Carol Walker / Two wild pinto Mustang stallions battle for dominance in Sand Wash Basin, Colorado, USA.

Carol Walker / Wild pinto Mustang mare and foal running in Sand Wash Basin, Colorado, USA.

Carol Walker / Head portrait of grey Arabian stallion running in desert dunes near Dubai, United Arab Emirates.

Carol Walker / Two wild Mustang stallions fighting in the White Mountain Herd Area, Wyoming, USA. August.

Carol Walker / Two white Camargue horses in ocean of Camargue, France, Europe. May.

Carol Walker / Wild Mustang horse rearing, Pryor mountains, Montana, USA. June.

Kirkendall-Spring / View over the Campbell Lakes with stormy clouds at dusk, viewed from Walker Valley Overlook in Hart Mountain National Antelope Refuge, Oregon, USA, May 2013.

Juergen Freund / Non-diver tourists surrounded by fish, trying out the sea walker from the Sunlover Pontoon, Great Barrier Reef, Queenland, Australia, November 2012

Oriol Alamany / Hiker walking the Calanche de Piana, Corse-du-Sud, Corsica Island, France, Model released.

Carol Walker / Friesian horse, black stallion running in field, Livingston, Montana, USA

Carol Walker / Girl stroking donkey (Equus asinus) New Mexico, USA, September 2011, model released

Carol Walker / Lusitano horse, bull fighter mounted on grey stallion, in this type of bull fighting neither horse nor bull are injured, Portugal, May 2011, model released