Anup Shah / Maasai ostrich male and female courting (Struthio camelus massaicus) Masai Mara National Reserve, Kenya

Anup Shah / Black backed jackal (Canis mesomelas) male grooming female, Masai Mara National Reserve, Kenya

Anup Shah / Lions mating (Panthera leo), Masai Mara National Reserve, Kenya

B&S Draker / Pipevine Swallowtail Butterflies (Battus philenor) pair mating close-up. Sinton, Corpus Christi, Coastal Bend, Texas, USA, June.

B&S Draker / Pipevine Swallowtail Butterfly (Battus philenor) pair mating. Sinton, Corpus Christi, Coastal Bend, Texas, USA, June.

Ross Hoddinott / 2020VISION / Common blue damselfly {Enallagma cyathigerum}, mating pair, Little Bradley Ponds, Devon, UK. July. 2020VISION Book Plate.

Ross Hoddinott / 2020VISION / Common blue damselfly {Enallagma cyathigerum}, mating pair, Little Bradley Ponds, Devon, UK. July

George Sanker / Yellow-bellied Marmots (Marmota flaviventris) mating. Yellowstone National Park, Wyoming, USA, June.

Patricio Robles Gil / Pale-legged Hornero (Furnarius leucopus) male and female birds building their mud nest on a branch. Parana, Southern Brazil.

Mark Hamblin / 2020VISION / Red-throated diver (Gavia stellata) adult pair displaying on breeding loch, Flow Country, Highland, Scotland, UK, June. Did you know? The Flow Country of Caithness and Sutherland is home to the larges...

Mark Hamblin / 2020VISION / Black grouse (Tetrao tetrix) female at lek on heather moorland with two males displaying nearby, Cairngorms NP, Grampian, Scotland, UK, April

Klaus Echle / Red Deer (Cervus elaphus) stag and two females in snow-covered woodlands. Black Forest, Germany, January.

Andy Rouse / Two Grizzly bears (Ursus arctos horribilis) male (right) and female fighting over salmon, Katmai NP, Alaska, USA, August

Andy Rouse / Two Grizzly bears (Ursus arctos horribilis) male (right) and female fighting over salmon, Katmai NP, Alaska, USA, August

Andy Rouse / African Lion (Panthera leo) male lion greeting female and cubs, Notch from Disney African Cats film, Masai Mara GR, Kenya, February

Jeff Wilson / Emperor penguin (Aptenodytes forsteri) two adults in colony, Cape Crozier, Antarctica, November 2009. Taken on location for BBC series, Frozen Planet, Spring.

Daniel Heuclin / Pyrenean mountain newt / brook salamander (Calotriton / Euproctus asper) mating pair, captive, from Pyreneen mountains, France and Spain, near threatened

Markus Varesvuo / Common Crossbill (Loxia curvirostra) male and female greeting, Kuusamo, Finland, February.

Solvin Zankl / Common european toad {Bufo bufo} two males attempting to mate with one female, Germany, March. Highly Commended, Other Animals category, GDT competition 2011

David Maitland / Close-up view of the upward-looking giant dorsal compound eyes of the St Marks fly (Bibio marci) used to detect female flies flying above. Like many insects the eyes are "hairy". Feltwell, Norfolk, UK...

David Maitland / Close-up view of the upward-looking giant dorsal compound eyes of the St Marks fly (Bibio marci) used to detect female flies flying above. Like many insects the eyes are "hairy". Feltwell, Norfolk, UK...

Terry Whittaker / 2020VISION / Great crested grebe (Podiceps cristatus) pair displaying on water at dawn, Rutland Water, Rutland, UK, April. Photographer quote: 'During the Rutland Water 2020VISION iWitness I was really struggling...

Niall Benvie / 2020VISION / Children from Lochinver primary school being shown how to plant trees on moorland at Culag Wood, Sutherland, Highlands, Scotland, UK, January 2011

Niall Benvie / 2020VISION / Children from Lochinver primary school planting trees on moorland at Culag Wood, Sutherland, Highlands, Scotland, UK, January 2011

Mark Hamblin / 2020VISION / Hen harrier (Circus cyaneus) female hovering over moorland, Glen Tanar Estate, Deeside, Scotland, UK, June. Photographer quote: "I'd been in the hide for over 5 hours when I heard the distant call of...

Markus Varesvuo / Velvet Scoter (Melanitta fusca) female (foreground) and male on water. Finland, May. Magic Moments book plate, page 150.

Juergen Freund / Green turtles (Chelonia mydas) mating over coral reef, Sipadan Island, Sabah, Malaysia, June, Endangered species

Ben Hall / 2020VISION / Irish Damselfly (Coenagrion lunulatum) pair mating, Montiagh's Moss, County Antrim, Northern Ireland, June. 2020VISION Book Plate.

