The Bush Master (Lachesis muta)

Aug 09, 2009 Features / Columnists, Interesting Creatures in Guyana

The Bush Master (Lachesis muta) is a venomous pit viper species found in South America. Two subspecies are currently recognized, including the nominate subspecies described here.
Adults grow to an average of 2 to 2.5 metres (m), although 3m is not too unusual. The largest recorded specimen was almost 3.65m long, making this the largest of all pit vipers and the longest venomous snake in the western hemisphere.
The head is broad and very distinct from the narrow neck. The snout is broadly rounded. There is no canthus. A pair of small internasals is present, separated by small scales. The supraoculars are narrow. Other parts of the crown are covered with very small scales. Laterally, the second supralabial forms the anterior border of the loreal pit, while the third is very large. The eye is separated from the supralabials by 4-5 rows of small scales.
The body is cylindrical, tapered and moderately stout. Mid-body there are 31-37 nonoblique rows of dorsal scales which are heavily keeled with bulbous tubercles and feebly imbricate. There are 200-230 ventral scales. The tail is short with 32-50 mainly paired subcaudals, followed by 13-17 rows of small spines and a terminal spine.

A bushmaster secluded in its habitat

The colour pattern consists of a yellowish, reddish or grey-brown ground colour, overlaid with a series of dark brown or black dorsal blotches that form lateral inverted triangles of the same colour. The lateral pattern may be precisely or indistinctly defined, normally pale at the centre.
Lachesis is one of the three Fates in Greek mythology and was supposed to assign to man his term of life — something this species is certainly capable of doing. The species is similar in appearance to rattlesnakes and vibrates its tail vigorously when alarmed, but has no rattle and was therefore called mutus (later muta), which is Latin for dumb or mute. However, when in the undergrowth, the tail actually makes quite a loud rustling noise.
Found in South America in the equatorial forests east of the Andes: Colombia, eastern Ecuador, Peru, northern Bolivia, eastern and southern Venezuela, Guyana, Suriname, French Guiana and much of northern Brazil. The species is also found in Trinidad.
They are found in primary and secondary forests; adjacent fields and cleared areas. In Trinidad it tends to prefer hilly and mountainous regions.
Some reports suggest that this species produces a large amount of venom that is weak compared to some other vipers. Others, however, suggest that such conclusions may not be accurate. These animals are badly affected by stress and often do not last long in captivity. This makes it difficult to obtain “good, healthy” venom for study purposes.

For example, Bolaños (1972) observed that venom yield from his specimens fell from 233 mg to 64 mg while they remained in his care. As the stress of being milked regularly has this effect on venom yield, it is reasoned that it may also affect venom toxicity. This may explain the disparity described by Hardy and Haad (1998) of the low laboratory toxicity versus the high mortality rate of bite victims.[11]
The most famous of the vipers in Guyana is the Bushmaster (Lachesis muta). This snake is aptly named in English and particularly in Latin – as the “silent bringer of death.” The bushmaster, known as the surucucu in Brazil, and the shushupe in other countries, is the largest venomous snake in the New World. These snakes can regularly exceed 2,000 millimetres in length (6.5 ft.), and one of the largest recorded was 4,267 mm (14 ft.).
Like the rattlesnake, it has a prominent dorsal ridge, and the head is broad with an upturned snout. The bushmaster is a nocturnal snake, and reported as extremely aggressive, although scientists believe this to be an exaggeration.
(Source – Wikipedia: The Free Online Encyclopedia)