Doc White / Humpback whale (Megaptera novaeangliae) group bubble-netting in coastal waters. Southeast Alaska, USA. June.

David Fleetham / Humpback whale (Megaptera novaeangliae), close up on tubercles on underside of chin. Hawaii.

David Fleetham / Humpback whale (Megaptera novaeangliae) spyhopping, close up on tubercles on underside of chin. Hawaii.

Edwin Giesbers / Orang utan (Pongo pygmaeus) close-up of mouth of dominant male called Aman. Matang wildlife centre, Sarawak, Borneo, Malaysia, June 2010. Endangered

Petra Wegner / Pug lying on a rug next to a mixed breed dog with their chins on the floor.

Jane Burton / Yellow and Chocolate Labrador Retriever pups lying down with chins on the floor.

Jane Burton / Yellow and Chocolate Labrador Retriever pups lying down together, chins on the floor

Jane Burton / Two Brittany Spaniel pups asleep with chins on floor.

Laurie Hedges / Chimpanzee (Pan troglodytes) male scratching forearm and chin whilst standing on tree branch, Nyungwe National Park, Rwanda, July. Endangered.

Roland Seitre / Indo-Chinese box turtle (Cuora galbinifrons) close up of chin and neck. Captive, native to China, Vietnam and Laos. Germany.

Nick Upton / Four Northern pintail (Anas acuta) males following a female in flight, with some raising their chins and "burp" calling in courtship display, Gloucestershire, UK. November.

Pal Hermansen / RF - Red squirrel (Sciurus vulgaris) against sky, view from below. Akershus, Viken, Norway. April. (This image may be licensed either as rights managed or royalty free.)