Atlantic bushmaster, Lachesis muta, Southern american bushmaster, Atlantic bushmaster
Lachesis muta, also known as the Southern American bushmaster or Atlantic bushmaster, is a venomous pit viper species found in South America, as well as the island of Trinidad in the Caribbean. Two subspecies are currently recognized, including the nominate subspecies described here.
Southern American bushmasters are venomous pit vipers found in South America. They are the third longest venomous snakes in the world. Their head is broad and distinct from the narrow neck. The snout is broadly rounded. The color pattern consists of a yellowish, reddish or grey-brown ground color, overlaid with a series of dark brown or black dorsal blotches; these blotches form lateral inverted triangles of the same color. The lateral pattern may be precisely or indistinctly defined, normally pale at the center.
Southern American bushmasters occur in South America east of the Andes: Colombia, eastern Ecuador, Peru, northern Bolivia, eastern and southern Venezuela, the island of Trinidad in the Republic of Trinidad and Tobago, Guyana, Costa Rica Surinam, French Guiana and much of Brazil. These snakes live in rainforests; adjacent fields and cleared areas. In Trinidad, they prefer hilly and mountainous regions.
Southern American bushmasters are very secretive and lead a solitary life. They are crepuscular and prefer to hunt after dark. Like most New World pit vipers, South American bushmasters exhibit defensive tail vibration behavior in response to potential predatory threats. They vibrate their tail vigorously when alarmed, but have no rattle and were therefore called 'mutus' (later 'muta'), which is Latin means dumb or mute. However, when in the undergrowth, their tail actually makes quite a loud rustling noise.
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 are not accurate. These animals are badly affected by stress and rarely live long in captivity. This makes it difficult to obtain venom in useful quantities and good condition 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) between the low laboratory toxicity of the venom and the high mortality rate of bite victims.
Brown (1973) gives the following LD50 values for mice: 1.5 mg/kg IV, 1.6–6.2 mg/kg IP, 6.0 mg/kg SC. He also notes a venom yield of 200–411 mg. The bushmaster's venom has proteolytic activity, which destroys and causes lesions in the tissue, anti-coagulant, which causes incoagulable blood, hemorrhagic and neurotoxic, that acts mainly on vagal stimulation. The symptoms are quite similar to those caused by Bothrops, at the site of the bite there is pain, edema, ecchymosis, skin necrosis, abscesses, vesicles and blisters. The main complications at the bite site include necrosis, compartment syndrome, secondary infections and functional deficit. The systemic effects are characterized by hypotension, dizziness, visual disturbances, bradycardia, abdominal pain, nausea, vomiting and diarrhea. Other manifestations are also similar to Bothrops, including systemic hemorrhage and kidney failure. In ilhéus, Bahia, Brazil, a 7-year-old boy was bitten when he left the house and stepped on one of these specimens, which then readily bit him; death was reported to have occurred approximately 15 minutes later. In 2005, in northwest Mato Grosso, a 5-year-old child also died, going into shock approximately 30 minutes after being bitten by a Lachesis muta and succumbing within 90 minutes.
Southern American bushmasters are carnivores; they eat mainly small mammals, such as rats and mice.
Southern American bushmasters breed year-round. Females lay 5-19 eggs, usually in abandoned burrows. They guard their nests during incubation and only can leave briefly to drink. The incubation period lasts around 60-79 days. Hatchlings measure 30 to 50 cm at birth; they are completely independent and can take care of themselves. Young Southern American bushmasters become reproductively mature at 4 years of age.
The main threat to Southern American bushmasters is habitat destruction caused by urbanization and the expansion of agriculture.
Since the diet of Southern American bushmasters consists mainly of rats and mice, these snakes play an important role in the ecosystem by helping reduce and control rodent populations.
