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. (non-ex)

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...

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

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

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

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 / 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...

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

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.

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.

Espen Bergersen / Aerial shot of Killer whales (Orcinus orca) near the surface, showing mating behaviour, Troms, Norway, August.

Terry Whittaker / Mandarin duck (Aix galericulata) male female pair, Reddish Vale Country Park, Greater Manchester, UK. December

Neil Aldridge / White rhinoceros (Ceratotherium simum) male and female, face to face, Mosi Oa Tunya National Park, Zambia.

Ross Hoddinott / Common blue butterflies (Polyommatus icarus) basking in the morning light, Vealand Farm, Devon, UK. July

Marie Read / Western Grebe (Aechmorphus occidentalis), pair during 'rushing' courtship display in which they run across water's surface in synchrony, near Escondido, California, USA, January.

Marie Read / Black-necked stilts (Himantopus mexicanus) pair performing post-copulatory display (as copulation ends, the male slides off the female leaving his wings draped over her and crossing his bill with hers...

David Gallan / Male Satin bowerbird (Ptilonorhynchus violaceus) courting female on suburban street verge, bower filled with blue plastic, Australia, October 2018.

Eric Baccega / Lioness (Panthera leo), aggressively rebuffing male lion banks of the Luangwa river, South Luangwa National Park, Zambia

Nick Upton / Pair of White storks (Ciconia ciconia) mating on their nest, Knepp Castle Estate, Sussex, England, UK, April. This is the first recorded instance of White storks nesting in the UK for several hundreds...

Nick Upton / Pair of White storks (Ciconia ciconia) arranging nest material on their nest, Knepp Castle Estate, Sussex, England, UK, April. This is the first recorded instance of White storks nesting in the UK for...

Nick Upton / Pair of White storks (Ciconia ciconia) arranging nest material on their nest, Knepp Castle Estate, Sussex, England, UK, April. This is the first recorded instance of White storks nesting in the UK for...

John Chan / Male California least tern (Sternula antillarum browni) presenting fish offering to female during mating, Huntington Beach, California, USA, May.

Michael Hutchinson / Pair of Marsh fritillary butterflies (Euphydryas aurinia) courting on a Buttercup (Ranunculus), Devon, England, UK, June.

Michael Hutchinson / Pair of Marsh fritillary butterflies (Euphydryas aurinia) courting on a Buttercup (Ranunculus), Devon, England, UK, June.

Michael Hutchinson / Pair of Marsh fritillary butterflies (Euphydryas aurinia) mating, Devon, England, UK, June.

Michael Hutchinson / Close-up of a pair of Marsh fritillary butterflies (Euphydryas aurinia) mating, showing tips of abdomens, Devon, England, UK, June.

Michael Hutchinson / Close-up of a pair of Marsh fritillary butterflies (Euphydryas aurinia) mating, shot tilt downs, Devon, England, UK, June.

Michael Hutchinson / Male Marsh fritillary butterfly (Euphydryas aurinia) displaying to a female on a Buttercup (Ranunculus) flower, Devon, England, UK, June.

Nick Upton / White stork (Ciconia ciconia) pair mating on their nest at sunset, Knepp estate, Sussex, UK, April 2019. This is the first recorded instance of White storks nesting in the UK for several hundreds of y...

Nick Upton / White stork (Ciconia ciconia) pair performing an up-down display with bill clattering on their nest in an Oak tree, Knepp estate, Sussex, UK, April 2019. This is the first recorded instance of White s...

Nick Upton / White stork (Ciconia ciconia) male landing with nest material and joining his mate on their nest in an Oak tree at sunset, Knepp estate, Sussex, UK, April 2019. This is the first recorded instance of...

Stefan Christmann / Emperor penguin (Aptenodytes forsteri) pair transferring recently laid egg from female to male. Atka Bay, Antarctica. June.

Stefan Christmann / Emperor penguin (Aptenodytes forsteri) pair with recently laid egg, on sea ice. Atka Bay, Antarctica. May.