Axel Gomille / Sloth Bear (Melursus ursinus) female with large cubs (on right) trying to fight off rogue male. Karnataka, India, March.

Diane McAllister / Great blue heron (Ardea herodias) landing with branch for its mate, who is constructing their nest on a treetop. Venice Rookery, Florida, USA, January

Andy Rouse / Mountain Gorilla (Gorilla beringei) male and female after mating. Rwanda, Africa

Juergen Freund / Coral trout / Leopard coral grouper (Plectropomus leopardus) mating behaviour. Males approach the females and display with their bodies and fins. Misool, Raja Ampat, West Papua, Indonesia,

Peter Cairns / 2020VISION / Mute swan (Cygnus olor) pair on water in winter dawn mist, Loch Insh, Cairngorms NP, Highlands, Scotland UK, December

Andy Rouse / Grizzly Bear (Ursus arctos horribilis) male (right) and female fighting in water over salmon. Katmai, Alaska, USA, August.

Andy Rouse / Grizzly Bear (Ursus arctos horribilis) male (right) and female fighting in water over salmon. Katmai, Alaska, USA, August.

Peter Cairns / 2020VISION / Pair of Gannets (Morus bassanus) mutual preening, Bass Rock, Firth of Forth, Scotland, UK, June

Peter Cairns / 2020VISION / Pair of Gannets (Morus bassanus) mutual preening, Bass Rock, Firth of Forth, Scotland, UK, June. Photographer quote: 'I never get tired of watching gannets. This pair who momentarily lined up in perfe...

Juergen Freund / Mating pair of Green turtles (Chelonia mydas) in the reef shallows. Sipadan Island, Sabah, Malaysia. June

Juergen Freund / Mating Green turtles (Chelonia mydas) in the reef shallows. Sipadan Island, Sabah, Malaysia, June

Juergen Freund / Split-level shot of mating pair of Green turtles (Chelonia mydas) in the reef shallows. Sipadan Island, Sabah, Malaysia, June

Juergen Freund / Split level shot of mating Green turtles (Chelonia mydas) in the reef shallows. Sipadan Island, Sabah, Malaysia, June

Kim Taylor / Drone / Hover Fly (Eristalis tenax) female against a white background. Surrey, UK, May.

Peter Cairns / 2020VISION / Mute swan (Cygnus olor) pair on water in winter dawn mist, Loch Insh, Cairngorms NP, Highlands, Scotland UK, December. 2020VISION Book Plate.

Anup Shah / African lion (Panthera leo) male following a female, courtship, Masai Mara National Reserve, Kenya. February

Edwin Giesbers / Breeding pair of White Stork (Ciconia ciconia) on nest. The Netherlands, April.

Edwin Giesbers / Five Mallard (Anas platyrhynchos) walking in a line across snow. Three males and two females. The Netherlands, January.

Sergey Gorshkov / Kamchatka brown bear (Ursus arctos beringianus) mating, Kamchatka, Far east Russia, May

Fergus Gill / Grey seal (Halichoerus grypus) couple fighting as the male (right) tries to mate with the female. Scotland, October .

Tim Laman / Satin Bowerbird (Ptilonorhynchus violaceus minor) male displays to a female who has entered his bower. This bower is decorated with all natural objects. Rainforest of the Atherton Tablelands, Queensl...

Konrad Wothe / European Bee-eater (Merops apiaster) presents prey item to potential mate, Bulgaria

Daniel Heuclin / Pair of Rainbow Grasshoppers (Dactylotum bicolor) mating. Arizona, USA. Controlled conditions.

Solvin Zankl / Pair of Common european toads (Bufo bufo) swimming together in pond, Germany

Solvin Zankl / Pair of Common european toads (Bufo bufo) with strings of toadspawn, in pond, Germany. Specially commended in Wildlife Photographer of the Year (WPOY) 2013, Underwater Worlds Category.

Anup Shah / African Lions (Panthera leo) male and female watching with irritation as a young cub aged 6-9 months approaches, Masai Mara National Reserve, Kenya. December

Nick Garbutt / A pair of Toco Toucans (Ramphastos toco) flying across the Piquiri River at dawn, northern Pantanal, Mato Grosso, Brazil, September. (Digitally Modified)

David Tipling / European brown hare (Lepus europaeus) boxing in spring. Norfolk, UK, March

Roger Powell / Ruff (Philomachus pugnax) male displaying to attract the attention of a Reeve (female) nearby, Varanger plateau, Arctic Norway. June

Laurent Geslin / Male Feral pigeon (Columba livia) touching female with his beak. Paris, France

Andrew Parkinson / Pair of Great Crested Grebes (Podiceps cristatus) during their elaborate courtship dance. March. Derbyshire, UK, March (non-ex)

Andrew Parkinson / Pair of Mallard ducks (Anas platyrhynchos) on a lake in dawn, Derbyshire, UK. April (non-ex)

Floris van Breugel / Burrowing Owls (Athene cunicularia) breeding pair standing near the entrance to their burrow, at sunset, Salton Sea, California, USA.

