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

Espen Bergersen / Aerial shot of Killer whales (Orcinus orca) near the surface, showing mating behaviour including a male Killer whale displaying penis, Troms, Norway, August.

Ralph Pace / Swell Shark (Cephaloscyllium ventriosum) egg case and embryo, Monterey, California

Gary Bell/ Oceanwide / Intermediate Cardinalfish (Cheilodipterus intermedius) male incubating eggs in mouth, Great Barrier Reef, Australia

Gary Bell/ Oceanwide / Intermediate Cardinalfish (Cheilodipterus intermedius) male incubating eggs in mouth, Great Barrier Reef, Australia

Gary Bell/ Oceanwide / Intermediate Cardinalfish (Cheilodipterus intermedius) male incubating eggs in mouth, Great Barrier Reef, Australia

Franco Banfi / Sperm whale (Physeter macrocephalus) young male trying to copulate with a female. The calf of the female was in the way so the male is trying to chase it away. Dominica.

Dave Bevan / Female Giant wood wasp (Uroceras gigas) inserting ovipositor into tree stump to lay eggs, Carmarthenshire, Wales, UK, September.

Tui De Roy / Blue-footed Booby (Sula nebouxii) incubating eggs, Santa Cruz Island, Galapagos Islands, Ecuador

Tony Wu / Humpback whale (Megaptera novaeangliae) male with his penis extended. Vava'u, Tonga. South Pacific.

Thomas Marent / Douc Langur (Pygathrix nemaeus) male, native to southeast Asia

Alex Mustard / Black hamlet (Hypoplectrus nigricans) and Yellowbelly hamlet (Hypoplectrus aberrans) spawning at dusk. As this genus is quite recently evolved hybridization is still possible. Hamlets are one of the...

Pete Oxford / American Crocodile (Crocodylus acutus) nest excavated by nesting female Green Iguana (Iguana iguana), Banco Chinchorro, Yucatan Peninsula, Mexico

Yukihiro Fukuda / Japanese macaque (Macaca fuscata fuscata) rare white furred baby jumping, Jigokudani Valley, Nagano Prefecture, Japan. June.

Yukihiro Fukuda / Japanese macaque (Macaca fuscata fuscata) mother with rare white furred male baby, Jigokudani Valley, Nagano Prefecture, Japan. June.

Chien Lee / Red Stink Bug (Pycanum rubeus) hatchlings cluster to amplify the effect of their aposematic warning coloration, Malaysia

Michael Quinton / Northern Flicker (Colaptes auratus) eggs in nest cavity, Alaska

Connor Stefanison / Red-necked Grebe (Podiceps grisegena) at nest in swamp, British Columbia, Canada

D. Parer & E. Parer-Cook / Giant Clam (Tridacna gigas) spawning, Great Barrier Reef, Queensland, Australia

Piotr Naskrecki / Cross Frog (Oreophryne sp) male protecting his clutch of eggs, Papua New Guinea

Piotr Naskrecki / Ground Frog (Platymantis boulengeri) female protecting her clutch of eggs, Papua New Guinea

Piotr Naskrecki / Cross Frog (Oreophryne sp) male from a newly discovered species protecting his clutch of eggs, Papua New Guinea

Piotr Naskrecki / Cross Frog (Oreophryne sp), newly discovered species, eggs, Papua New Guinea

Pete Oxford / Black-browed Albatross (Thalassarche melanophrys) nesting colony, Steeple Jason Island, Falkland Islands

Ingo Arndt / Brown Trout (Salmo trutta) eggs, fish already visible through egg-shell, Europe

Scott Leslie / Frog egg mass, Nova Scotia, Canada

Michael Durham / Coho Salmon (Oncorhynchus kisutch) eggs at ten weeks after spawning, Washington

Ingo Arndt / Blue Morpho (Morpho peleides) caterpillar hatching out of egg, Costa Rica

Ingo Arndt / Blue Morpho (Morpho peleides) caterpillar hatching out of egg, Costa Rica

Ingo Arndt / Blue Morpho (Morpho peleides) butterfly egg, Costa Rica

Birgitte Wilms / Nudibranch laying eggs, Indonesia

Piotr Naskrecki / Eggs of an unidentified insect, Guinea, West Africa

Michael Quinton / Great Gray Owl (Strix nebulosa) parent protecting eggs in nest, North America

Mitsuaki Iwago / Green Sea Turtle (Chelonia mydas) female laying eggs in nest on beach, endangered, Hawaii

Ross Hoddinott / Azure damselflies mating {Coenagrion puella} Cornwall, UK. Damselflies have brushes on their penises that they use to scoop rival sperm from the female's reproductive tract, thereby ensuring pate...

