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

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

Wild Wonders of Europe / Varesvuo / Red-footed Falcon (Falco vespertinus) pair perched, male on left, Hortobagy NP, Hungary, May 2008

Wild Wonders of Europe / Varesvuo / Red-footed falcon (Falco vespertinus) mating pair, Hortobagy NP, Hungary, May 2008

Wild Wonders of Europe / Varesvuo / Red-footed falcon (Falco vespertinus) mating pair, Hortobagy NP, Hungary, May 2008

Wild Wonders of Europe / Varesvuo / Red-footed Falcon (Falco vespertinus) male brings vole prey to female in nestbox, Hortobagy NP, Hungary, May 2008

Wild Wonders of Europe / Varesvuo / Red-footed falcon (Falco vespertinus) mating pair, Hortobagy NP, Hungary, May 2008

Wild Wonders of Europe / Varesvuo / Red-footed Falcon (Falco vespertinus) mating pair, Hortobagy NP, Hungary, May 2008

Wild Wonders of Europe / Varesvuo / Red-footed Falcon (Falco vespertinus) mating pair, Hortobagy NP, Hungary

Thomas Marent / Banana Spider (Nephila clavipes) female and smaller male, Bocas del Toro, Panama

Jasper Doest / Caribou (Rangifer tarandus) herd in snowy landscape, Abisko, Sweden

Piotr Naskrecki / Bearded Weevil (Rhinostomus barbirostris) species displays interesting sexual polymorphism, Costa Rica

Anup Shah / Fur Seal pair mating (Arctocephalus pusillus pusillus) Cape Cross Seal Reserve, Namibia

Anup Shah / Fur Seal pair mating (Arctocephalus pusillus pusillus) Cape Cross Seal Reserve, Namibia

Anup Shah / Fur Seal pair mating (Arctocephalus pusillus pusillus) Cape Cross Seal Reserve, Namibia

Gabriel Rojo / South American / Patagonian sealion pair {Otaria flavescens} on beach, Valdez peninsula, Argentina

Gabriel Rojo / South American / Patagonian sealion pair {Otaria flavescens} Valdez peninsula, Argentina

Gabriel Rojo / South American / Patagonian sealion pair mating {Otaria flavescens} Valdez peninsula, Argentina. Note large difference in size between male and female

Mitsuaki Iwago / African Lion (Panthera leo) couple fighting during mating, Serengeti National Park, Tanzania

Konrad Wothe / Mandarin Duck (Aix galericulata) male and female standing in water, China

Norbert Wu / Old-world Chameleons, male and female preparing to mate, Africa

Tui De Roy / Great Frigatebird (Fregata minor) courting males vying for female's attention, Genovesa Tower Island, Galapagos Islands, Ecuador

Mitsuaki Iwago / Australian Sea Lion (Neophoca cinerea) male approaching a female to mate, Australia

Tui De Roy / Great Frigatebird (Fregata minor) recently formed pair, female inspecting male in courtship display with extended gular pouch, Genovesa Tower Island, Galapagos Islands, Ecuador

David Shale / Deep sea Anglerfish male. Male is ten times smaller than female and has well developed olfactory system to help locate females in the darkness, Atlantic ocean

Doug Allan / Southern elephant seal pair courtship {Mirounga leonina} Antarctica

Doug Allan / Southern elephant seal pair courtship {Mirounga leonina} Antarctica. NB Large difference in size of male and female.

Nick Upton / Sexually dimorphic St. Mark's fly / March fly (Bibio marci) pair mating; males have much larger eyes and clear wings, Wiltshire garden, UK, May.

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

XI ZHINONG / Tibetan antelope (Pantholops hodgsoni) male with female, grazing, Kekexili, Qinghai, Tibetan Plateau, China, December

XI ZHINONG / Tibetan antelope (Pantholops hodgsonii) male with females following, Kekexili, Qinghai, Tibetan Plateau, China, November

XI ZHINONG / Tibetan antelope (Pantholops hodgsoni) male chasing female, Kekexli, Qinghai, January.

