David Shale / Fang Tooth {Anoplogaster cornuta} close-up of head showing teeth, from the Mid-Atlantic Ridge, 2600m

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.

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.

Christophe Courteau / Peringuey's adder (Bitis peringueyi) buried in sand, flicking tongue, hunting, Namib Desert, Namibia.

Tony Phelps / Cape cobra (Naja nivea) spreading its hood, retreats into hole, De Hoop Nature Reserve, Western Cape, South Africa, January.

Tony Phelps / Cape cobra (Naja nivea) emerging from a Cape gerbil (Gerbilliscus afra) burrow, hunting and smelling with its tongue, De Hoop Nature Reserve, Western Cape, South Africa, January.

Tony Phelps / Cape cobra (Naja nivea) hunting, chasing a Cape gerbil (Gerbilliscus afra), De Hoop Nature Reserve, Western Cape, South Africa, December.

Silke Arndt / Western rattlesnake (Crotalus viridis viridis), threat display, South Dakota, USA, September.

John Cancalosi / Western diamondback rattlesnake (Crotalus atrox), defensive rattling, Arizona, USA, April.