Franco Banfi / Close view of a Green anaconda, (Eunectes murinus) underwater, Formoso River, Bonito, Mato Grosso do Sul, Brazil

Luciano Candisani / Green Anaconda (Eunectes murinus) female constricting male after copulation, after which she will consume him, Brazil

Franco Banfi / Green anaconda (Eunectes murinus) underwater, flicking tongue, Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Green anaconda (Eunectes murinus) swimming inFormoso River, Bonito, Mato Grosso do Sul, Brazil

Claus Meyer / Green Anaconda (Eunectes murinus) moving through wetland vegetation, Pantanal ecosystem, Brazil

David Pattyn / Green Anaconda (Eunectes murinus) , Cuyabeno wildlife reserve, Sucumbios, Ecuador, July

David Pattyn / Green Anaconda (Eunectes murinus) , Cuyabeno wildlife reserve, Sucumbios, Ecuador, July

Franco Banfi / Green anaconda, (Eunectes murinus) underwater, Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Close view of a Green anaconda, (Eunectes murinus) underwater, Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Green anaconda, (Eunectes murinus) underwater, Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Close view of a Green anaconda, (Eunectes murinus) underwater, Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Green anaconda, (Eunectes murinus), Formoso River, Bonito, Mato Grosso do Sul, Brazil

Sylvain Cordier / Common anaconda (Eunectes murinus) Amazonas, Brazil.

Francois Savigny / Spectacled caiman {Caiman crocodilus} preying on male Green anaconda {Eunectes murinus} , Llanos, Venezuela, South America

Francois Savigny / Female Green anaconda 'tasting' air with tongue {Eunectes murinus} Llanos, Venezuela

Cyril Ruoso / Anaconda (Eunectes murinus murinus) Pacaya-Samiria National Reserve, Amazon, Peru.

Christophe Courteau / Giant Anaconda (Eunectes murinus) close up of scales, Hato El Cedral, Llanos, Venezuela.

Christophe Courteau / Giant Anaconda (Eunectes murinus) close up of body, Hato El Cedral, Llanos, Venezuela.

Christophe Courteau / Giant Anaconda (Eunectes murinus) Hato El Cedral, Llanos, Venezuela.

Christophe Courteau / Giant Anaconda (Eunectes murinus) Hato El Cedral, Llanos, Venezuela.

Christophe Courteau / Giant Anaconda (Eunectes murinus) Hato El Cedral, Llanos, Venezuela.

Christophe Courteau / Giant Anaconda (Eunectes murinus) Hato El Cedral, Llanos, Venezuela.

Franco Banfi / Green anaconda (Eunectes murinus) underwater in Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Green anaconda (Eunectes murinus) underwater inFormoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Green anaconda (Eunectes murinus) Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Green anaconda (Eunectes murinus) surfacing to breathe, Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Green anaconda (Eunectes murinus) surfacing to breathe, Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Scuba diver photographing Green anaconda (Eunectes murinus) Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Green anaconda (Eunectes murinus) Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Detail of the skin of Green anaconda (Eunectes murinus) on the side of Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Cuvier's Dwarf Caiman (Paleosuchus palpebrosus) Recanto Ecologico, Rio da Prata, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Green anaconda (Eunectes murinus) on the edge of Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Green anaconda (Eunectes murinus) on the edge of Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Green anaconda (Eunectes murinus) Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Green anaconda (Eunectes murinus) underwater in Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Green anaconda (Eunectes murinus) close up underwater in Formoso River, Bonito, Mato Grosso do Sul, Brazil

Franco Banfi / Green anaconda (Eunectes murinus) on river edge, Formoso River, Bonito, Mato Grosso do Sul, Brazil

Mark Carwardine / Green anaconda (Eunectes murinus) in water, captive, from South America

Mark Carwardine / Green anaconda (Eunectes murinus) in water, captive, from South America

Pete Oxford / Green Anaconda (Eunectes murinus) in tree, Tiputini River, Yasuni National Park, Amazon Rainforest, Ecuador

Mark Bowler / Green / Common Anaconda (Eunectes murinus) and fishermen in the background. Pacaya Samiria National Park, Amazon rainforest, Peru.

Mark Bowler / Green / Common Anaconda (Eunectes murinus) in water. Pacaya Samiria National Park, Amazon rainforest, Peru.

Mark Bowler / Green / Common Anaconda (Eunectes murinus) in water, regurgitating caiman after being disturbed by fishermen. Pacaya Samiria National Park, Amazon rainforest, Peru.

Mark Bowler / Green / Common Anaconda (Eunectes murinus) in water. Pacaya Samiria National Park, Amazon rainforest, Peru.