Michael & Patricia Fogden / Common Egg-eating Snake (Dasypeltis scabra) swallowing egg from another animal's nest, savannah, South Africa

Fred Bavendam / Pacific Giant Octopus (Enteroctopus dofleini) female guarding her eggs, Quadra Island, British Columbia, Canada

Michael & Patricia Fogden / Common Egg-eating Snake (Dasypeltis scabra) swallowing egg, Africa

Tom Vezo / Piping Plover (Charadrius melodus) sitting on eggs in nest on ground, Long Island, New York

Gerry Ellis / Magnificent Hummingbird (Eugenes fulgens) nest with three eggs, Costa Rica

Michael & Patricia Fogden / Bushmaster (Lachesis muta) baby hatching from egg, lowland rainforest on Atlantic slope of Costa Rica

Chris Newbert / Yellow-striped Cardinalfish (Apogon cyanosoma) male with eggs in mouth, 40 feet deep, Solomon Islands

Chris Newbert / Pink Anemonefish (Amphiprion perideraion) in Magnificent Sea Anemone (Heteractis magnifica) the fish will bite the Anemone causing it to ball-up so the fish can lay or tend to their eggs at the foot o...

Flip de Nooyer / Common Eider (Somateria mollissima) adult female at down nest with eggs, Europe

Heidi & Hans-Juergen Koch / Glass Frog (Cochranella antisthenesi) transparent skin shows body filled with eggs, very rare and fragile frog, native to Central and South America

Sumio Harada / American Robin (Turdus migratorius) newly-hatched day old chicks begging in nest with unhatched blue egg, Glacier National Park, Montana

Gerry Ellis / Greater Flamingo (Phoenicopterus ruber) nesting colony with mud nests, Inagua National Park, Bahamas

Konrad Wothe / Kentish Plover (Charadrius alexandrinus) male at nest, Europe

Jim Brandenburg / Western Grebe (Aechmophorus occidentalis) nest with egg floating in prairie pothole, Aberdeen, South Dakota

Fred Bavendam / Stony Coral (Acropora sp) colony releasing egg-sperm bundles during the mass coral spawning each March at Ningaloo Reef, Western Australia

Fred Bavendam / Staghorn Coral (Acropora cervicornis) colony releasing egg-sperm bundles during the mass coral spawning each March at Ningaloo Reef, Western Australia

Fred Bavendam / Ring-tailed Cardinalfish (Apogon aureus) male protectively carrying a fertilized egg mass in his mouth while they incubate, Bali, Indonesia

Michael Quinton / Red-necked Grebe (Podiceps grisegena) parent on nest with eggs in boreal pond, Alaska

Tui De Roy / Blue-footed Booby (Sula nebouxii) male incubating eggs with webbed feet, Seymour Island, Galapagos Islands, Ecuador

Tui De Roy / Black-footed Albatross (Phoebastria nigripes) incubating single egg, Midway Atoll, Hawaii

Tui De Roy / Adelie Penguin (Pygoscelis adeliae) newly hatched chick, second egg pipping, Peterson Island, Wilkes Land, East Antarctica

Mitsuaki Iwago / King Penguin (Aptenodytes patagonicus) adult attends to its single egg balanced on its feet, South Georgia Island

Fred Bavendam / Pacific Giant Octopus (Enteroctopus dofleini) eggs and newborn, Victoria, British Columbia, Canada

Fred Bavendam / Pacific Giant Octopus (Enteroctopus dofleini) eggs and newborn, Victoria, British Columbia, Canada

Fred Bavendam / Paper Nautilus (Argonauta nodosa) is actually a pelagic Octopus, females make the parchment-like shell to carry incubating eggs, South Australia

Michael Quinton / Canada Goose (Branta canadensis) hatchlings in nest with unhatched eggs, spring, Idaho

Norbert Wu / California Two-spot Octopus (Octopus bimaculoides) juveniles hatch from egg cases, southern California

Michael Quinton / Common Loon (Gavia immer) chick with hatching egg in nest in the summer, Wyoming

