Morley Read / Slow motion clip of a group of male Mallards (Anas platyrhynchos) competing violently to mate with a single female, Cornwall, England, UK, May 2018.

Morley Read / Slow motion clip of a male Orchid bee (Euglossini) gathering nectar from an orchid (Lycomormium ecuadorense) flower, Imbabura Province, Ecuador.

Alex Mustard / Yellowtail tang (Zebrasoma xanthurum) male and female turn belly to belly during spawning to ensure fertilization. Temple, Ras Umm Sid, Sharm El Sheikh, Sinai, Egypt. Red Sea. This action is very fast...

Chase Dekker / African Lion (Panthera leo) male, Masai Mara, Kenya

Gerry Ellis / Western Lowland Gorilla (Gorilla gorilla gorilla) silverback, Limbe Wildlife Centre, Cameroon

Jami Tarris / Walrus (Odobenus rosmarus) bull, Spitsbergen, Svalbard, Norway

Juergen & Christine Sohns / African Lion (Panthera leo) male drinking at waterhole, Tswalu Game Reserve, South Africa

Juergen & Christine Sohns / African Lion (Panthera leo) male, Tswalu Game Reserve, South Africa

Juergen & Christine Sohns / African Lion (Panthera leo) juvenile male, Mountain Zebra National Park, South Africa

Anup Shah / Olive Baboon (Papio anubis) male with three month old young, Gombe National Park, Tanzania

Anup Shah / Eastern Chimpanzee (Pan troglodytes schweinfurthii) fourteen year old sub-adult male, named Fundi, making submissive facial gesture, Gombe National Park, Tanzania

Anup Shah / Eastern Chimpanzee (Pan troglodytes schweinfurthii) four year old infant male, named Gizmo, foraging for insects in log, Gombe National Park, Tanzania

Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) twenty year old male, named Titan, Gombe National Park, Tanzania

Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) seven year old juvenile male, named Siri, feeding on vines, Gombe National Park, Tanzania

Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) four year old infant male, named Gizmo, Gombe National Park, Tanzania

Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) eighteen year old male, named Sampson, Gombe National Park, Tanzania

Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) four year old infant male, named Gizmo, Gombe National Park, Tanzania

Richard Du Toit / Greater Double-collared Sunbird (Nectarinia afra) male on Pincushion (Leucospermum sp) flower, Western Cape, South Africa

Martin Willis / Victoria's Riflebird (Ptiloris victoriae) male in courtship display, Atherton Tableland, Queensland, Australia. Sequence 2 of 3

Martin Willis / Splendid Fairywren (Malurus splendens) female and male, Queensland, Australia

Martin Willis / Rainbow Lorikeet (Trichoglossus haematodus) pair preening during courtship, Magnetic Island, Queensland, Australia

Martin Willis / Budgerigar (Melopsittacus undulatus) father with begging chick at nest cavity, Queensland, Australia

Danny Green / Polar bear (Ursus maritimus) male standing beside rocks in frozen and snow covered landscape. Svalbard, Norway, April 2019.

Danny Green / Polar bear (Ursus maritimus) male walking across frozen landscape. Svalbard, Norway, April 2019.

Danny Green / Polar bear (Ursus maritimus) male in snow. Svalbard, Norway, April.

Danny Green / Polar bear (Ursus maritimus), male and female approaching each other across snow covered rocky landscape. Svalbard, Norway, April 2019.

Danny Green / Polar bear (Ursus maritimus) male approaching female on snow covered hill top. Svalbard, Norway, April 2019.

Danny Green / Polar bear (Ursus maritimus) male approaching female in rocky area covered in snow. Svalbard, Norway, April 2019.

Danny Green / RF - Polar bear (Ursus maritimus) male walking through snow covered landscape, mountains in background. Svalbard, Norway, April (This image may be licensed either as rights managed or royalty free.)

Danny Green / Polar bear (Ursus maritimus) male female pair looking upwards, snow covered hills in background. Svalbard, Norway, April 2018.

Phil Savoie / Painted nomad bee (Nomada fucata) male bee with characteristic green eyes, sleeping with jaws locked around grass stem, Monmouthshire, Wales, UK. June

Phil Savoie / Grey patched mining bee (Andrena nitida),male feeding rambling rose flower (Rosa sp) Monmouthshire, Wales, UK. April

Nick Garbutt / Puma (Puma concolor puma) young male standing with mouth open. Estancia Amarga, near Torres del Paine National Park, Patagonia, Chile. December.

John Cancalosi / Sonoran desert toad (Incilius alvarius) pair mating, with trail of spawn in water. Arizona, USA.

