Sandesh Kadur / Southern lechwe (Kobus leche), two males about to fight, facing each other. Okavango Delta, Botswana.

Chris Gomersall / Great skua (Stercorarius skua) attacking adult Northern gannet (Morus bassanus) in flight. Boreray, Saint Kilda, Scotland. June 2009.

Erlend Haarberg / Common redpoll (Acanthis flammea) males fighting Vauldalen, Norway, April. .

Kim Taylor / Braconid wasp (Braconidae) trying to lay an egg on a Lesser willow sawfly (Nematus pavidus) larva, which pushes the wasp away with its body. Controlled conditions.

Kim Taylor / Braconid wasp (Braconidae) trying to lay an egg on a Lesser willow sawfly (Nematus pavidus) larva, which pushes the wasp away with its body. Controlled conditions.

Kim Taylor / Lesser willow sawfly (Nematus pavidus) larva trying to drive away a parasitic Braconid wasp (Braconidae). Controlled conditions.

Kim Taylor / Braconid wasp (Braconidae) trying to lay an egg on a Lesser willow sawfly (Nematus pavidus) larva, which pushes the wasp away with its body. Controlled conditions.

Kim Taylor / Lesser willow sawfly (Nematus pavidus) larva trying to drive away a parasitic Braconid wasp (Braconidae). Controlled conditions.

Kerstin Hinze / Two Piebald shrews (Diplomesodon pulchellum) fighting. Captive, native to Turkmenistan and Uzbekistan.

Kerstin Hinze / Two Piebald shrews (Diplomesodon pulchellum) digging and fighting. Captive, native to Turkmenistan and Uzbekistan.

Tui De Roy / Flightless cormorant (Phalacrocorax harrisi), pair fending off dying Galapagos marine iguana (Amblyrhynchus cristatus). El Nino resulted in starvation of iguanas. Cape Douglas, Fernandina Island, Gala...

Tui De Roy / Nazca booby (Sula granti), adult killing chick. Genovesa Island, Galapagos.

Tui De Roy / Nazca booby (Sula granti), adult with chick that it has killed. Genovesa Island, Galapagos.

Tui De Roy / Nazca booby (Sula granti), adult with chick that it has killed. Genovesa Island, Galapagos.

Tui De Roy / Nazca booby (Sula granti), adult killing chick. Genovesa Island, Galapagos.

Tui De Roy / Nazca booby (Sula granti), two males fighting. Genovesa Island, Galapagos. Sequence 1/6.

Tui De Roy / Nazca booby (Sula granti), two males fighting. Genovesa Island, Galapagos. Sequence 2/6.

Tui De Roy / Nazca booby (Sula granti), male pinning another male down during fight. Genovesa Island, Galapagos. Sequence 3/6.

Tui De Roy / Nazca booby (Sula granti), male pinning another male down during fight. Genovesa Island, Galapagos. Sequence 4/6.

Tui De Roy / Nazca booby (Sula granti), two males resting during fight. Genovesa Island, Galapagos. Sequence 5/6.

Tui De Roy / Nazca booby (Sula granti), two males attacking each other after rest. Genovesa Island, Galapagos. Sequence 6/6.

Tui De Roy / Nazca booby (Sula granti), two fighting. Genovesa Island, Galapagos.

Tui De Roy / Nazca booby (Sula granti), two males in competition for onlooking female. Gardner Islet, Floreana Island, Galapagos.

Tui De Roy / Nazca booby (Sula granti), two males in competition for onlooking female. Gardner Islet, Floreana Island, Galapagos.

Tui De Roy / Nazca booby (Sula granti), two males in competition for onlooking female. Gardner Islet, Floreana Island, Galapagos.

Tui De Roy / Nazca booby (Sula granti), adult attacking chick. Genovesa Island, Galapagos.

Tui De Roy / Nazca booby (Sula granti), adult attacking chick. Genovesa Island, Galapagos.

Tui De Roy / Nazca booby (Sula granti), adult attacking chick. Genovesa Island, Galapagos.

Luke Massey / Giant river otters (Pteronura brasiliensis) fighting, Pantanal, Brazil.

Philippe Clement / Two Lynx (Lynx lynx) kittens play fighting in a forest in autumn, Bavarian Forest National Park, Germany, October. Captive.

