Andy Rouse / Great crested grebe (Podiceps cristatus cristatus) courtship dance at dawn, Cardiff, UK, March. Highly Commended in the Animal Behaviour Category of the BWPA Competition 2015.

Andy Rouse / Great crested grebe (Podiceps cristatus cristatus) courtship dance Cardiff, UK, March.

Krijn Trimbos / Great crested grebe (Podiceps cristatus) pair in 'weed dance' courtship display, The Netherlands, March.

Krijn Trimbos / Great crested grebe (Podiceps cristatus) pair in 'weed dance' courtship display, The Netherlands. March.

Enrique Lopez-Tapia / Woman with lip plate, which signifies she is a married woman, Mursi tribe, Mago National Park. Ethiopia, November 20144

Laurent Geslin / Bride and groom at a modern orthodox christian wedding, Gondhar, North Ethiopia, 2006

Juergen Freund / A young Bajau woman with burak (face makeup), a paste made from pounded rice and tumeric which also serves as a natural sunblock. Wearing burak signifies the young lady is single and available for mar...

Juergen Freund / A young Bajau woman with burak (face makeup) looking at herself in a scrap of mirror. Burak is a paste made from pounded rice and tumeric and also serves as a natural sunblock. Wearing burak signifies...

Tony Heald / Man of the Toda tribe lifting a heavy stone to show he is ready for marriage. Nilgiri Mountains, Tamil Nadu, India. 2014.

Enrique Lopez-Tapia / Toraja wedding celebration. Toraja is an ethnic group in West and South Sulawesi. Tana Toraja, South Sulawesi, Indonesia. 2015.

Steve O. Taylor (GHF) / Guide holding gun, with wife in Guilemsi, Mauritania, 2004.

Steve O. Taylor (GHF) / Local guide with his wife wearing traditional clothes, central Mauritania, 2004.