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.

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.

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

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.

Fiona Rogers / Wild mature male mandrill (Mandrillus sphinx) in gallery forest during dry season. Lope National Park, Gabon. June 2008.

Wild Wonders of Europe / E Haarberg / Chamois (Rupicapra rupicapra) male with erect penis in rutting season, Gran Paradiso National Park, Italy, November 2008

Karl Ammann / Male Bonobo {Pan paniscus} sitting, looking thoughtful. Lola Ya Bonobo Sanctuary, Kinshasa, DR of Congo, 2007

Doug Perrine / Humpback whale {Megaptera novaeangliae} with penis extended, Pacific (taken under NMFS research permit 882 issued by Hawai Whale Research Foundation)

Anup Shah / Hamadryas baboons display red bottoms {Papio hamadryas} C

Brandon Cole / Sexual play between Bottlenose {Tursiops truncatus} and Atlantic spotted dolphins {Stenella frontalis} Bahamas, Caribbean NOT FOR SALE IN USA. Dolphins are notorious for trying to mate with anything -...

Francois Savigny / Tiger male carrying Chital deer kill, Bandhavgarh NP, Madhya Pradesh, India

Hermann Brehm / African elephant male in musth charging {Loxodonta africana} Botswana

Anup Shah / Male Chimpanzee sitting on tree buttress, Gombe NP Tanzania. Apollo

Etienne Littlefair / Irwin's turtle (Elseya irwini), adult male resting. Note the sediment disturbance to the rear of the turtle is caused by expulsion of water via cloacal respiration. North Johnstone River, downstre...

Nick Upton / Ichneumon wasp (Ichneumonidae / Pimplinae) female with a long ovipositor grooming its abdomen while sunning on a Dogwood leaf on a chalk grassland slope, Bath and Northeast Somerset, UK, May.

Aaron Gekoski / A dog penis bracelet, held by human hands. A good luck charm in Cambodia. October 2019.

Ingo Arndt / Honey bee (Apis mellifera), dead drone at nest entrance. Visible genitals/penis, Germany.

James Dunbar / Hoverfly (Epistrophe grossulariae) attempting to lay eggs amongst aphids. Ovipositor visible, April, UK

James Dunbar / Hoverfly (Epistrophe grossulariae) taking off from flower and landing again, April, UK

Will Watson / Male Vervet monkey (Chlorocebus aethiops) eating a mango fruit, showing blue scrotum, Samburu Lodge, Kenya. January.

Andy Sands / Ichnumen wasp (Lissonata Sp.) female resting on a Bluebell flower, Hertfordshire, England, UK, April - Focus Stacked

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

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

Shane Gross / Nurse sharks (Ginglymostoma cirratum) ready to mate. Showing male claspers, which are used to channel semen into the female during mating, Eleuthera, Bahamas.

Shane Gross / Nurse sharks (Ginglymostoma cirratum) ready to mate. Showing male claspers, which are used to channel semen into the female during mating, Eleuthera, Bahamas.

David Perpinan / Necrosis / tissue dying in hemipenis of captive garter snake (Thamnophis sirtalis) small repro only

David Perpinan / Phallus/penile prolapse in a captive Yellow bellied slider (Trachemys scripta). Small repro only

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..

Franco Banfi / Zebu bull, Bonito, Mato Grosso do Sul, Brazil

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

Staffan Widstrand / Wild Wonders of China / Portrait of a male Golden snub-nosed monkey (Rhinopithecus roxellana) Foping Nature Reserve, Shaanxi, China. Endangered species

Claudio Contreras / Olive Ridley Sea Turtle (Lepidochelys olivacea) nesting, egg in nest, Arribada (mass nesting event), Playa Morro Ayuta, Oaxaca state, southern Mexico, IUCN Vulnerable, August

Daniel Heuclin / Potto (Perodicticus potto) male in tree, Togo. Captive.

Kim Taylor / Rose sawfly (Arge ochropus) female cutting a groove in a rose stem in which to lay her eggs. Surrey, England, UK, June.

Kim Taylor / Parasitic wasps (Braconidae) approaching caterpillar of Lesser willow sawfly (Nematus pavidus) to lay eggs on, Surrey, England, UK. June.

Kim Taylor / Parasitic wasps (Braconidae) approaching caterpillar of Lesser willow sawfly (Nematus pavidus) to lay eggs on, Surrey, England, UK. June.

Kim Taylor / Parasitic wasp (Braconidae) with ovipositor extended approaching caterpillar of Lesser Willow Sawfly (Nematus pavidus). Surrey, England, June.

Kim Taylor / Parasitic wasp (Braconidae) with ovipositor extended approaching caterpillar of Lesser Willow Sawfly (Nematus pavidus). Surrey, England, June.

MYN / Lily Kumpe / Balloon-winged katydid (Tympanophora diminuta) female, William Bay National Park, Western Australia. Meetyourneighbours.net project.

MYN / Lily Kumpe / Giant ichneumon wasp (Megarhyssa) female with very long ovipositor, Dugana Khad, Tuv Province, Mongolia. Meetyourneighbours.net project.

Tony Wu / Humpback whale (Megaptera novaeangliae) male blowing bubbles, likely a display of dominance during heat run. The male had a small portion of his penis protruding. Vava'u, Tonga. Pacific Ocean.

Dave Bevan / Female Giant wood wasp (Uroceras gigas) withdrawing ovipositor from tree stump after laying eggs, Carmarthenshire, Wales, UK, September.

Klein & Hubert / Aubrac bull - close up of testicles, France