Alex Mustard / Yellowtail tang (Zebrasoma xanthurum) male and female turn belly to belly during spawning to ensure fertilization. Temple, Ras Umm Sid, Sharm El Sheikh, Sinai, Egypt. Red Sea. This action is very fast...

Martin Willis / Rainbow Lorikeet (Trichoglossus haematodus) pair preening during courtship, Magnetic Island, Queensland, Australia

Danny Green / Reindeer (Rangifer tarandus) hunkering down in snow during blizzard. Svalbard, Norway, April.

Theo Bosboom / Powerful waves rolling in at the Atlantic coast of Iceland near Dyrholey during a powerful winter storm. February 2016

Tony Wu / View down the throat of a male Zoarchias major eelpout (Zoarchias major) that has opened its mouth during a confrontation with another male. Yamaguchi Prefecture, Japan. Pacific Ocean.

Jack Dykinga / Saguaro cacti (Carnegia gigantea) at sunset, during a summer rain storm. Saguaro National Park, Sonoran Desert, Arizona, USA, August. Digital composite.

John Shaw / Black-browed albatross pair (Thalassarche melanophris) mutual grooming during copulation. New Island, Falkland Islands, November.

Shane Gross / Elkhorn corals (Acropora palmata) at night silhouetted by a scientist's light during the annual coral spawn. Abaco, Bahamas.

John Chan / Two male Southern Pacific rattlesnakes (Crotalus oreganus helleri) fighting during mating season. This behaviour is known as a "combat dance", and is used to determine dominance and the right to mate...

Sandesh Kadur / Slow motion clip of Amur falcons (Falco amurensis) congregating at roost site during their migration from Siberia to Africa, near Doyang reservoir, Nagaland, India, October.

Sandesh Kadur / Amur falcons (Falco amurensis) congregating during their migration from Siberia to Africa, near Doyang reservoir, Nagaland, India, October.

Sandesh Kadur / Amur falcons (Falco amurensis) congregating during their migration from Siberia to Africa, near Doyang reservoir, Nagaland, India, October.