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

Lucas Bustamante / Red tailed boa constrictor (Boa constrictor constrictor) juvenile, portrait, with tail wrapped round head, Cuayabeno, Sucumbios, Ecuador.

Nick Garbutt / Yellow Anaconda (Eunectes notaeus) in vegetation at the edge of the Paraguay River, Taiama Reserve, western Pantanal, Brazil, South America.

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

Chris Mattison,Chris Mattison / Rubber Boa (Charina bottae) in defensive posture, raising tail to mimic head. California, USA, November.

Morley Read / Slow motion clip of a Garden tree boa (Corallus hortulanus) flicking its tongue, Amazon rainforest, Orellana Province, Ecuador. (non-ex)

Morley Read / Slow motion clip of a Garden tree boa (Corallus hortulanus) flicking its tongue, Amazon rainforest, Orellana Province, Ecuador. (non-ex)

Cyril Ruoso / Malagasy ground boa (Acrantophis madagascariensis) camouflaged in leaf litter. Anja Community Reserve, Madagascar.

Cyril Ruoso / Madagascar ground boa (Acrantophis madagascariensis) swallowing adult Ringed-tailed lemur (Lemur catta). Madagascar.

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

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