It is huge,
rare and shrouded in mystique. No other snake in the New World
inspires such reverence and dread within us than the mighty bushmaster.
At over 4 meters, it is the largest viper in the world. And one
of the deadliest!
Myth and legend
surround this snake wherever it is found, and this is reflected
in its many vernacular names: the “Sucurucu”, the Brazilians believe,
can extinguish fires, and will suck the milk from cows and sleeping
women; the “Matabuey”, the Costa Ricans say can kill oxes; “Cascabel
muta” inspired Carolus Linnaeus, the founder of modern biological
nomenclature, to name it Crotalus muta, the silent rattlesnake.
Early explores to the New World returned with fanciful accounts
of this monstrous serpent laying waste to whole mule trains.
So impressed was Francois-Marie
Daudin, a late 18th century herpetologist, that he assigned the
bushmaster to its own genus, Lachesis, named after one of the
three fates in Greek mythology: Clothos, the spinner of life’s
thread; Lachesis, the drawer of lots, chose the length of one’s
thread; and Atropos made the final cut. Lachesis muta, the silent
arbiter of one’s fate!
So much for the myth:
what of the real bushmaster? Well it is a truly remarkable snake
in every way: reported to grow to 4.25 meters, the bushmaster
is by far the largest viper in the world. Only the king cobra
of Asia and the common taipan of Australia, both members of the
cobra family (the Elapidae), oust it from the title as largest
venomous snake in the world. It is the only viper in the New World
to lay eggs (oviparous); all the others bear live young (viviparous).
And, what few records there are of bites from this snake, suggest
an 80% mortality rate among humans, making the bushmaster the
most deadly snake in the Americas.
The bushmaster is rare,
though - perhaps fortunately so! Its narrow habitat requirements
confine the bushmaster to undisturbed, lowland primary rainforest.
In this it differs from its soul mate in terror, the terciopelo,
whose cosmopolitans habitat tastes bring it regularly into close
proximity to people. So for all its fame, the bushmaster is rarely
seen, whereas everybody is familiar with the terciopelo.
Bushmasters, like terciopelos
(and all other vipers), rely on stealth and camouflage to surprise
and ambush their prey. But, unlike the terciopelo, the bushmaster
has a very specific dietary habit: both young and adults eat almost
exclusively mammals, from mice to rats, agoutis and opossums.
Adult terciopelos will take rats and opossums, in addition to
frogs and lizards. But their young feed only on lizards and frogs.
The bushmaster and
all of its New World cousins belong to a sub-division of the viper
family, the Crotalinae, or pitvipers. They are so named because
they posses a pair of pits, one on each side of their heads, between
their nostrils and eyes. These pits function as infrared heat
sensors, enabling these vipers to detect the body heat of their
prey. Indeed, these pits are extremely sensitive to temperature
changes (to small fractions of a degree) and in effect function
as a second eye, allowing these remarkable snakes to see the world
in the infrared spectrum as well as in the visible spectrum of
The venom of the bushmaster,
and all other vipers, is a complex cocktail of toxic compounds.
Its primary function, like the venom from the other main group
of poisonous snakes, the cobras and allies, is to immobilize prey.
Cobra venom is termed a neurotoxin, and achieves this effect by
arresting the nervous function of its prey. Viper venom, termed
a haemotoxin, achieves the same result by disrupting the circulation
system, among other things. But viper venom has another trick
up its sleeve!
All snakes eat relatively
large prey, whole. And this presents them with a problem: how
to digest the animal before it rots from within. Most snakes solve
this problem by possessing powerful digestive systems. But vipers
have found a less costly solution: they inject venom that not
only kills the prey, but also begins the process of digestion
before the prey is even ingested. This digestive quality of viper
venom causes rapid tissue damage, however, and makes bites from
these snakes particularly nasty. Recovery from a cobra bite will
leave little or no visible evidence of the incident. Not so with
a viper bite: at best one will be left with unsightly local scaring
as a reminder. At worst, amputation!
Drop for drop, the
venom of the bushmaster is not as potent as many other venomous
snakes, but it is the shear volume of venom and the depth to which
its long fangs can inject it, that makes this pitviper so potentially
The bushmaster ranges
from Nicaragua through the rest of Central America into Colombia
and Ecuador in the west, and down into Brazil in the center and
east of South America. Within its range, four sub-species are
recognized. One of these four sub-species, Lachesis muta melanocephala,
is confined to the Osa. It differs from the other sub-species
by, among other things, the black coloration of the top of its
head – it is known locally as the “Plato Negro”. Another difference
is in the plato negro’s temperament. Researchers at Costa Rica’s
anti venom institute, the Instituto Clodomiro Picado, have informed
me that the Osa’s bushmaster is the most aggressive of them all
– the few locals who encountered this snake will attest to this
- and responsible for more casualties here than the other sub-species
of bushmaster elsewhere in the country.
Ground dwelling, ambush-hunting
snakes like the bushmaster, the terciopelo and the boa constrictor
rely on cryptic coloration of rhomboidal markings for concealment,
both to catch their prey and to hide from predators. When disturbed,
these species will remain still, at least initially, relying on
their camouflage for protection. Large, active hunting snakes
– all non-venomous, or only mildly venomous! - like tiger rat
snakes, sipos, mussuranas and cribos react to disturbance by fleeing
rapidly. These snakes are also more uniform in color, or at least
lack rhomboidal patterning. So if, like me, you delight in the
esoteric sport of snake-catching here is a rule of thumb: fast
moving, uniformly colored or striped snakes that live on the ground,
grab immediately; banded snakes, or rhomboidally colored snakes
that remain coiled when approached, hesitate initially, they may
be poisonous. This rule falls apart for arboreal snakes, however,
so it is wiser to leave all snakes alone!
In appearance, both
the bushmaster and the terciopelo look mean and menacing, and
some say even malevolent. The terciopelo, being a lance-head pitviper,
has pronounced triangular-shaped head. And, as its name implies,
the terciopelo has a velvet appearance to its skin. The bushmaster
in contrast has a more rounded, rattlesnake-like head, and skin
that is covered bead-like scales. The terciopelo, it is said,
caries with it an aura of neurotic unpredictability; the bushmaster,
an aura of calculated malevolence. Few animals for me embody the
spirit and mystique of wild, pristine rainforest like the majestic
this article, new information about the taxonomic status of the
infamous bushmaster has come to my attention. As indicated above,
the bushmaster was considered to be one species, with several
geographic sub-species. Recent biometric evidence, however, has
raised the level of three of these sub-species to specific status:
The South American species, Lachesis muta, the Central
American bushmaster, L. stenophrys, and the black-headed
bushmaster of the Osa, L. melanocephala.
a biologist, wilderness expedition guide, and the president of
Osa Aventura. You can contact him at at firstname.lastname@example.org