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...

Robert Valentic / Red-bellied Blacksnake (Pseudechis porphyriacus) basking on rock, Lerderderg Gorge, Victoria, Australia, February.

Chien Lee / Minden / Black-headed Cat Snake (Boiga nigriceps) swallowing alive Harlequin Flying Tree Frog (Rhacophorus pardalis) prey, Kubah National Park, Sarawak, Malaysia, sequence 1 of 4

Claudio Contreras / Texas indigo snake (Drymarchon melanurus erebennus) close up amongst Vervain (Glandularia sp.) flowers, Laredo Borderlands, Texas, USA. April

Alex Mustard / Butterfish (Pholis gunnellus) portrait. Gardur, south west Iceland. North Atlantic Ocean.

Colin Varndell,Colin Varndell / White Legged Snake Millipede (Tachypodoiulus niger) three coiled, Dorset, UK, September.

Michael D. Kern / Black headed cat eye snake (Boiga nigriceps) captive, from SE Asia

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

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

Steve Nicholls / Skeleton of a Python (Python sp)

James Christensen / Black-naped Forest Racer (Dendrophidion nuchale), Mindo, Ecuador

Paul Hobson / Grass snake (Natrix natrix) swimming amongst duck weed, Oxfordshire, UK