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

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...

Luciano Candisani / Green Anaconda (Eunectes murinus) female constricting male after copulation, after which she will consume him, Brazil

Cyril Ruoso / Bonobo (Pan paniscus) male and female copulating, Lola ya Bonobo Sanctuary, Democratic Republic of Congo

Jussi Murtosaari / Woodland brown butterflies (Lopinga achine) copulating, Kanta-Hame, southern Finland, June.

Matthias Breiter / Red-sided Garter Snake (Thamnophis sirtalis parietalis) group mating after hibernation, Narcisse, Manitoba, Canada

Hiroya Minakuchi / Nudibranch (Hypselodoris bullockii) pair mating, Borneo, Malaysia

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

Vincent Grafhorst / African Lion (Panthera leo) pair copulating, Moremi Game Reserve, Okavango Delta, Botswana

Vincent Grafhorst / African Lion (Panthera leo) pair copulating, Moremi Game Reserve, Okavango Delta, Botswana

Thomas Marent / Golden Poison Dart Frog (Phyllobates terribilis) pair mating, Cauca, Colombia

Mitsuaki Iwago / African Lion (Panthera leo) mating pair quarreling, Serengeti National Park, Tanzania

ZSSD / Panamanian Golden Frog (Atelopus zeteki) pair in amplexus, native to Panama

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

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

Mark Moffett / True Weevil (Eupholus sp) pair mating, Hala, Papua New Guinea

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

Fred Bavendam / Horseshoe Crab (Limulus polyphemus) group crawling ashore on the high tides of spring to lay their eggs in Delaware Bay's sandy beaches, New Jersey

Nick Upton / Kestrel (Falco tinnunculus) pair copulating on cliff ledge, Cornwall, UK, April.

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

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

Ch'ien Lee / Bornean Smaller Flying Frog (Rhacophorus borneensis) pair in amplexus, Danum Valley Conservation Area, Borneo, Sabah, Malaysia

Ralph Pace / Olive Ridley Sea Turtle (Lepidochelys olivacea) pair mating, Oaxaca, Mexico

Tui De Roy / Blue-footed booby (Sula nebouxii), pair copulating. South Coast, Santa Cruz Island, Galapagos.

Piotr Naskrecki / Light Webbed Ringlet (Physcaeneura pione) pair mating, Gorongosa National Park, Mozambique

Piotr Naskrecki / Mantid (Miomantis sp) female feeding on male after mating, Gorongosa National Park, Mozambique

Piotr Naskrecki / European Mantid (Mantis religiosa) female feeding on male after mating, Gorongosa National Park, Mozambique

Piotr Naskrecki / Mantid (Taumantis globiceps) pair mating, Gorongosa National Park, Mozambique

David Tipling / Pied avocet (Recurvirostra avosetta) pair copulating North Norfolk, England, UK. May

Paul Bertner / Millipede pair mating, Udzungwa Mountains National Park, Tanzania

Paul Bertner / Millipedes mating, Udzungwa Mountains National Park, Tanzania

Paul Bertner / Millipede pair mating, Udzungwa Mountains National Park, Tanzania

Paul Bertner / Cockroach pair mating, Andasibe-Mantadia National Park, Madagascar

Winfried Wisniewski / Lesser Kestrel (Falco naumanni) pair mating, Castile-La Mancha, Spain

Nick Upton / Kestrel (Falco tinnunculus) pair copulating on cliff ledge, Cornwall, UK, April.

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

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

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

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

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

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

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

Willi Rolfes/ BIA / White Stork (Ciconia ciconia) pair mating, Lower Saxony, Germany

Tui De Roy / King Penguin (Aptenodytes patagonicus) pair mating, Volunteer Beach, East Falkland Island, Falkland Islands

Tui De Roy / King Penguin (Aptenodytes patagonicus) pair mating, Volunteer Beach, East Falkland Island, Falkland Islands

Tui De Roy / Swallow-tailed Gull (Creagrus furcatus) pair mating, Gardner Islet, Floreana Island, Galapagos Islands, Ecuador

Tui De Roy / Swallow-tailed Gull (Creagrus furcatus) pair mating, Genovesa Island, Galapagos Islands, Ecuador

Tui De Roy / Green Sea Turtle (Chelonia mydas) pair mating in the surf, Espumilla Beach, Santiago Island, Galapagos Islands, Ecuador

Paul Bertner / Fruit Fly (Tephritidae) pair mating, with mite on back, Gunung Leuser National Park, Sumatra, Indonesia

Paul Bertner / Hoverfly (Microdon sp) pair mating, Udzungwa Mountains National Park, Tanzania

Paul Bertner / Hoverfly (Microdon sp) pair mating, Udzungwa Mountains National Park, Tanzania

Paul Bertner / Katydid (Typophyllum sp) pair mating, Amazon, Ecuador

Paul Bertner / Leaf Beetle (Chrysomelidae) pair mating, Udzungwa Mountains National Park, Tanzania

Paul Bertner / Glass Frog (Cochranella mache) pair mating, Ecuador

Paul Bertner / Fly (Pipunculidae) pair mating, Antananarivo, Madagascar

Nick Upton / Group of Yellow dung flies (Scathophaga stercoraria), some in copulating pairs, feeding on sheep dung, Wiltshire, England, UK, March. Slow motion clip.