Marie Read / Red-bellied Woodpecker (Melanerpes carolinus) pair, male calling, female in background, both clinging to treetrunk where their nest is located (not visible), Lakeland, Florida, USA, March.

Hiroya Minakuchi / Steller's Sea Lion (Eumetopias jubatus) female posturing at sub-adult male, Alaska

Chris Mattison / Mossy stick insect (Spinohirasea bengalensis), mating pair, captive, occurs South East Asia

Tim Fitzharris / Mandarin Duck (Aix galericulata) male and female, Jurong Bird Park, Singapore

Tim Fitzharris / Mandarin Duck (Aix galericulata) males competing over female, Jurong Bird Park, Singapore

Jim Brandenburg / Moose (Alces alces) bull and female in snow, North America

Thomas Marent / Condoto Stubfoot Toad (Atelopus spurrelli) pair in amplexus, Utria National Park, Colombia

MYN / Paul Marcellini / Painted bunting (Passerina ciris) pair perched, male on left, female on right, Homestead, Florida, USA, March . meetyourneighbours.net project

Martin Willis / Zebra Finch (Taeniopygia guttata) male and female, Townsville, Queensland, Australia

Martin Willis / Painted Firetail (Emblema pictum) male and female preening on branch, Winton, Western Queensland, Australia

Konrad Wothe / Wilson's Bird-of-paradise (Cicinnurus respublica) male displaying to female, Batanta Island, Indonesia

Nick Upton / 2020VISION / Common teal (Anas crecca) pair on partially frozen flooded marshland on a cold winter day, Greylake RSPB reserve, Somerset Levels, UK, January.

Piotr Naskrecki / Giant Wood Spider (Nephila maculata) male and much larger female mating, New Britain, Papua New Guinea

Donald M. Jones / White-tailed Deer (Odocoileus virginianus) male and female, western Montana

Donald M. Jones / Mountain Bluebird (Sialia currucoides) male bringing food to female in nest cavity, Troy, Montana

Donald M. Jones / Mountain Bluebird (Sialia currucoides) male and female at nest cavity, Troy, Montana

Donald M. Jones / Mountain Bluebird (Sialia currucoides) male bringing food to female in nest cavity, Troy, Montana

Colin Monteath / Domestic Sheep (Ovis aries) pair grazing beside Upland Goose (Chloephaga picta) group, Bluff Cove, Falkland Islands

Steve Gettle / Magnificent Frigatebird (Fregata magnificens) pair, Galapagos Islands, Ecuador

Martin Willis / Gouldian Finch (Chloebia gouldiae) male and female, Georgetown, Queensland, Australia

Steve Gettle / Ring-necked Duck (Aythya collaris) pair, Crow Island State Game Area, Michigan

Alex Hyde / Wasp spiders (Argiope bruennichi) female (left) and male (right) showing sexual dimorphism, digital composite, photographed on a white background. Midi-Pyrenees, France. August.

John Cancalosi / Masked Treefrogs (Smilisca phaeota) mating, in amplexus. Costa Rican tropical rainforest.

John Cancalosi / Masked Treefrogs (Smilisca phaeota) mating, in amplexus. Costa Rican tropical rainforest.

John Cancalosi / Masked Treefrogs (Smilisca phaeota) mating, in amplexus. Costa Rican tropical rainforest.

Steve Gettle / Wood Duck (Aix sponsa) pair with female on nest, Island Lake Recreation Area, Michigan

Steve Gettle / Wood Duck (Aix sponsa) pair, North Chagrin Reservation, Ohio

Steve Gettle / Wood Duck (Aix sponsa) pair swimming, Lapeer State Game Area, Michigan

Steve Gettle / Blue-winged Teal (Anas discors) male and female, J. Clark Salyer National Wildlife Refuge, North Dakota

Piotr Naskrecki / Lubber Grasshopper (Taeniopoda reticulata) pair mating, Barbilla National Park, Costa Rica

Piotr Naskrecki / Winter Moth (Operophtera brumata) pair mating, Woburn, Massachusetts

Theo Allofs / African Lion (Panthera leo) pair mating, Moremi Game Reserve, Okavango Delta, Botswana

