Robert Valentic / Eastern tiger snake (Notechis scutatus) female, Yarra River corridor in suburban Melbourne, Victoria, Australia, in mid-summer. She is in a defensive pre-strike position with hood expanded, accompanie...

Nick Garbutt / Yacare Caiman (Caiman yacare) gaping to regulate its body temperature, with attendant hoverflies, the Paraguay River, Taiama Reserve, western Pantanal, Brazil, South America.

Bence Mate / Dalmatian pelicans (Pelecanus crispus) low angle perspective of open bills, Lake Kerkini, Greece, February. Highly Commended, 2011 Wildlife Photographer of the Year competition.

Juergen Freund / Yellow ribbon eel / Ribbon moray eel (Rhinomuraena quaesita). Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Yellow ribbon eel / Ribbon moray eel (Rhinomuraena quaesita). Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Blue ribbon eel / Ribbon moray eel (Rhinomuraena quaesita). Lembeh Strait, North Sulawesi, Indonesia.

Mark Taylor / Baby Jackdaw (Corvus monedula) gaping to be fed

Colin Varndell / Blue tit brings caterpillar to young in nestbox {Parus caeruleus} UK

Charlie Summers / Arctic grayling (Thymallus arcticus) male gaping at the approach of another male in the background. North Park, Colorado, USA. June.

Nick Garbutt / Gathering of sunbathing Yacare caiman (Caiman yacare) at the edge of a lagoon. Some gaping to regulate its body temperature +thermoregulation). Northern Pantanal, Mato Grosso, Brazil,

Charlie Summers / Arctic grayling (Thymallus arcticus) male gaping which is a sign of aggression, North Park, Colorado, USA.

Loic Poidevin / Eurasian hoopoe (Upupa epops) at nest in stone wall with hungry chicks gaping, Vendee, France, June