Daniel Heuclin / Great basin Gopher Snake / Bullsnake (Pituophis catenifer deserticola) head profile, controlled conditions, Joshua Tree National Monument, California USA

Sandesh Kadur / Large scaled pit viper (Trimeresurus macrolepis) head profile, water droplet below, Western Ghats, Southern India

Laurie Campbell / Male Adder (Vipera berus) basking on rock, Northumberland National Park, England, May

Pete Oxford / Eastern indigo snake (Drymarchon couperi) The Orianne Indigo Snake Preserve, Telfair County, Georgia, USA, threatened species, captive

John Cancalosi / Boa Constrictor (Boa constrictor) shedding skin from head. Guanacaste National Park, Costa Rican tropical rainforest.

John Cancalosi / Boa Constrictor (Boa constrictor) shedding skin from head. Guanacaste National Park, Costa Rican tropical rainforest.

Sven Zacek / Grass Snake (Natrix natrix) looking out from between wood slats. Estonia, Europe, June.

Klaus Echle / Black Viper / Adder (Vipera berus) head in profile. Black Forest, Germany, June.

Daniel Heuclin / White-lipped / Green tree viper (Cryptelytrops albolabris) captive, from SE Asia

Pete Oxford / Sipo Snake (Chironius exoletus) head against a white background. Captive. Endemic to Mindo Cloud Forest, Ecuador.

Juergen Freund / Researchers Guido and Katja Westhoff work in a mobile lab in the bush. To handle the deadly Common death adder (Acanthophis antarcticus) Guido puts the head and upper portion of the snake in a plastic...

Juergen Freund / Close-up of a Horned sea snake (Acalyptophis peronii) resting its head on its coils. Queensland, Australia, February