Nick Upton / Group of Yellow dung flies (Scathophaga stercoraria), some in copulating pairs, feeding on sheep dung, Wiltshire, England, UK, March.

Nick Upton / Group of Yellow dung flies (Scathophaga stercoraria), some in copulating pairs, feeding on sheep dung, Wiltshire, England, UK, March.

Ingo Arndt / Niobe Fritillary (Argynnis niobe) pair mating, eastern Mongolia

Thomas Marent / Menapis Tigerwing (Mechanitis menapis) butterflies mating, Rio Claro Nature Reserve, Antioquia, Colombia

Thomas Marent / Leaf Frog (Cochranella spinosa) pair mating, San Cipriano, Colombia

Alfred Trunk/ BIA / Common Frog (Rana temporaria) pair in amplexus on snow, Austria

Nate Chappell/ BIA / Black Skimmer (Rynchops niger) pair mating, Texas

Nate Chappell/ BIA / Snow Goose (Chen caerulescens) pair mating, New Mexico

Marie Read / American avocet (Recurvirostra americana) 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,...

Marie Read / American Avocet (Recurvirostra americana), pair copulating, Bear River Migratory Bird Refuge, Utah, USA, May.

Hiroya Minakuchi / Orca (Orcinus orca) pair mating, Hokkaido, Japan

Pascal Pittorino / Common blue butterflies (Polyommatus icarus) pair copulating. Haute-loire, Auvergne, France, August

Michael Milicia/ BIA / Least Tern (Sterna antillarum) pair mating, North America

Ingo Arndt / Tisza Mayfly (Palingenia longicauda) swarming, Danube Delta, Romania

Ingo Arndt / Whiskered Tern (Chlidonias hybrida) pair mating on newly built nest, Danube Delta, Romania

Ingo Arndt / Whiskered Tern (Chlidonias hybrida) pair mating on newly built nest, Danube Delta, Romania

Ingo Arndt / Great Grey Slug (Limax maximus) pair mating while hanging from mucus string, Switzerland

Ingo Arndt / Great Grey Slug (Limax maximus) pair mating, Switzerland

Heike Odermatt / Southern Elephant Seal (Mirounga leonina) pair mating, Sea Lion Island, Falkland Islands

Heike Odermatt / Southern Elephant Seal (Mirounga leonina) pair mating, Sea Lion Island, Falkland Islands

Chien Lee / Long Horn Beetle (Pericycos teragramus) pair mating, Kubah National Park, Sarawak, Borneo, Malaysia

Ingo Arndt / African Lion (Panthera leo) male and female snarling during mating, Masai Mara, Kenya

Konrad Wothe / Moor Frog (Rana arvalis) pair in amplexus, Bavaria, Germany

Donald M. Jones / White-tailed Deer (Odocoileus virginianus) pair mating, central Montana

Hiroya Minakuchi / Southern Elephant Seal (Mirounga leonina) pair mating, South Georgia Island

Theo Allofs / African Lion (Panthera leo) pair mating, Masai Mara, Kenya

Pete Oxford / Toad (Atelopus sp) pair in amplexus, new undescribed species, native to Ecuador

Pete Oxford / Toad (Atelopus sp) pair in amplexus, new undescribed species, native to Ecuador

Thomas Marent / Gelada Baboon (Theropithecus gelada) pair mating, Simien Mountains National Park, Ethiopia

Thomas Marent / Gelada Baboon (Theropithecus gelada) pair mating, Simien Mountains National Park, Ethiopia

Thomas Marent / Gelada Baboon (Theropithecus gelada) pair mating, Simien Mountains National Park, Ethiopia

Roger Powell / European roller (Coracias garrulus) pair copulating on a eucalyptus branch. Monte da Aparica, Castro Verde, Alentejo, Portugal, May.

Roger Powell / European roller (Coracias garrulus) pair copulating on a eucalyptus branch. Monte da Aparica, Castro Verde, Alentejo, Portugal, May.

Roger Powell / Pied avocets (Recurvirostra avosetta) copulating in the water. Oosterendl, Texel Island, The Netherlands.

Sean Crane / Eastern Lubber Grasshopper (Romalea guttata) pair mating, Fakahatchee Strand Preserve State Park, Florida

Chien Lee / Ground Beetle (Calomera crespignyi) pair mating, Danum Valley Field Center, Sabah, Borneo, Malaysia

Chien Lee / Stick Insect (Phasmatidae) pair mating, Gunung Penrissen, Borneo, Malaysia

Cyril Ruoso / Bonobo (Pan paniscus) male and female copulating, Lola ya Bonobo Sanctuary, Democratic Republic of Congo

Cyril Ruoso / Bonobo (Pan paniscus) male and female copulating, Lola ya Bonobo Sanctuary, Democratic Republic of Congo

Cyril Ruoso / Bonobo (Pan paniscus) male and female copulating in water, Lola ya Bonobo Sanctuary, Democratic Republic of Congo