Lachesis

In Greek mythology, there are three goddesses of fate called the Moirai. Clotho (the spinner) whirls the thread of life on a distaff, Lachesis (the apportioner) measures the thread with her rod, and Atropos (the unturnable) cuts the thread with shears— irreversibly choosing a human’s time and manner of death. Inspired by these puppeteers of mortality, taxonomists have since named a genus of African vipers Clotho (currently Bitis), the bushmasters Lachesis, and the jumping pit vipers Atropoides. The second, Lachesis, is a genus of the largest vipers in the New World, comprising of four species, each reclusive denizens of old growth tropical rainforests. Legends of these formidable and seldom seen animals have been passed down for generations in Central and South America, bestowing a mythical quality to Lachesis… as it whistles throughout the night and wards off demons. My search for Lachesis had long been in vain, only hearing stories of the shushúpe (L. muta) in Peru and the infamous plato negro (L. melanocephala) of the Osa peninsula. This past summer, I was extremely lucky to experience my first bushmaster in the wild in Costa Rica. Here is the story of my encounter with an Atlantic bushmaster (L. stenophrys), also referred to as la matabuey or the “ox killer.”

High up the Cordillera Talamanca, we had heard of the appearance of a bushmaster near the homes of the Cabécar indigenous peoples. Over the course of a month or so, the snake had been spotted out in the open several times, all within a radius of about 20 meters around a deep burrow along a clay soil ridge. Because bushmasters have high site fidelity to their lair of choice, we decided to trek up to the spot for a chance to see this elemental serpent. We began our ascent by crossing the Pacuare River via a self-operated gondola suspended by a metal cable, then proceeded up the mountain. The routes in this area are regularly traversed by indigenous people, but because the rainforest constantly strives to subsume such paths, which direction to take can often be ambiguous. Landslides and treefalls, together with intersecting streams and cliffs make some segments impassable, so new trajectories must constantly be made. Colloquially, hikes up the mountain are called rompe pechos or “chest-breaking,” on account of your knees constantly coming up to touch your chest. Many times I found that hunkering down onto all fours and climbing (instead of walking) was more efficient… hoping that no terciopelos were lying in wait! On the whole, the routes are rather direct, going up and down sharply as opposed to being long and windy up to the top.

To reach our destination, we climbed one mountain, then back down on the opposite side to the east, and finally up another yet another mountain. It took us a full day’s worth of sunlight traveling through an amalgam of mostly dense understory and also open pasturelands. After an arduous journey, we were graciously taken in by a family that provided us with food and water, which we had naively left behind. By nightfall, the temperature had plummeted and the humid air transitioned into a cold drizzle. There is almost nothing that deters me from searching for tropical wildlife, especially at night, but being soaking wet and cold surely pushes me to my limit. Con los calzones mojados and no warmth or dryness left to spare, we took rest in preparation for our exciting day that was to follow. Lying above me as I slept was a voodoo charm of a silky anteater (Cyclopes didactylus) with a wasp’s nest in place of its head— not the way I anticipated first experiencing such a creature.

The following morning I awoke to a gorgeous view of the Turrialba volcano. Even from such a far distance, clouds of smoke and ash could be seen shapeshifting slowly and gradually over the serene bluish glow of the land. I’m not a morning person, but there is no better motivation to get moving at 5am than the possibility of an imminent bushmaster. The hike this morning was short and rugged, and although my knees are usually my strong suit, I’m not sure that my body was warm and flexible enough yet for a pleasant steep descent. Bushmasters have an affinity to ridges, and this one was no exception. It became increasingly difficult to walk upright without sliding onto the ground, and as I could barely keep myself in place… we had arrived. Clambering down and around an embankment and avoiding what would be a horrible rolling descent down the slopes, we looked up to a large hole positioned above us. My first thought was ‘oh no, this is the worst possible place to be when faced with a bushmaster.’ Just to peer inside a person would have to be positioned precariously, and in the event that the animal shoots out of its lair, there is no room for a graceful exit. My friend, Andrés, and I were on the same page and joked that the bushmaster would come flying out directly on top of us.

But was the bushmaster even home? Looking inside the cavity with a flashlight, we thought it was shallow and a dead end; only mud and white fungal growth were visible at first glance. Our hope waned a bit until we saw a glint of reflection low to the right within a narrow channel obscured by our light’s shadow. Tuberculate beige scales became discernible, then large black-rimmed triangles and a white belly. It was indeed none other than Lachesis. The bushmaster made not a single movement throughout all of our commotion, and it wasn’t until some gentle prodding that she turned to face me…

By this point, there was no doubt this bushmaster was a sizable animal, and a female to boot. She had small eyes relative to her head size, wide heat-sensing pits, and overall, a light color pattern, in contrast to males which tend to have more melanin. I was transfixed by her penetrating stare and flickering tongue, for a second almost forgetting about her lethality. These moments of getting “lost” during an encounter are my most treasured experiences in nature. For what feels like a timeless moment, it’s just me and the animal, while all other elements of the surrounding environment fade away and become irrelevant. Luckily, given the way she was situated, she would need to maneuver around the hole before being capable of delivering a strike. But soon enough, after a few minutes of patience, she made her move. In a mere instant, the bushmaster’s body rasped against the dirt and with her head raised, she rushed to appear outside of her refuge, nearly causing all of us to have a heart attack. Again, she ceased all movement, barely even turning her head as I continued moving around below her. I can’t imagine a more idyllic scene to gaze upon a bushmaster than what we experienced. As we looked up at her from below, struggling to maintain our composure and balance in the slippery mud, she appeared exactly the opposite— resolved in her intent, beautifully shrouded by ferns and raindrops in front of her lair. Whereas most animals would either defend or retreat, the bushmaster remained fixed in position. Andrés said if he could channel her thoughts, she would be thinking: “Who dares to mess with me?”

All photographs after slight disturbance [2] unless otherwise stated

Bushmasters spend most of their lives within mammalian burrows such as those of armadillos and pacas. However, without intimate knowledge of the habits and behaviors of specific individuals, it is almost impossible to find one in such a manner. As far as I’m aware, the vast majority of bushmaster sightings are of snakes found coiled out in the open, likely making use of higher temperatures above the ground for digestion. Andrés has mentioned that the protuberances of a bushmaster’s scales may aid in pushing through subterranean tunnels as they arch the head downwards and move forward and backward. Atypical for vipers, the dorsal part of the neck is tough and muscular, and there is almost no dip posterior to the jaw. Supposedly, the underside of the neck is comparatively delicate. Given the body weight of an adult bushmaster, handling must be performed with great care as to not injure the animal.

Spiked scale on the tail tip (~1.5 cm long); photographed after disturbance [4]. There are stories of Lachesis stinging people to death repeatedly with the tips of their tails, but in reality, these recounts hold no factual basis.

Lachesis is an outlier among New World vipers in its mode of reproduction. Whereas all others give birth the live young, female bushmasters lay over a dozen eggs, coiling around them for protection until hatching. Egg attendance behaviors in snakes are overlooked, but notable examples include nest building in king cobras and parental care in rattlesnakes. For bushmasters, their fossorial disposition and low detection rates have hindered our understanding of their habits. As if adults weren’t already hard to come by, juveniles are even more enigmatic; it is thought that they remain underground within the burrow system they hatch in, feeding on small mammals and marsupials. Like Atropoides, bushmasters will strike a prey item and bite down fiercely to prevent escape. This feeding behavior is the minority for vipers, which often quickly envenomate and release, eventually tracking down the victim through chemical cues after it flees and perishes.


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