Alex Mustard / Dugong (Dugong dugon) male and juvenile Golden trevally (Gnathanodon speciosus) swimming over Seagrass (Halophila stipulacea) meadow. Marsa Nabaa, Marsa Alam, Egypt.

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.

Tony Wu / Humpback whale (Megaptera novaeangliae australis) male calf playing at ocean surface after coming up to breathe. Vava'u Islands, Tonga.

Andy Rouse / Bengal tiger (Panthera tigris) male, sub-adult aged three years, face portrait. Ranthambhore National Park, India.

Gary Bell/ Oceanwide / Australian Giant Cuttlefish (Sepia apama) group gathered for mating, Whyalla, South Australia, Australia

Gary Bell/ Oceanwide / Australian Giant Cuttlefish (Sepia apama) male and female, Whyalla, South Australia, Australia

Gary Bell/ Oceanwide / Australian Giant Cuttlefish (Sepia apama) males fighting over female, Whyalla, South Australia, Australia

Gary Bell/ Oceanwide / Australian Giant Cuttlefish (Sepia apama) males fighting over female, Whyalla, South Australia, Australia

Gary Bell/ Oceanwide / Variegated Jawfish (Opistognathus solorensis) male brooding eggs in mouth, Anilao, Philippines

Gary Bell/ Oceanwide / Variegated Jawfish (Opistognathus solorensis) male brooding eggs in mouth, Anilao, Philippines

Piotr Naskrecki / Termite (Macrotermes mossambicus) winged individual on pile of wings shed by other termites, with winged male Carpenter ants (Camponotus). Gorongosa National Park, Mozambique. Highly commended in the...

Ingo Arndt / Mountain Lion (Puma concolor) hunting Guanaco (Lama guanicoe) male, Torres del Paine National Park, Patagonia, Chile, sequence 3 of 12. Joint winner of the Mammal Behaviour Category of the Wildlife Ph...

Stefan Christmann / Emperor penguin (Aptenodytes forsteri) colony, males huddling whilst incubating eggs. Atka Bay, Antarctica. July. Winner of the Portfolio category of the Wildlife Photographer of the Year Awards 2019.

Oscar Dewhurst / Fallow deer (Dama dama) walking across frost-covered playing fields at dawn, with tower blocks of London in the background. Richmond Park, London, UK. December

Oscar Dewhurst / Red deer (Cervus elaphus) stag roaring, silhouetted under trees at sunrise. Bushy Park, London, UK. September

Jack Dykinga / Bighorm sheep (Ovis canadensis) males grouped together before the rutting season. Valley of Fire State Park, Nevada, USA, February.

Mark Raycroft / Woodland Caribou (Rangifer tarandus caribou) male, Newfoundland, Canada

Mark Raycroft / Moose (Alces alces) bull browsing, North America

Matthew Maran / Red fox (Vulpes vulpes) dog interacting with a vixen in an urban garden. North London, UK. June.

Matthew Maran / Red fox (Vulpes vulpes) dog interacting with a vixen in an urban garden. North London, UK. July.

Matthew Maran / Red fox (Vulpes vulpes) cub defending its kill,a large Brown rat (Rattus norvegicus) from another cub, North London, UK. August. Highly commended in the Behaviour : Mammals Category of the Wildlife Ph...

Alex Mustard / School of White collar butterflyfish (Chaetodon collare) pack together above a coral reef. North Male Atoll, Maldives. Indian Ocean

Alex Mustard / Pair of Western clown anemonefish (Amphiprion ocellaris) spawning orange eggs on the rock beneath their Magnificent sea anemone (Heteractis magnifica) home on a coral reef. This photo shows the larger...

Robert Valentic / Heath Monitor (Varanus rosenbergi) male enacting a threat display, in mallee/heath habitat near Pinnaroo, South Australia.

Loic Poidevin / Eurasian bullfinch (Pyrrhula pyrrhula) male on a branch feeding on Rowan (Sorbus aucuparia) berries, Leon, Spain, February.

Loic Poidevin / Eurasian bullfinch (Pyrrhula pyrrhula) male on a branch feeding on Rowan (Sorbus aucuparia) berries, Leon, Spain, February.

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...

Alex Mustard / RF - Portrait of Coral hermit crab (Paguritta harmsi) living in a hard coral colony. North Male Atoll, Maldives. Indian Ocean (This image may be licensed either as rights managed or royalty free.)

