Shattil & Rozinski / Bullsnake {Pituophis catenifer sayi} ready to strike, Colorado, USA

Gabriel Rojo / South american terns {Sterna hirundinacea} at nest colony, Valdez peninsula, Argentina

Gabriel Rojo / South american terns fighting {Sterna hirundinacea} Valdez peninsula, Argentina

Bryan and Cherry Alexander / Polar bear (Ursus maritimus) mother protecting her already mauled cub from the large male that attacked it. Cape Churchill, Manitoba, Canada.

Tim Laman / Two Gentoo penguin chicks (Pygoscelis papua) squabbling, Antarctica, February

Bernard Castelein / Avocet (Recurvirostra avosetta) birds in territorial dispute, Texel, the Netherlands

Bernard Castelein / Blackbuck (Antilope cervicapra) two males fighting, Rajasthan, India

Bernard Castelein / Blackbuck (Antilope cervicapra) two males fighting, Rajasthan, India

David Tipling / Steller's sea eagle {Haliaeetus pelagicus} and White-tailed sea eagles {Haliaeetus albicilla} squabbling over fish, Akan, Hokkaido, Japan, February

David Tipling / Southern Giant Petrel {Macronectes giganteus} feeding on seal carcass, South Georgia

Bernard Castelein / Blackbuck (Antilope cervicapra) two males fighting, Rajasthan, India

Bernard Castelein / Avocet (Recurvirostra avosetta) two birds in territorial dispute, Texel, the Netherlands

Bernard Castelein / Greylag Goose (Anser anser) showing aggression, hissing, Texel, the Netherlands

Wild Wonders of Europe / Unterthiner / Eleonora's falcon (Falco eleonorae) pair on rock, Andros, Greece, September 2008

Juergen Freund / Men with roosters about to begin a cockfight, Philippines. 2008

Juergen Freund / Spectators watching a cockfight, Philippines. 2008

Juergen Freund / Spectators watching a cockfight, Philippines. 2008

Juergen Freund / Men preparing rooster for cockfight, Philippines. 2009

Juergen Freund / Men setting Roosters down to begin cockfighting, Phillipines. 2008

Juergen Freund / Men setting Roosters down to begin cockfight, Phillipines. 2008

John Cancalosi / Ring-billed gull (Larus delawarensis) adults fighting in air, NY, USA

John Cancalosi / Western grey kangaroos {Macropus fuliginosus} young males sparring, South Australia

Steve Knell / Bullfinch (Pyrrhula pyrrhula) two males fighting, Norway, January 2007

Richard Du Toit / African elephant {Loxodonta africana} male on bank of Chobe river looking threatening, low angle shot, Chobe NP, Botswana

Shattil & Rozinski / Mule deer {Odocoileus hemionus} males fighting, Colorado, USA

John Cancalosi / Griffon vulture fighting over deer carcass {Gyps fulvus} Spain

Peter Blackwell / Spotted hyaena {Crocuta crocuta} defending food from Black backed jackal {Canis mesomelas} Kenya

Peter Blackwell / Spotted hyena {Crocuta crocuta} being attacked by others in the group, Masai Mara, Kenya

Richard Du Toit / Hippopotamus {Hippopotamus amphibius} male threat display, Moremi Wildlife Reserve, Botswana

Shattil & Rozinski / Ferruginous hawks fighting {Buteo regalis} Colorado, USA

Shattil & Rozinski / Puma snarling {Felis concolor} Colorado, USA, captive

John Cancalosi / Western grey kangaroo {Macropus fuliginosus} males fighting, Australia

Peter Blackwell / Topi sparring {Damiliscus lunatus} Masai Mara GR, Kenya

Peter Blackwell / Topi sparring {Damiliscus lunatus} Masai Mara GR, Kenya

Peter Blackwell / Lappet faced / Nubian vulture {Torgos tracheliotus} & Black backed jackal in dispute over carcass. Masai Mara, Kenya

Richard Du Toit / Sub-adult Black browed albatross {Thalassarche melanophrys} chasing off White chinned petrel (Procellaria aequinoctialis), South Africa

Bernard Castelein / Blackbuck {Antilope cervicapra} two males fighting, Thar desert, Rajasthan, India

Todd Pusser / Black-footed albatross (Phoebastria nigripes) fight over Grey whale blubber from killer whale attack. California.

TJ Rich / Indian elephant aggressive display {Elephas maximus} Minneria NP, Sri Lanka

Steve Knell / Coots fighting {Fulica atra} UK

DAVID TIPLING / Grey seal bull attempting to mate {Halichoerus grypus} Norfolk, UK