Morley Read / Slow motion clip of a Linnaeus' sipo snake (Chironius exoletus) with open mouth, part of threat display, Amazon rainforest, Orellana Province, Ecuador. (non-ex)

Morley Read / Parrot snake (Leptophis ahaetulla) threat display, Amazon rainforest, Orellana Province, Ecuador. (non-ex)

Nick Garbutt / Sumatran pit viper (Trimeresurus sumatranus) juvenile on tree trunk, in tropical rainforest. Danum Valley, Sabah, Borneo, Malaysia.

David Tipling / Common European adder (Vipera berus) two males fighting over a female. Holt, North Norfolk, England, UK. April

David Tipling / Common European adder (Vipera berus) two males fighting over a female, Holt, North Norfolk, England, UK. April

David Tipling / Common European adder (Vipera berus) two males fighting over a female, Holt, North Norfolk, England, UK. April.

Fabio Pupin / Meadow viper, (Vipera ursinii), basking in alpine meadow, Apennines, Italy, September . Non-ex.

Fabio Pupin / Peringuey's desert adder, (Bitis peringueyi), sidewinding on dune, Namib desert, Namibia, February . Non-ex.

Daniel Heuclin / Horned viper (Vipera ammodytes) in natural setting, Turkey.

John Chan / Two male Southern Pacific rattlesnakes (Crotalus oreganus helleri) fighting during mating season. This behaviour is known as a "combat dance", and is used to determine dominance and the right to mate...

Paul Hobson / Parrot snake (Leptophis ahaetulla) in aggressive pose with mouth open. Costa Rica.

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