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

Marie Lochman / Carpet of annual everlasting daisies, Everlastings (Rhodanthe chlorocephala subsp. splendida) in flower, Midwest, Karara Rangelands, Western Australia. September 2018

Guy Edwardes / Close up of a sunflower (Helianthus annuus) head, Provence, France.

Guy Edwardes / Close up of a sunflower (Helianthus annuus) head, Provence, France.

Ingo Arndt / Grizzly Bear (Ursus arctos horribilis) waiting for salmon under moonlit sky, Lake Clark National Park, Alaska, USA, August

Ingo Arndt / Grizzly Bear (Ursus arctos horribilis) waiting for salmon at full moon, Lake Clark National Park, Alaska, USA, August

Ingo Arndt / Mayflies (Palingenia longicauda) swarming, Tisza river, Hungary, June

Ingo Arndt / Christmas Island Red Crab (Gecarcoidea natalis) blurred view of vast number of individuals moving along their annual migration route, Christmas Island, Indian Ocean, Australian Territory

Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) crossing closed road, during annual migration, Christmas Island, Indian Ocean, Australian Territory, November 2009.

Ingo Arndt / Christmas Island Red Crabs (Gecarcoidea natalis) crossing road in huge numbers during annual migration, Christmas Island, Indian Ocean, Australian Territory

Yashpal Rathore / Demoiselle crane (Anthropoides virgo) low angle view of birds flying and landing near the chugga ghar (bird feeding enclosure ) in Khichan Village, durin their annual migration. Western Rajasthan, Ind...

Wim van den Heever / Bottlenose Dolphin (Tursiops truncates) mother and calf porpoising during annual Sardine run, Port St Johns, South Africa, June.