crush prey. Therefore, snakes do not have a powerful bite.

A good friend of mine, Philip Davison, and I took being bitten by animals to an art form. We met at university in Portsmouth, southern England, as a result of our common interest in reptiles. Between us, we kept veritable menagerie of snakes and lizards. Frequent bites from our reptiles and our macho boastings about them conspired to engender spirited of competition between us. Eagerly we would place our fingers in the jaws of any reptile that was willing to bite them.

Consequently, we both lost our fear of being bitten. Although we reserved a respect for venomous snakes, and never deliberately allowed ourselves to be bitten by one, that respect was starting to diminish. Meanwhile our catalogue of bites was growing along with our boasts: I had the bite from a powerful three-foot tegu (a large South American lizard) atop my list of credits; Philip had matched that with the bite from a nine-foot reticulated python.

One day we both added baby European adder bites to our lists. Some time previous we had caught twenty-four adult adders, and from those had kept three gravid females. On that day, the adders produced between them about thirty babies. They were the most delightful little snakes, and mean too. We bagged the babies and prepared to release them. But first, we could not resist putting our hands into the bag to let the mass of babies bite us - which they did with gusto! The experience was like putting our hands into a bunch of stinging nettles!

Some days later, Philip greeted me with big grin on his face. He couldn’t wait to tell me that one of his cane-break rattlesnakes had bitten him. Fortunately for him it was a dry bite, causing only a little localized swelling. He was so proud of his wound and displayed it to every one. He knew that it would be a hard act for me to follow. He was right!

Today, some twenty-five years hence, we find ourselves together again on the Osa Peninsula, still indulging our passion for reptiles. We meet frequently on reptile forays, and often handle coral snakes and the lance-head vipers of the area. But to this day, Philip can still boast that he has been bitten by a more dangerous reptile than has ever bitten me.


On night tours, I like to demonstrate to my clients the amazing alarm call of the smoky forest frog, Leptodactylus pentadactylus. This large frog emits a loud series of shrieks when captured, reminiscent of a crying baby. It has been speculated that this alarm call, emitted naturally when seized by a predator, is meant to attract other predators to the scene. If a scuffle between the predators then ensues, the frog may be given a chance to escape.

The likelihood of this speculation being true was suggested to me recently in Corcovado Park. I had brought three people on a canoe trip up the Rio Sirena, an awesome river that flows from the Corcovado lagoon to the sea near Sirena Station. The Rio Sirena teams with fish, including huge snook and snapper, which support a healthy population of bull sharks and crocodiles - I have encountered bull sharks several miles up river! It is also a favorite with tapirs, which spend a good portion of their time swimming in the river and browsing on vegetation from along its banks. A conoe trip along the Rio Sirena can be very rewarding to the keen adventurer and naturalist.

About three miles up river, the Rio Pavo is joins the Rio Sirena. From this point onwards, the Rio Sirena changes in character. Its flow becomes more sluggish, lush growths of water vegetation sprout from its bed and rafts of water hyacinth cling to its banks. Shoals of curious snapper swarm in the crystal clear water, and often emerge from the among the water plants to follow our canoe. Northern jacanas, purple gallinules, anhingas, Muscovy ducks and other water birds abound. So do crocodiles!

It was on this stretch of the Rio Sirena, while savoring the natural ambience from under the shade of a large fig tree, that my fellow canoers and I heard a strange noise coming from the forest on the far bank. A first we paid the little heed to the noise, but its persistence began to draw our attention.

The noise was strangely familiar to me, yet I couldn’t put my finger on its identity. A jaguar or puma cub perhaps, I speculated. We grabbed our paddles and made our way the far bank to investigate.

Quietly, I got out of the canoe, ascended the bank and surveyed the scene. Perched on low vegetation, directly above the source of the noise, were two common black hawks, looking down intently. As I approached they flew off revealing a huge snake trying to swallow a large smoky forest frog, rump first. The snake, a black-tailed cribo, Drymarchon corais, was perhaps the largest colubrid (typical snake) that I had ever seen. It was now that I realized why the noise seemed familiar to me. I am well acquainted with the alarm call of the smoky forest frog, but hearing it out of context, namely during the day, had confused me.

I beckoned the others to come, and together we looked on in amazement. The huge cribo wrestled with the frog, trying in vane to swallow it, oblivious to our presence. The smoky forest frog shrieked repeatedly while struggling to get away. The scene was a gruesome one and I fought against helping the hapless frog. Though, I did take the opportunity of stroking the cribo while its mouth was occupied. It nudged my hand away with a coil of its body, and continued its task. We left and let nature take its course.

The struggle between the two combatants had been going on for ten minutes or more when we arrive, and continued until we were out of earshot, some fifteen minutes later. The cribo was too large for the common back hawks to deal with, but I wonder what would have happened if the racket had attracted the attention of one the large cats? Would the cribo have fared so well? I doubt so. In that scenario, perhaps the frogs shrieking could have saved its life!

To be continued……

Mike Boston is a biologist, wilderness expedition guide, and the president of Osa Aventura. You can contact him at at info@osaaventura.com