Norbert Wu / Devil Angler (Linophryne sp) deep sea species larvae with large yolky egg which is a deep sea reproductive strategy, Celebes Sea

Fred Bavendam / Giant Damselfish (Microspathodon dorsalis) male guarding eggs laid on a rock ledge Galapagos Islands, Ecuador

Fred Bavendam / Australian Giant Cuttlefish (Sepia apama) hatchling swimming past the egg of an unhatched sibling after an incubation of about four months, southern Australia

Fred Bavendam / Pacific Giant Octopus (Enteroctopus dofleini) eggs, Victoria, British Columbia, Canada

Fred Bavendam / Leafy Sea Dragon (Phycodurus eques) male carrying eggs that a female has recently deposited onto his tail, Kangaroo Island, South Australia

Mark Jones / North Island Brown Kiwi (Apteryx australis mantelli) parent with egg,/nOtorohanga Breeding Facility, New Zealand

Tui De Roy / Adelie Penguin (Pygoscelis adeliae) chick begging food from parent, Foyn Island, Possession Islands, Ross Sea, Antarctica

Mitsuaki Iwago / Loggerhead Sea Turtle (Caretta caretta) hatchling emerging from underground nest on sandy beach, Australia

Fred Bavendam / Stony Coral (Acropora sp) colony releasing egg-sperm bundles during the annual mass coral spawning on the Great Barrier Reef, Queensland, Australia

Fred Bavendam / Spotfin Jawfish (Opistognathus sp) male protectively incubating a clutch of eggs in his mouth, Manado, North Sulawesi, Indonesia

Fred Bavendam / Blackfinned Clownfish (Amphiprion percula) guarding eggs laid beside their Magnificent Sea Anemone (Heteractis magnifica) host, Kimbe Bay, Papua New Guinea

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

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

Fred Bavendam / Horseshoe Crab (Limulus polyphemus) eggs almost ready to hatch after two weeks incubation in the warm sands of Cape Anne, Massachusetts

Charlie Summers / Lion (Panthera leo) ready to mount female, Ngorongoro Crater, Tanzania.

Andy Rouse / Bengal tiger (Panthera tigris) male rolling on ground after mating. Ranthambhore National Park, India.

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

Doug Gimesy / Grey-headed Flying-fox (Pteropus poliocephalus) hangs from one foot from a branch. Yarra Bend Park, Kew, Victoria, Australia. December, 2017.

Heather Angel / Chalcid wasp (Gasteruption jaculator) nectaring on Yarrow (Achillea millefolium) cultivar, picking up pollen on legs and head. Long ovipositor used to lays eggs inside solitary bee nests. In garden, S...

Andy Rouse / Indian Flying Fox , (Pteropus giganteus), roosting, India

Paul Bertner / Lacewing larvae hatching, Tambopata Research Center, Peru

Gary Bell/ Oceanwide / Saddleback Anemonefish (Amphiprion polymnus) guarding eggs by sea anemone, Anilao, Philippines

Gary Bell/ Oceanwide / Pink Anemonefish (Amphiprion perideraion) male in sea anemone, Great Barrier Reef, Australia

Gary Bell/ Oceanwide / Intermediate Cardinalfish (Cheilodipterus intermedius) male incubating eggs in mouth, Great Barrier Reef, Australia

Anup Shah / Olive baboon (Papio anubis) male, taken with remote camera. Masai Mara National Reserve, Kenya.

Anup Shah / Vervet monkey (Cercopithecus aethiops) male approaching with curiosity - remote camera. Masai Mara National Reserve, Kenya..

Agustin Esmoris / Turkey Vulture (Cathartes aura) eggs in nest, Chubut, Argentina

Agustin Esmoris / Black-browed Albatross (Thalassarche melanophrys) incubating egg on nest, Falkland Islands

Agustin Esmoris / Gentoo Penguin (Pygoscelis papua) incubating egg on nest in colony, Falkland Islands

Agustin Esmoris / Gentoo Penguin (Pygoscelis papua) tending to egg on nest in colony, Falkland Islands

Agustin Esmoris / Gentoo Penguin (Pygoscelis papua) incubating egg on nest in colony, Falkland Islands

Agustin Esmoris / Gentoo Penguin (Pygoscelis papua) adjusting egg in nest, Falkland Islands