Luciano Candisani / Green Anaconda (Eunectes murinus), Pantanal, Brazil

Pete Oxford / Green anaconda (Eunectes murinus) in river, Rewa River, Iwokrama Reserve, Guyana

Pete Oxford / Green anaconda (Eunectes murinus) in river, Rewa River, Iwokrama Reserve, Guyana

Pete Oxford / Green anaconda (Eunectes murinus) on rainforest floor, Rewa River, Iwokrama Reserve, Guyana

Pete Oxford / Green Anaconda (Eunectes murinus) juvenile, Iwokrama Rainforest Reserve, Guyana

Pete Oxford / Green Anaconda (Eunectes murinus) surfacing to breath near tadpole on leaf, Rewa River, Iwokrama Rainforest Reserve, Guyana

Pete Oxford / Green Anaconda (Eunectes murinus) on riverbank, Rewa River, Iwokrama Rainforest Reserve, Guyana

Pete Oxford / Green Anaconda (Eunectes murinus), Rewa River, Iwokrama Rainforest Reserve, Guyana

Murray Cooper / Green Anaconda (Eunectes murinus) climbing up tree with tongue extended, Amazon, Ecuador

Mark Bowler / Arowana fishermen and Green anaconda {Eunectes murinus} after disturbing it from its resting place during sustainable arowana fishing, Rio Yanayacu, Pacaya-Samiria National Park, Peru, october 2008

Thomas Marent / Green Anaconda (Eunectes murinus) being held up by two men, Leticia, Colombia

Thomas Marent / Green Anaconda (Eunectes murinus), Leticia, Colombia

Luciano Candisani / Green Anaconda (Eunectes murinus) constricting a Piraputanga (Brycon microlepis) in small tributary of Formoso River, Cerrado Ecosystem, Brazil

Matthew Maran / Green anaconda {Eunectes murinus} enters water to avoid being bitten by horseflies {Tabanidae} Note blood spot in centre, Cuyabeno Reserve, Amazon Basin, Ecuador

Ingo Arndt / Green Anaconda (Eunectes murinus) close up, portrait of head, Amazon ecosystem, Peru

Ingo Arndt / Green Anaconda (Eunectes murinus) in rainforest leaf litter, Amazon ecosystem, Peru

Heidi & Hans-Juergen Koch / Green Anaconda (Eunectes murinus) young snake in water with duckweed, species is largest snake on earth and can reach 11 meters in length, native to tropical South America

Claus Meyer / Green Anaconda (Eunectes murinus) moving through wetland vegetation, Pantanal ecosystem, Brazil

Claus Meyer / Green Anaconda (Eunectes murinus) moving through wetland vegetation, Pantanal ecosystem, Brazil

Claus Meyer / Green Anaconda (Eunectes murinus) captured, Pantanal ecosystem, Brazil

Claus Meyer / Green Anaconda (Eunectes murinus), Pantanal ecosystem, Brazil

Claus Meyer / Green Anaconda (Eunectes murinus) moving through wetland vegetation, Pantanal ecosystem, Brazil

Claus Meyer / Green Anaconda (Eunectes murinus) moving through wetland vegetation, Pantanal ecosystem, Brazil

Francois Savigny / Green anaconda large female head portrait Llanos Venezuela {Eunectes murinus}

Francois Savigny / Green anaconda large female head portrait Llanos Venezuela {Eunectes murinus}

Francois Savigny / Green anaconda large female Llanos Venezuela {Eunectes murinus}

Joel Sartore / Photo Ark / Green anaconda (Eunectes murinus) portrait, Amphibian Foundation, Atlanta, Georgia. Captive, occurs in South America.

Joel Sartore / Photo Ark / Green anaconda (Eunectes murinus) portrait, Amphibian Foundation, Atlanta, Georgia. Captive, occurs in South America.

Fernando Faciole / Green anaconda (Eunectes murinus) curled up on log. Cristalino State Park, Alta Floresta, Mato Grosso, Brazil.

Karine Aigner / Portrait of a Green anaconda (Eunectes murinus) with botflies on his head. Yasuni National Park. Ecuador. Amazon Rainforest.

Morley Read / Green anaconda (Eunectes murinus) juvenile on tree trunk in rainforest, near the Rio Tiputini, Amazon rainforest, Ecuador.

Morley Read / Green anaconda (Eunectes murinus) juvenile on tree trunk in rainforest, near the Rio Tiputini, Amazon rainforest, Ecuador.

Morley Read / Revealing shot of Green anaconda (Eunectes murinus) juvenile on tree trunk in rainforest, near the Rio Tiputini, Amazon rainforest, Ecuador.