In popular culture, books and films are filled with tales of deadly venomous snakes attacking humans. However, in the rainforests of the Amazon basin snakes are not aggressive, and will usually only bite a human when disturbed and fearing for their own safety.
South America’s Amazon basin is home to at least seventeen species of highly venomous snakes, including seven species of pit viper and ten species of coral snake. The pit vipers of the Amazon include the bushmaster (Lachesis muta), which at more than 2.5 meters (8 feet) in length is the biggest venomous snake in the Americas. However, while this snake has gained a fearsome reputation, very few of the snakebites inflicted on humans have ever been attributed to this species, which tends to feed on small rodents.
It is another pit viper, the more inoffensive looking one meter-long (3 feet) fer-de-lance (Bothrops atrox), common to tropical northern South America but only recorded in Peru around the northern Tumbes area, which is responsible for the greatest percentage of snakebites in South America, probably due to its habit of living in the vicinity of human settlements, rather than to any particularly aggressive tendencies.
One of the venomous snakes found in Tambopata National Reserve is the so-called false fer-de-lance (Xenodon rabdocephalus), a rather nondescript brown snake with gray markings, which grows to around 80 centimeters (30 inches) in length.
Species of coral snake also vary considerably in size, from the 50 centimeter (15 inch) pigmy black-backed coral snake (Micrurus scutiventris) to the 1.80 meter (6 feet) Amazon coral snake (Micrurus spixii).
As their name suggests, coral snakes tend to be brightly colored. But, while in nature bright colors are usually a danger signal, indicating that the species in question is highly venomous (as in the case of many tropical snakes and frogs), the rainforests of the Amazon basin are also home to species known as false coral snakes, which are in fact completely harmless. However, it can be extremely difficult to distinguish between a coral snake and a false coral snake, and so caution is advised whenever a brightly-colored serpent is spotted on forest trails.
Snakes use sophisticated detection systems in order to locate their prey. Their tongues are vital sensory organs, and they flick them repeatedly as they gather information about the terrain they are moving through.
Species of pit vipers are known to employ thermo-receptors located in the facial pits that give them their name, producing infrared thermal images with which they identify their prey. According to researchers, a pit viper’s thermal imaging system is so sensitive it is able to detect the temperature variation caused by a small rodent 15 centimeters (6 inches) away.
When venomous snakes strike, their venom is administered to the victim via hollow fangs that operate in the same way as hypodermic needles, the human invention that snake fangs inspired.
Fascinatingly, members of the Amazon basin’s dangerous fer-de-lance genus have also contributed to humanity, through the discovery of the angiotensin converting enzyme (ACE) inhibitors that control blood pressure and thereby extend the lives of those suffering from hypertension.