Benjamin Barthelemy,Benjamin Barthelemy / Ibex (Capra Ibex) fighting, Aiguilles Rouges National Nature Reserve, Haute-Savoie, France, June

David Pattyn / Coots (Fulica Atra) fighting in early morning light. Valkenhorst Nature Reserve, The Netherlands, Europe. April.

Ben Cranke / Southern elephant seals (Mirounga leonina) subadult males practice sparring. St Andrew's Bay, South Georgia Island

Markus Varesvuo / Two male Black grouse (Tetrao / Lyrurus tetrix) fighting at lek. Utajarvi, Finland, April.

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

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

Claudio Contreras / Guadalupe fur seal (Arctocephalus townsendi) male fighting, Guadalupe Island Biosphere Reserve, off the coast of Baja California, Mexico, April

Edwin Giesbers / Dalmatian pelican (Pelicanus crispus) group squabbling over fish, Lake Kerkini, Greece.

Tony Heald / Red Deer (Cervus elaphus) stags fighting during the rutting season. Bushy Park, London, UK. October.

David Pattyn / Scarlet Macaw (Ara macao) couple fighting in a tree Corcovado National Park, Osa peninsula, Costa Rica

David Pattyn / Scarlet Macaw (Ara macao) couple fighting in a tree Corcovado National Park, Osa peninsula, Costa Rica

Tui De Roy / Black rhino (Diceros bicornis) and White rhino (Ceratotherium simum), being harrassed by playfighting White rhino bull, Solio Game Reserve, Laikipia, Kenya. September.

Oscar Dewhurst / Eurasian coot (Fulica atra) males fighting over territory. London, England, UK. December.;

Tui De Roy / Wolf giant tortoise (Chelonoidis becki) two males fight briefly over mating rights. Wolf Volcano, Isabela Island, Galapagos

Danny Green / Red Deer Stags (Cervus elaphus) fighting amongst the bracken. Bradgate Park, Leicestershire, UK, October.

Guy Edwardes / Hawfinch (Coccothraustes coccothraustes) fighting in snow, Bulgaria

Danny Green / Reindeer (Rangifer tarandus), two play fighting in snow. Svalbard, Norway, April.

Danny Green / Polar bear (Ursus maritimus) female and cubs play fighting. Svalbard, Norway, March 2018.

Ann & Steve Toon / African elephants (Loxodonta africana) herd silhouetted at sunset. Chobe National Park, Botswana.

Alex Mustard / Two female Common seahorses (Hippocampus kuda) fighting over territory on the seabed. The brief fight was preceeded by a ritualised, synchronised parade. Bitung, North Sulawesi, Indonesia. Lembeh Stra...

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.

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

SCOTLAND: The Big Picture / RF - Black Grouse (Tetrao tetrix), two males fighting on lek , Scotland, UK.April (This image may be licensed either as rights managed or royalty free.)

Terry Whittaker / RF - Two Red foxes (Vulpes vulpes) on hind legs play fighting, Netherlands. (This image may be licensed either as rights managed or royalty free.)

Terry Whittaker / Red foxes (Vulpes vulpes) fighting in sand dune habitat, Holland, Netherlands. November.

Marie Read / American avocets (Recurvirostra americana) two during aggressive (territorial) encounter, Bear River Migratory Bird Refuge, Utah, USA, May.

Marie Read / Canada geese (Branta canadensis) two during territorial fight in early spring, Ithaca. New York, USA

David Tipling / Common European adder (Vipera berus) two males fighting over a female. Holt, North Norfolk, England, UK. April

David Tipling / Common European adder (Vipera berus) two males fighting over a female, Holt, North Norfolk, England, UK. April

David Tipling / Common European adder (Vipera berus) two males fighting over a female, Holt, North Norfolk, England, UK. April.

David Pattyn / Alpine ibex (Capra ibex) adult males fighting in alpine landscape, Valsavarenche, Gran Paradiso National Park, Aosta Valley, Italy, May

Matthew Maran / Red Fox (Vulpes Vulpes) cubs play fighting North London, England, UK, June.

Klein & Hubert / Mustang stallion kicking out after winning fight. Rocky Mountains, USA, June.

George Sanker / Arctic tern (Sterna paradisaea), two fighting in mid-air. Machias Seal Island, New Brunswick / Maine, Canada / USA. July.

Tony Wu / View down the throat of a male Zoarchias major eelpout (Zoarchias major) that has opened its mouth during a confrontation with another male. Yamaguchi Prefecture, Japan. Pacific Ocean.

Tony Wu / Two male Zoarchias major eelpouts (Zoarchias major) engaged in a mouth-to-mouth confrontation. Yamaguchi Prefecture, Japan, Pacific Ocean.

Tony Wu / Zoarchias major eelpouts. (Zoarchias major) The orange individual is female, the one in the hole is male. The female has approached the male, curled around him, attempting to dislodge the male from th...

Tony Wu / Zoarchias major eelpout (Zoarchias major) with her mouth wide open. Yamaguchi Prefecture, Japan, Pacific Ocean.

Staffan Widstrand / Wild Wonders of China / Pere David's deer / Milu (Elaphurus davidianus), two stags testing their strength in Hubei Tian'ezhou Milu National Nature Reserve, Shishou, Hubei, China