Vincent Grafhorst / African Lion (Panthera leo) pair mating, Khutse Game Reserve, Botswana

Vincent Grafhorst / African Lion (Panthera leo) male and female courting, Khutse Game Reserve, Botswana

Nick Upton / Pair of Flesh Flies (Sarcophaga sp.) mating, Wiltshire pastureland, UK, May.

Roger Powell / Stone Curlew (Burhinus oedicnemus) pair walking through a flower meadow, Castro Verde, Portugal, April

Steve Knell / Harlequin ducks (Histrionicus histrionicus) male chasing female on riverbank, Iceland, May

Claudio Contreras / Pair of Northern elephant seals (Mirounga angustirostris) male holding female during copulation, Guadalupe Island Biosphere Reserve, off the coast of Baja California, Mexico, January

Dietmar Nill / European hare (Lepus europaeus) mating pair boxing in field, Slovakia

Dietmar Nill / European hare (Lepus europaeus) pair boxing in field, Slovakia

Russell Cooper / Mating pair of Small Blue Butterflies (Cupido minimus) on plant stem, Surrey, England, UK

LYNN M. STONE / Whooper Swan (Cygnus cygnus) breeding pair on water with cygnet; captive

Edwin Giesbers / Kittiwake (Rissa tridactyla) pair interacting, Farne Islands, Northumberland, UK, June

Staffan Widstrand / Arabian oryx (Oryx leucoryx) family, Dubai Desert Conservation Reserve, Dubai, UAE, Endangered species

Graham Eaton / Velvet swimming crab (Necora puber) pair mating, Trefor, Wales, UK, July.

Mary McDonald / Hyacinth Macaws (Anodorhynchus hyacinthinus) pair perched in Palm tree, the Pantanal, Brazil, South America.

Petra Wegner / Great Dane, black coated bitch, and Magyar Vizsla /Hungarian Pointer, tan coated male, double portrait in profile together.

Michael D. Kern / Zoo Atlanta / Lemur leaf frog (Hylomantis lemur) mating pair, captive, Critically endangered, from Central America

Michel Roggo / Marble trout (Salmo trutta marmorata) morph of the Brown Trout, male and female at spawning ground, Tolminka river, Slovenia, 2005

Michel Roggo / Sockeye / Red Salmon (Oncorhynchus nerka) pair spawning on gravel ground, Adams river, British Columbia, Canada, 1990

Michel Roggo / European Graylings (Thymallus thymallus) spawning, male in foreground, Lake of Thoune, Switzerland, 1992

Laurent Geslin / Common sparrows (Passer domesticus) two females and a male flying in urban park, Paris. France, November.

Laurent Geslin / Common sparrows (Passer domesticus) two males and a female flying, Paris. France, November.

Laurent Geslin / Mallard ducks (Anas platyrhynchos) male and female flying in Paris, France. March.

Nick Garbutt / Chin-strap Penguin (Pygoscelis antarcticus) displaying. Half-Moon Island, South Shetland Islands, Antarctica. February. (digitally stitched image)

Charlie Summers / King / Imperial Cormorants (Phalacrocorax albiventer) breeding pair display courtship behaviour in the form of a ritual dance at their nesting site on Saunders Island, Falkland Islands

Aflo / Black footed albatross (Phoebastria nigripes) pair displaying, Midway Islands, USA

Stephen Dalton / Common earwigs (Forficula auricularia) pair, male (left) and female (right), UK

Kristel Richard / A wild Misaki-uma breeding stallion (right) brings back one of his mares to his band while another breeding stallion (left) charges him away, in the Cape Toi Reserve, Miyazaki Prefecture, Kyushu Islan...

David Tipling / Two male Wigeon (Anas penelope) in courtship chase with female, Buckenham Marshes, Norfolk, England, winter

Niall Benvie / Young girl and boy playing in a wildflower meadow, Scotland, UK, July 2009

David Kjaer / Pair of Northern pintail ducks (Anas acuta) in flight, Gloucestershire, England

Gary K. Smith / Red Deer stag and hind (Cervus elaphus) silhouetted at sunset, Holkham Park, Norfolk, UK, December

Dietmar Nill / Little owl (Athene noctua) pair perched, courtship behaviour, Spain

Anup Shah / Grey-crowned crane pair (Balearica regulorum) Masai Mara National Reserve, Kenya. December

Anup Shah / Grey-crowned cranes (Balearica regulorum)displaying. Masai Mara National Reserve, Kenya. December

Solvin Zankl / Mating swarm of Long-tailed / Tisza mayflies (Palingenia longicauda) Tisza river, Hungary, Every female is approached by several mature males. Eventually the female mates with one of them on the water...