Stefan Christmann / Emperor penguin (Aptenodytes forsteri), pair mating. Atka Bay, Antarctica. May.

Stefan Christmann / Emperor penguin (Aptenodytes forsteri) pair practising incubating with a snowball. Atka Bay, Antarctica. May.

Stefan Christmann / Emperor penguin (Aptenodytes forsteri) pair practising incubating with a snowball. Atka Bay, Antarctica. May. Winner of the Polar Passion Category of the Nature's Best Photography Competition 2019.

Stefan Christmann / Emperor penguin (Aptenodytes forsteri) pair in courtship, on sea ice. Atka Bay, Antarctica. May.

Stefan Christmann / Emperor penguin (Aptenodytes forsteri) pair, female laying egg. Atka Bay, Antarctica. June.

Stefan Christmann / Emperor penguin (Aptenodytes forsteri), pair transferring recently laid egg from female to male. Atka Bay, Antarctica. June. Sequence 2/2.

Stefan Christmann / Emperor penguin (Aptenodytes forsteri) pair mating. Atka Bay, Antarctica. May. Sequence 3/4.

Stefan Christmann / Emperor penguin (Aptenodytes forsteri) pair mating on sea ice. Atka Bay, Antarctica. May.

Sven Zacek / Ural owl (Strix uralensis) female on nest, male landing with twig in beak. Tartumaa, Southern Estonia. April.

Sven Zacek / Ural owl (Strix uralensis) male presenting prey to nesting mate. Tartumaa, Southern Estonia. April.

Sven Zacek / Ural owl (Strix uralensis) female feeding at nest on rodent prey presented by mate. Tartumaa, Southern Estonia. April.

John Cancalosi / American toads (Anaxyrus americanus), several males competing to mate with female, Maryland, USA, April.

Donald M. Jones / American Avocet (Recurvirostra americana) pair courting, Montana

Shane Gross / Nurse sharks (Ginglymostoma cirratum) two in a courtship dance at sunrise in a mangrove area near Eleuthera, Bahamas.

Steven David Miller / Red-collared lorikeet (Trichoglossus rubritorquis) pair examining hole in Eucalyptus as a potential nesting hollow. Katherine, Northern Territory, Australia.

David Fleetham / Clark's anemonefish (Amphiprion clarkii), pair tending to egg mass placed beside the protection of an anemone. Yap, Micronesia.

Tui De Roy / Alcedo giant tortoise (Chelonoidis vandenburghi) pair mating in shallow pool, with two others resting nearby. Alcedo Volcano, Isabela Island, Galapagos

Tui De Roy / Blue-footed booby (Sula nebouxii), pair in courtship display. Punta Pitt, San Cristobal Island, Galapagos. April 2017.

Tui De Roy / Red-footed booby (Sula sula), pair nest building in tree. Darwin Bay, Genovesa Island, Galapagos.

Philippe Clement / Pair of Roe deer (Capreolus capreolus) resting and grazing in forest in summer, France, September.

Philippe Clement / Two Atlantic puffins (Fratercula arctica) in breeding plumage on cliff top, Sumburgh Head, Shetland Islands, Scotland, UK, June.

Philippe Clement / Great cormorant (Phalacrocorax carbo) bringing twig to nest in breeding colony, Belgium, March.

Dave Bevan / Slow motion clip of a pair of Common swifts (Apus apus) approaching and entering a nest hole in limestone cliff, Norfolk, England, UK, May.

Alex Mustard / Yellowtail tang (Zebrasoma xanthurum) male courting a female prior to spawning at dusk on a coral reef. Temple, Ras Umm Sid, Sharm El Sheikh, Sinai, Egypt. Red Sea.

Sandesh Kadur / Wide angle shot of a pair of Blue footed boobies (Sula nebouxii) displaying, Galapagos Islands, Ecuador.

Sandesh Kadur / Pair of Waved albatrosses (Phoebastria irrorata) displaying, tapping beaks, Galapagos Islands, Ecuador.