David Tipling / Eurasian black vulture (Aegypius monachus) in aggressive posture approaching food and other vultures Sierra San Pedro, Extremadura, Spain. December

David Tipling / Eurasian black vulture (Aegypius monachus) in aggressive posture approaching food and other vultures Sierra San Pedro, Extremadura, Spain. December

David Tipling / Griffon (Gyps fulvus) and Black vultures (Coragyps atratus) fighting over food Sierra San Pedro, Extremadura, Spain. December

David Tipling / Eurasian black vulture (Aegypius monachus) in aggressive posture approaching food and other vultures Sierra San Pedro, Extremadura, Spain. December

David Tipling / Eurasian black vultures (Aegypius monachus) fighting, Sierra San Pedro, Extremadura, Spain. December

Piotr Naskrecki / Yellow-billed Stork (Mycteria ibis) pair fighting, Gorongosa National Park, Mozambique

Duncan Usher / Ring-necked Pheasant (Phasianus colchicus) males in territorial fight, Texel, Netherlands

Duncan Usher / Ring-necked Pheasant (Phasianus colchicus) males in territorial fight, Texel, Netherlands

Duncan Usher / Ring-necked Pheasant (Phasianus colchicus) males in territorial fight, Texel, Netherlands

Duncan Usher / Ring-necked Pheasant (Phasianus colchicus) males in territorial fight, Texel, Netherlands

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

David Tipling / Hooded crows (Corvus cornix) fighting, Hortobagy National Park, Hungary January

David Tipling / Hooded crow (Corvus cornix) fighting Hortobagy National Park, Hungary January

David Tipling / Pied avocet (Recurvirostra avosetta) courtship ritual immediately after copulation, North Norfolk, England, UK. May

David Tipling / Pied avocet (Recurvirostra avosetta) territorial dispute between pairs on island used for nesting North Norfolk, England, UK. May

David Tipling / Pied avocet (Recurvirostra avosetta) North Norfolk, England, UK. May

Sandesh Kadur / Pair of Glowing pufflegs (Eriocnemis vestita) chasing away a Long-tailed sylph (Aglaiocercus kingii), Ecuador.

Juan Carlos Munoz / Iberian ibex (Capra pyrenaica) on rocky clifftop, two headbutting one another. Maro-Cerro Gordo Cliffs Natural Area, Granada, Andalusia, Spain. January 2018.

Tim Fitzharris / Northern Elephant Seal (Mirounga angustirostris) bulls fighting in surf, Piedras Blancas, California

Giri Cavale / Leopard (Panthera pardus) male chasing away a melanistic leopard / black panther, Nagarahole National Park, Nilgiri Biosphere Reserve, Karnataka, India.

David Perpinan / Two male Black grouse (Tetrao tetrix) fighting at lek, Cairngorms, Scotland, UK, UK, April.

David Perpinan / Two male Black grouse (Tetrao tetrix) fighting at a lek, Cairngorms, Scotland, UK, April.

David Perpinan / Three male Black grouse (Tetrao tetrix) at a lek, Cairngorms, Scotland, UK, April.

David Perpinan / Blue-fronted amazon parrots (Amazona aestiva) fighting in a tree, Pantanal, Mato Grosso do Sul, Brazil.

David Perpinan / Blue-fronted amazon parrots (Amazona aestiva) fighting at roost site, Pantanal, Mato Grosso do Sul, Brazil.

David Perpinan / Two Chaco chachalacas (Ortalis canicollis) fighting, Pantanal, Mato Grosso do Sul, Brazil.

David Perpinan / Two Chaco chachalacas (Ortalis canicollis) fighting, Pantanal, Mato Grosso do Sul, Brazil.

Jeff Vanuga / Common eider duck (Somateria mollissima) female defending nest against Glaucous gull (Larus hyperboreus) in Spitsbergen, Svalbard, Norway. June.

Luke Massey / Hyacinth macaws (Anodorhynchus hyacinthinus) fight in palm tree, Pantanal, Brazil.

Luke Massey / Hyacinth macaws (Anodorhynchus hyacinthinus) fight in palm tree, Pantanal, Brazil.

Luke Massey / Crested caracaras (Caracara cheriway) fighting over food Pantanal, Brazil..

Magnus Lundgren / Wild Wonders of China / Temminck's tragopans (Tragopan temminckii ) males fighting on a stone near a waterfall, Tangjiahe National Nature Reserve, Sichuan Province, China

Magnus Lundgren / Wild Wonders of China / Temminck's tragopans (Tragopan temminckii ) males fighting on a stone near a waterfall, Tangjiahe National Nature Reserve, Sichuan Province, China

Magnus Lundgren / Wild Wonders of China / Temminck's tragopans (Tragopan temminckii ) males fighting on a stone near a waterfall, Tangjiahe National Nature Reserve, Sichuan Province, China

Karine Aigner / African wild dog (Lycaon Pictus) chasing a pack member to steal it's prey. Zimbabwe.

