Mark Raycroft / Australian Shepherd (Canis familiaris) in play posture

Mark Raycroft / Australian Shepherd (Canis familiaris) with blue eyes, bowing

Tui De Roy / Chinstrap Penguin (Pygoscelis antarctica) bowing over twin chicks Nelson Island, South Shetland Islands, Antarctica

Tui De Roy / Emperor Penguin (Aptenodytes forsteri) parents greeting chick, Atka Bay, Princess Martha Coast, Weddell Sea, Antarctica

Andy Rouse / Bengal tiger (Panthera tigris) cub. Ranthambhore National Park, India.

Stefan Christmann / Adelie penguin (Pygoscelis adeliae), pair in courtship. Atka Bay, Antarctica. February.

Nick Upton / Black-headed gull (Chroicocephalus ridibundus) pair courting on lake margin, calling and head bowing, Gloucestershire, UK, June.

Nick Upton / Mediterranean gull (Larus melanocephalus) pair courting on lake shore, walking in unison and head-bowing, Gloucestershire, UK, June

Ashley Cooper / Hawthorn tree (Crataegus monogyna) bent over by the prevailing wind on Humphrey Head Point above Morecambe Bay near Grange over Sands, England, UK. November 2006

Ashley Cooper / Hawthorn trees (Crataegus monogyna) bent over by the prevailing wind on Humphrey Head Point above Morecambe Bay , Grange over Sands, England, UK. November 2006

Nick Upton / Cream-coloured courser (Cursorius cursor) bowing during courtship in steppe scrubland, Jandia Natural Park, Fuerteventura, Canary Islands, May.

Konrad Wothe / Russet-backed oropendola (Psarocolius angustifrons) bowing display, Panguana Reserve, Huanuca Region, Peru.