Remi Masson / Pair of Pumpkinseeds (Lepomis gibbosus) mating, male chasing other individuals away, River Rhone, Rhone-Alpes, France, June.

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

Konrad Wothe / Pair of European nuthatches (Sitta europaea) mating, Bavaria, Germany, April.

John Chan / Male California Least Tern (Sternula antillarum browni) courting a female, presenting a fish before chasing off another male, Huntington Beach, California, USA, May.

Chien Lee / Minden / Stick Insect (Monticomorpha flavolimbata) pair mating in mountains, Bengoh Range, Ecuador

Dave Bevan / Slow motion clip of two pairs of Jackdaws (Corvus monedula) squabbling over nest site, Worcestershire, England, UK, May.

John Waters / Wide-angle shot of a pair of Common European toads (Bufo bufo) in amplexus, jumping into a pond, Priddy, Somerset, England, UK, April.

Alex Mustard / Tawny nurse shark (Nebrius ferrugineus) group, individuals circling each other at dusk. Vavuu Atoll, Maldives. Indian Ocean.

Alex Mustard / Hawksbill turtle (Eretmochelys imbricata) pair circling each other above coral reef. Seven Mile Beach, Grand Cayman, Cayman Islands, British West Indies. Caribbean Sea.

David Pattyn / Diademed sifaka (Propithecus diadema diadema) pair, Maromizaha Reserve, Andasibe Mantadia area, eastern Madagascar. August.

Lucas Bustamante / Rio pescado harlequin toad (Atelopus balios) pair on branch, female on the left, Azuay, Ecuador, Critically endangered species, possibly extinct.

John Waters / Male Shoveler (Anas clypeata) chasing other males away from his mate, Greyale RSPB Reserve, Somerset Levels, England, UK, February.

Theo Bosboom / Edible frog (Pelophylax k. esculentus) catching a common blue damselfly (Enallagma cyathigerum) with its tongue with pair mating on stem above, Hondenven, Tubbergen, The Netherlands, July.

Theo Bosboom / Banded demoiselles (Calopteryx splendens) pair still clasped together after mating, with two males resting nearby, the Netherlands, July.

Theo Bosboom / Variable damselfly (Coenagrion pulchellum) pair mating, De Peel National Park, the Netherlands, July.

Philippe Clement / Pair of Black-tailed godwits (Limosa limosa) courting and mating in wetland, Belgium, April

Eric Medard / Female kestrel (Falco tunniculus) taking lizard prey gift from male, Mayenne, France

Tui De Roy / Volcan Alcedo Giant Tortoise (Chelonoidis nigra vandenburghi) pair mating, Alcedo Volcano, Isabela Island, Galapagos Islands, Ecuador

Tui De Roy / Magellanic Penguin (Spheniscus magellanicus) pair calling near chicks, Saunders Island, Falkland Islands

George Sanker / Mallard (Anas platyrhynchos) pair greeting on snow-covered pond. Acadia National Park, Maine, USA.

George Sanker / Mallard (Anas platyrhynchos)pair greeting on snow-covered pond. Acadia National Park, Maine, USA.

Konrad Wothe / Pair of Rosalia longicorns (Rosalia alpina) climbing up a Beech tree (Fagus sylvatica) whilst mating, Upper Bavaria, Germany, August.

Brian Bevan / Pair of Reed warblers (Acrocephalus scirpaceus) feeding young at nest, Bedfordshire, England, UK, July.

James Dunbar / Close-up of a pair of Nursery web spiders (Pisaura mirabilis) mating, UK. Captive.

Dave Bevan / Pair of Grey seals (Halichoerus grypus) mating on a beach, Norfolk, England, UK. December.

Dave Bevan / Pair of Grey seals (Halichoerus grypus) mating on a beach, Norfolk, England, UK. December.

Francisco Marquez / Pair of Iberian lynxes (Lynx pardinus) greeting, Andalusia, Spain, January.