Tony Wu / Sperm whale (Physeter macrocephalus), ten swimming together in gathering of more than 50 individuals. Whales with flatulence and defecating. Sri Lanka.

Stefan Christmann / Emperor penguin (Aptenodytes forsteri) colony huddled together under the Southern Lights, Aurora australis, Atka Bay, Antarctica. September.

Jack Dykinga / Bighorm sheep (Ovis canadensis) males grouped together before the rutting season. Valley of Fire State Park, Nevada, USA, February.

Jordi Chias / Gentoo penguins (Pygoscelis papua) swimming together and porpoising in search of krill, Antarctic Peninsula, Antarctica.

Jordi Chias / Gentoo penguins (Pygoscelis papua) porpoising, swimming together in search of krill, Antarctic Peninsula, Antarctica.

Alex Mustard / School of White collar butterflyfish (Chaetodon collare) pack together above a coral reef. North Male Atoll, Maldives. Indian Ocean

SCOTLAND: The Big Picture / Orca whales (Orcinus orca) pod surfacing together, Shetland, Scotland, UK. April.

Marie Read / Western Grebe (Aechmorphus occidentalis), pair during 'rushing' courtship display in which they run across water's surface in synchrony, near Escondido, California, USA, January.

Marie Read / Black-necked stilts (Himantopus mexicanus) pair performing post-copulatory display (as copulation ends, the male slides off the female leaving his wings draped over her and crossing his bill with hers...

David Pattyn / Humpback whale (Megaptera novaeangliae) two breaching at the same time together, Puerto Lopez , Santa Elena Peninsula, Manabi Province, Ecuador, July, Puerto Lopez , Santa Elena Peninsula, Manabi Prov...

Lorraine Bennery / Red-bellied lemur (Eulemur rubriventer) huddling together in tree branches. Anjozorobe Special Reserve, Madagascar. Vulnerable species, endemic.

Stefan Christmann / Emperor penguin (Aptenodytes forsteri) breeding colony, mainly males brooding eggs, huddled together on sea ice. Atka Bay, Antarctica. June.