David Tipling / Brown hare (Lepus europaeus) boxing in spring North Norfolk, England, UK. May.

Dietmar Nill / Two European hares (Lepus europaeus) boxing in a snow covered field, Germany, March.

Andy Rouse / Mountain hares (Lepus timidus) boxing in snow, Scotland, UK, December.

Erlend Haarberg / Mountain hares (Lepus timidus) boxing, Vauldalen, Sor-Trondelag, Norway, May.

Nick Garbutt / Southern elephant seal (Mirounga leonina), two males, equally matched with mouths open in aggression. Out of focus King penguin (Aptenodytes patagonicus) colony in background. Gold Harbour, South Geor...

Steven David Miller / Eastern grey kangaroo (Macropus giganteus), two males fighting. Grampians National Park, Victoria, Australia.

Steven David Miller / Eastern grey kangaroo (Macropus giganteus), two males fighting. Grampians National Park, Victoria, Australia.

Heather Angel / Pere David's deer (Elaphurus davidianus) two stags boxing amongst herd of hinds. Captive bred in reserve after reintroduction from Woburn Abbey, England, UK. Dafeng Milu National Nature Reserve, J...

Heather Angel / Amur / Siberian tiger (Panthera tigris altaica), two sparring in snow. Captive in tiger park, Heilongjiang Province, China. February.

David Tipling / Brown hare (Lepus europaeus) boxing in spring North Norfolk, England, UK. May.

Erlend Haarberg / Mountain hares (Lepus timidus) backlit, fighting at night, Norway. April.

Erlend Haarberg / Mountain hares (Lepus timidus) backlit, fighting at night, Norway. April.