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

Tony Wu / Genital slit of a dead male Blue whale (Balaenoptera musculus) found floating south of Mirissa, Sri Lanka. Indian Ocean. The tip of the whale's penis appears to be protruding from the animal. The whal...

Tony Wu / Humpback whales (Megaptera novaeangliae) three males during social behaviour, one nuzzling the genital area of another. Vava'u, Tonga, Pacific Ocean.

Denis-Huot / Grant's zebra (Equus quagga boehmi) mating, Masai Mara Game Reserve, Kenya, October.

Enrique Lopez-Tapia / Traditional outfit of Melanesian man, Tanna Island, Tafea Province, Vanuatu, September 2008.

Anup Shah / African elephant (Loxodonta africana) male unsuccessfully mating with a female. Maasai Mara National Reserve, Kenya. Feb 2012.

Anup Shah / Olive baboon (Papio anubis) male watching with curiosity. Masai Mara National Reserve, Kenya. Taken with remote wide angle camera.

Ann & Steve Toon / Wild elephant (Loxodonta africana), vas deferens, removed during keyhole surgery in the bush. Private game reserve in Limpopo, South Africa, April 2011. Winner of the IUCN grant in the Melvita Natu...

Doc White / Humpback Whale (Megaptera novaeangliae) calf, underside view, genital slit visible, Tonga, South Pacific, September.

Roland Seitre / Brazilian Tapir (Tapirus terrestris) genital area with parasitic tics. Captive. Medellin Zoo, Antioquia, Colombia.

Florian Möllers / Female Chimpanzee (Pan troglodytes schweinfurthii) "Lola" (18 years) with large genital swelling feeding on juvenile Red-Tail Monkey (Cercopithecus ascanius) in a tree. Budongo Forest Reserve, Masindi...

Florian Möllers / Female Chimpanzee (Pan troglodytes schweinfurthii) "Lola" (18 years) with large genital swelling feeding on juvenile Red-Tail Monkey (Cercopithecus ascanius) in a tree. Budongo Forest Reserve, Masindi...