Ernie Janes / Pheasant (Phasianus colchicus) male and females feeding on farmland, Norfolk, UK

Piotr Naskrecki / Giant Wood Spider (Nephila maculata) pair mating, Papua New Guinea

Piotr Naskrecki / Giant Wood Spider (Nephila maculata) male spinning web on female to make sure he does not fall off, Papua New Guinea

Piotr Naskrecki / Giant Wood Spider (Nephila maculata) pair mating, male is much smaller than female, Papua New Guinea

Piotr Naskrecki / Sagebrush Grig (Cyphoderris strepitans) female and male, Wyoming

Piotr Naskrecki / Sagebrush Grig (Cyphoderris strepitans) female and male, Wyoming

Bryan and Cherry Alexander / Injured bull Elephant seal (Mirounga genus) resting on top of one of his females. Gold Harbour, South Georgia.

Luiz Claudio Marigo / Male (the small spider) and female Golden Orb-web Spider (Nephila clavipes) on their web. Tayrona National Natural Park, municipality of Santa Marta, Magdalena Department, Colombia.

Luiz Claudio Marigo / Female Golden Orb-web Spider (Nephila clavipes) consuming a butterfly on her web. The much smaller male of the species is just by the abdomen of the female. Tayrona National Natural Park, municipality...

Konrad Wothe / Himalayan Tahr (Hemitragus jemlahicus) female and male, India

Richard Du Toit / Klipspringer (Oreotragus oreotragus) pair, Marakele National Park, Limpopo, South Africa

Michael Quinton / Barrow's Goldeneye (Bucephala islandica) pair mating, Alaska

Michael Quinton / Barrow's Goldeneye (Bucephala islandica) female courting male, Alaska

Markus Varesvuo / Steller's Eider (Polysticta stelleri) males and females on water. Norway, March. Magic Moments book plate, page 130-131.

Rod Williams / Splendid Fairy-wren (Malurus splendens) male and female pair perched, Captive occurs South western Australia.

Brent Stephenson / Large adult male Steller's Sea Lion (Eumetopias jubatus) resting on rocks surrounded by females of his harem. Inian Islands, Alaska, United States, July.

Hiroya Minakuchi / Southern Elephant Seal (Mirounga leonina) sub-adult male and female, South Shetland Islands, Antarctica

Donald M. Jones / White-tailed Deer (Odocoileus virginianus) buck and doe, western Montana

Donald M. Jones / Pine Grosbeak (Pinicola enucleator) male and female, western Montana

Daniel Heuclin / Barbour's Least Gecko (Sphaerodactylus torrei) male on log. Cuba, January.

Daniel Heuclin / Barbour's Least Gecko (Sphaerodactylus torrei) female resting on log. Cuba, January.

Florian Möllers / Slender orb web spider (Tetragnatha extensa) male (on left) and female on web, nature reserve NSG Gosener Wiesen, Berlin, Germany. July

Jouan & Rius / Stick insect (Epidares nolimetangere) mating pair, smaller male and larger female, Bako NP, Borneo, Sarawak, Malaysia

Frederique Olivier / Southern elephant seal (Mirounga leonina) mating pair with pup beside female, Macquarie Island, Southern Atlantic, Australian Antarctica, November

Inaki Relanzon / White collared / Grey-headed lemur (Eulemur cinereiceps) male (in front) and female (behind), captive, Manombo forest, Madagascar, critically endangered

Tui De Roy / Lichtenstein's Sandgrouse (Pterocles lichtensteinii) male and female, Borana Ranch, Kenya

Tui De Roy / Kirk's Dik-dik (Madoqua kirkii) female and male, Loisaba Wilderness, Kenya

Tui De Roy / Kirk's Dik-dik (Madoqua kirkii) female and male, Mpala Research Centre, Kenya

Tui De Roy / Greater Painted-snipe (Rostratula benghalensis) female and male, Loisaba Wilderness, Kenya

Andy Sands / Garden Ant (Lasius niger) female being mated by smaller black male. Hertfordshire, UK, August.