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Common names: South American bushmaster, more.
Adults grow to an average of 2 to 2.5 m, although 3 m is not too unusual. The largest recorded specimen was almost 3.65 m 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. Midbody 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.
The color pattern consists of a yellowish, reddish or grey-brown ground color, overlaid with a series of dark brown or black dorsal blotches that form lateral inverted triangles of the same color. The lateral pattern may be precisely or indistinctly defined, normally pale at the center.
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, Surinam, French Guiana and much of northern Brazil. The type locality is "Surinami" (Surinam).
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.
|Subspecies||Authority||Common name||Geographic range|
|L. m. muta||(Linnaeus, 1766)||South American bushmaster||Colombia, eastern Ecuador, Peru, northern Bolivia, eastern and southern Venezuela, Guyana, Surinam, French Guiana and much of northern Brazil|
|L. m. rhombeata||(Wied-Neuwied, 1824)||Atlantic forest bushmaster||Coastal forests of southeastern Brazil (from southern Rio Grande do Norte to Rio de Janeiro).|
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- Lachesis muta (TSN 209556). Integrated Taxonomic Information System. Accessed on 25 October 2006.
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- Bolaños R. 1972. Toxicity of Costa Rican snake venoms for the white mouse. Amer. Jour. Trop. Med. Hyg. 21:360-363.
- Hardy DL Sr, Haad JJS. 1998. A review of venom toxinology and epidemiology of envenoming of the bushmaster (Lachesis) with report of a fatal bite. Bull. Chicago Herp. Soc. 33(6):113-123.
- O'Shea M. 2005. Venomous Snakes of the World. Princeton University Press. 160 pp. ISBN 0-691-12436-1.
- Zamudio KR, Greene HW. 1997. Phylogeography of the bushmaster (Lachesis muta: Viperidae): implications for neotropical biogeography, systematics and conservation. Biological Journal of the Linnean Society, 62:421-442. PDF at Cornell University, Department of Ecology and Evolutionary Biology. Accessed 26 October 2006.