Karine Aigner / Cheetah (Acinonyx jubatus) trying to fight off a pack of African wild dogs (Lycaon Pictus) from stealing Impala prey in Linyanti Wildlife Reserve, Botswana.

Karine Aigner / African wild dogs (lycaon pictus) fighting with a Spotted hyena (Crocuta crocuta) Malilangwe Wildlife Reserve. Zimbabwe.

Karine Aigner / African wild dogs (Lycaon pictus) five attack a Cheetah (Acinonyx jubatus) defending its Impala kill. Linyanti Wildlife Reserve, Botswana.

Remi Masson / Group of Wels catfish (Silurus glanis) fighting, River Ebro, Spain, April.

Valeriy Maleev / Altai argali sheep (Ovis ammon ammon) males fighting, Altai Mountains, Mongolia. October.

Remi Masson / Male Zander (Sander lucioperca) protecting eggs in nest, attacks camera, Rhone-Alpes, France, April.

Felis Images / Lesser fish eagle (Icthyophaga humilis) two fighting in flight, Jim Corbett National Park, Uttarakhand, India. Small repro only.

Remi Masson / Two Wels catfish (Silurus glanis) fighting, River Ebro, Spain, April.

Remi Masson / Male Common toads (Bufo bufo) fighting underwater during mating season, Ain, Rhone-Alps, France, March.

Ashley Cooper / Antarctic Fur Seal (Arctocephalus gazella) bull, showing a threat display. Salisbury Plain, South Georgia, Southern Ocean, February.

Ashley Cooper / Warning sign about the presence of Argentinian mines on the Falkands, February 2014.

Ashley Cooper / Warning sign about the presence of Argentinian mines on the Falkands, February 2014.

Tony Heald / Southern elephant seal (Mirounga leonina), two males fighting. Gold Harbour, South Georgia. October.

Tony Heald / Southern elephant seal (Mirounga leonina), two males threatening, pre-fight. Gold Harbour, South Georgia. October.

Tony Heald / Southern elephant seal (Mirounga leonina), male rearing up in threatening posture. Gold Harbour, South Georgia. October.

Tony Heald / Southern elephant seal (Mirounga leonina), two males fighting with female in forground, Gold Harbour, South Georgia. October 2017.

Tony Heald / Southern elephant seal (Mirounga leonina), male rearing up in threatening posture. Gold Harbour, South Georgia. October.

Tony Heald / Southern elephant seal (Mirounga leonina), two males fighting. Gold Harbour, South Georgia. October.

Tony Heald / Southern elephant seal (Mirounga leonina), two males fighting. Gold Harbour, South Georgia. October.

Tony Heald / Southern elephant seal (Mirounga leonina), two males threatening one another, about to fight. Gold Harbour, South Georgia. October 2017.

Tony Heald / Northern giant petrel (Macronectes halli) running with wings outstretched, face bloodied. St Andrews Bay, South Georgia. October.

Tony Heald / Northern giant petrel (Macronectes halli) running in aggression with bloodied face. St Andrews Bay, South Georgia. October

Tony Heald / Northern giant petrel (Macronectes halli) running with bloodied beak, King penguins (Aptenodytes patagonicus) in background. St Andrews Bay, South Georgia. September.

Tony Heald / Southern giant petrel (Macronectes giganteus) fighting with Northern giant Petrel (Macronectes halli). Southern elephant seal (Mirounga leonina) male observing in background. St Andrews Bay, South Ge...

Tony Heald / Southern giant petrel (Macronectes giganteus) and Northern giant Petrel (Macronectes halli) fighting with beaks raised upwards. Southern elephant seal (Mirounga leonina) male observing in background....

Tony Heald / Brown skua (Stercorarius antarcticus), two fighting over carrion whilst standing in sea. South Georgia. September.

Tony Heald / Southern elephant seal (Mirounga leonina), two males fighting. Gold Harbour, South Georgia. October.

Tony Heald / Southern elephant seal (Mirounga leonina), male rearing up aggressively with King penguins (Aptenodytes patagonicus) in background. St Andrews Bay, South Georgia. October.

Tony Heald / Southern elephant seal (Mirounga leonina), two males fighting. St Andrews Bay, South Georgia. October.

Tony Heald / Leopard seal (Hydrurga leptonyx) and Southern elephant seal (Mirounga leonina) male, threatening each other. St Andrews Bay, South Georgia. October.

Tony Heald / Leopard seal (Hydrurga leptonyx) and Southern elephant seal (Mirounga leonina) male, threatening each other. St Andrews Bay, South Georgia. October.