Tony Heald / Hippopotamus {Hippopotamus amphibius} territorial defense at water edge, Chobe national park, Botswana.

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

Marie Read / Wood Ducks (Aix sponsa), females behave aggressively toward a male (second from right) that is trying to join them on a floating log, autumn, New York, USA, October.

Matthew Maran / Red Fox (Vulpes Vulpes) patrolling the allotment North London, England, UK, September.

Andy Rouse / Bengal tiger (Panthera tigris) tigress Arrowhead sniffing tree for scent, Ranthambhore, India

David Gallan / Spotted-tailed quoll (Dasyurus maculatus) scent marking in Monga National Park, New South Wales, Australia. Remote camera, triggered by movement. Highly Commended 2018 Wildlife Photographer Of The Yea...

Klein & Hubert / Hippopotamus (Hippopotamus amphibius) charging in Luangwa river, close up of mouth and teeth, Zambia

Philippe Clement / Territorial Common raven (Corvus corax) on cliff top, tearing out vegetation, Eshaness, Northmavine, Shetland Islands, Scotland, UK, May.

Dave Bevan / Male Pied flycatcher (Ficedula hypoleuca) calling to establish territory and attract a mate, Carmarthenshire, Wales, UK, May.

Giri Cavale / Melanistic leopard / Black panther (Panthera pardus) on territorial patrol on track, Nagarahole National Park, Nilgiri Biosphere Reserve, Karnataka, India.

Jordi Chias / Two male Dusky groupers (Epinephelus marginatus) fighting for territory during mating season at 'baixa do meros', a small pinnacle at Formigas islets Protected area, near Santa Maria Island, Azores. F...

Jim Manthorpe / Close-up of a Common otter (Lutra lutra) grooming and rolling in seaweed, Western Scotland. March.

Fred Olivier / Chinstrap penguin (Pygoscelis antarcticus) adding a stick to its nest and fighting with a neighbouring pair, Aitcho Island, South Shetland Islands.

Krijn Trimbos / Great crested grebe (Podiceps cristatus) with head low to the water in aggressive display, The Netherlands. March.

Krijn Trimbos / Great crested grebe (Podiceps cristatus) two in territorial fight, The Netherlands, March.

Krijn Trimbos / Great crested grebe (Podiceps cristatus) two in territorial fight, The Netherlands, March.

Krijn Trimbos / Great crested grebe (Podiceps cristatus) two in territorial fight, The Netherlands, March.

David Pattyn / Great crested grebe (Podiceps cristatus) attacking another grebe in the mating season during a territorial dispute. The Netherlands. April.

David Pattyn / Great crested grebe (Podiceps cristatus) in a threathening posture trying to intimidate another grebe in a territorial dispute. Head low over the water and crest erected. The Netherlands. April.

David Pattyn / Great crested grebe (Podiceps cristatus) in a threathening posture trying to intimidate another grebe in a territorial dispute. Head low over the water and crest erected. The Netherlands. March 2013

David Pattyn / Great crested grebe (Podiceps cristatus) in a threathening posture trying to intimidate another grebe in a territorial dispute. The Netherlands. April 2014

David Pattyn / Great crested grebe (Podiceps cristatus) adults fighting in a territorial dispute in the mating season. The Netherlands.april 2014

David Pattyn / Great crested grebe (Podiceps cristatus) in a threathening posture trying to intimidate another grebe in a territorial dispute. The Netherlands. April.

David Pattyn / Great crested grebe (Podiceps cristatus) in a threathening posture trying to intimidate another grebe in a territorial dispute. Head low over the water and crest erected. The Netherlands. April.

John & Mary-Lou Aitchison / Female European otter (Lutra lutra) on a rock grooming her cub before rolling over and scent marking, Scotland, UK, November.

Nick Garbutt / Male Bengal tiger (Panthera tigris tigris) known as 'Sundar' (B2) patrolling territory, Bandhavgarh National Park, Madhya Pradesh, India. Endangered species.

Pål Hermansen,Pal Hermansen / Nuthatch (Sitta europaea) chasing away and Black tit (Periparus ater) in car graveyard, Varmland, Sweden, December

Tui De Roy / Stewart Island Brown Kiwi or Southern Tokoeka (Apteryx australis lawryi), female probing by scent for sand hoppers in rotting kelp beach wrack at night, Ocean Beach, Stewart Island, New Zealand

Nick Upton / European robin (Erithacus rubecula) standing upright in a territorial threat display in a meadow among patchy snow, Wiltshire, UK, January.

Shattil & Rozinski,Shattil & Rozinski / Black bear (Ursus americanus) cub climbing a fence, Minnesota, USA, May.

Denis-Huot,Denis-Huot / Lion (Panthera leo) males feeding on buffalo (Syncerus caffer) with other buffalos watching. Masai Mara, Kenya, Vulnerable species.

Denis-Huot,Denis-Huot / Lion (Panthera leo) male chasing White backed vultures (Gyps africanus) off its prey, Masai-Mara Game Reserve, Kenya. Vulnerable species.

Igor Shpilenok,Igor Shpilenok / Red Foxes (Vulpes vulpes) fighting outside ranger cabin window. Kronotsky Zapovednik Nature Reserve, Kamchatka Peninsula, Russian Far East, February.

Denis-Huot / African Buffalo (Syncerus caffer) males fighting, Nakuru National park, Kenya

Andy Trowbridge / Great Tit (Parus major) perched on frost covered spruce branch with wings open in a show of aggression. Southern Norway, October.

Paul Hobson / Arctic tern (Sterna paradisaea) two fighting in the air, Scotland, UK July

Anup Shah / Topi (Damaliscus lunatus jimela) two males sparring, with another approaching, Masai Mara National Reserve, Kenya. March

Markus Varesvuo / Ruff (Philomachus pugnax) two males displaying in territorial dispute, Liminka Finland June

Anup Shah / Western lowland gorilla (Gorilla gorilla gorilla) dominant male silverback 'Makumba' aged 32 years walking at the edge of the forest, Bai Hokou, Dzanga Sangha Special Dense Forest Reserve, Central Afr...

Anup Shah / Western lowland gorilla (Gorilla gorilla gorilla) rear view of dominant male silverback 'Makumba' aged 32 years walking along a forest trail, Bai Hokou, Dzanga Sangha Special Dense Forest Reserve, Cen...

David Pattyn / Red foxes (Vulpes vulpes) two fighting, probably over territory, The Netherlands, August

David Pattyn / Alpine ibex (Capra ibex) adult male chasing two young males away, Gran Paradiso National Park, Italy, July

David Pattyn / Red necked grebe (Podiceps grisegena) approaching a competitor in an attempt to drive him away during the courting season, Danube area, Bulgaria, April

Juan Carlos Munoz / Great Egrets (Ardea alba) territorial fight above nest colony, Everglades National Park, Florida, USA, February.

Juan Carlos Munoz / Great Egrets (Ardea alba) territorial dispute above nest colony, Everglades National Park, Florida, USA, February.

Tui De Roy / Galapagos fur seal (Arctocephalus galapagoensis) large territorial bull on volcanic rocks. South Coast Cerro Azul (Cinco Cerros), Isabela, Galapagos Islands, Ecuador, June.

Andy Rouse / Agile wallabies (Macropus agilis) sparring and fighting, Bamarru Plains, Northern Territories, Australia