Alex Mustard / RF - A school of Crescent-tail bigeye (Priacanthus hamrur) on a coral reef. North Male Atoll, Maldives. Indian Ocean (This image may be licensed either as rights managed or royalty free.)

Alex Mustard / Portrait of a male short snouted seahorse (Hippocampus hippocampus) in sea oak seaweed (Halidrys siliquosa). Devon, England, United Kingdom. British Isles. English Channel. North East Atlantic Ocean.

Nick Upton / Male Thick-legged flower beetle (Oedemera nobilis), with a Pyramidal orchid (Anacamptis pyramidalis) pollinium attached to its head, nectaring on Common hogweed flowers (Heracleum sphondylium), Wiltsh...

Oriol Alamany / Snow leopard (Panthera uncia) male in snow, in Spiti Valley, Cold Desert Biosphere Reserve, Himalaya, Himachal Pradesh, India, March

Ernie Janes / Black howler (Alouatta caraya) male and female, captive, occurs in Brazil and Paraguay. With digitally added leaf pattern.

Ralph Pace / Shortfin Mako (Isurus oxyrhynchus) male caught on fishing line, California

John Shaw / Great frigatebird (Phaethon aethereus) male at nest site, with gular sac inflated to attract females. Genovesa Island, Galapagos, May.

Espen Bergersen / Killer whale / orca (Orcinus orca) male. Kvaloya, Troms, Norway October

Andy Rouse / Stonechat, (Saxicola rubicola) male shaking head, blurred motion. UK

Andy Rouse / Alcedo volcano Galapagos giant tortoise (Chelonoidis vandenburghi) adult male on forest track, Urbina Bay, Isabela Island, Galapagos.

Andy Rouse / African lion, (Panthera leo), male, Masai Mara, Kenya, Africa,

Andy Rouse / Kingfisher, (Alcedo atthis), diving for fish, UK

Andy Rouse / Kingfisher, (Alcedo atthis), diving for fish, UK

Andy Rouse / Kingfisher, (Alcedo atthis), diving for fish, UK

Edwin Giesbers / Seven spot ladybird (Coccinella septempunctata) pair mating on Mayweed (Anthemis sp) flower. Cyprus. April.

Edwin Giesbers / Seven spot ladybird (Coccinella septempunctata) pair mating on Mayweed (Anthemis sp) flower. Cyprus. April.

Winfried Wisniewski / African Lion (Panthera leo) male, Masai Mara, Kenya

Winfried Wisniewski / African Lion (Panthera leo) males nuzzling, Masai Mara, Kenya

Doc White / Sea Otter, (Enhydra lutris), young male, Elkhorn Slough, California, USA. January

Ben Gillett / Slow motion clip of a female Appaloosa horse grooming a male, Bristol, England, UK, May.

John Chan / Two male Southern Pacific rattlesnakes (Crotalus oreganus helleri) fighting during mating season. This behaviour is known as a "combat dance", and is used to determine dominance and the right to mate...

Yashpal Rathore / Bengal tiger (Panthera tigris tigris) walking at night, with monsoon clouds and lightning. Kanha National Park, Central India. Dominant male (T29)

Yashpal Rathore / Bengal tiger (Panthera tigris tigris) dominant male (T29) cooling off in a waterhole Kanha National Park, Central India. Camera trap image.

Yashpal Rathore / Bengal tiger (Panthera tigris tigris) dominant male (T29) cooling off in a waterhole Kanha National Park, Central India. Camera trap image.

Yashpal Rathore / Bengal tiger (Panthera tigris tigris) dominant male (T29) and resident female (T27) cooling off in a watering hole Kanha National Park, Central India. Camera trap image.

Yashpal Rathore / Bengal tiger (Panthera tigris tigris) dominant male (T29) and resident female (T27) cooling off in a waterhole Kanha National Park, Central India. Camera trap image.

Yashpal Rathore / Bengal tiger (Panthera tigris tigris) female (T27) acting cautiously as dominant male (T29) approaches watering hole Kanha National Park, Central India. Camera trap image.

Yashpal Rathore / Bengal tiger (Panthera tigris tigris) dominant male (T29) walking on mud dam wall. Kanha National Park, Central India. Camera trap image.

Doug Gimesy / Researcher examining the spur of a platypus (Ornithorhynchus anatinus) that was captured as part of a Melbourne Water study into their distribution. Spurs can help a researchers age a male platypus. W...

Doug Gimesy / Researcher examining the spur of a Platypus (Ornithorhynchus anatinus) that was captured as part of a Melbourne Water study into their distribution. Spurs can help a researchers age a male platypus. W...