Carol Walker / Mustang herd standing in snow. Black Hills Wild Horse Sanctuary, South Dakota, USA. January 2017.

Klein & Hubert / Mustang stallion kicking out after winning fight. Rocky Mountains, USA, June.

Klein & Hubert / Mustang horses, chestnut painted overo mare and her buckskin daughter, age two years, Nevada, USA.

Klein & Hubert / Dun foal jumping over a palomino yearling while playing. Nevada, USA.

Nick Upton / New Forest pony (Equus caballus) grazing grassland around Green Pond, Fritham Plain, New Forest, Hampshire, UK. October.

Nick Upton / New Forest ponies (Equus caballus) grazing heathland, Nomansland, New Forest, Hampshire, UK. October.

Nick Upton / New Forest ponies (Equus caballus) grazing grassland around Green Pond, Fritham Plain, New Forest, Hampshire, UK. October.

Olga Kamenskaya / Wild horses mare and foal, Lake Teletskoye. Altai Nature Reserve, Altai Republic, Russia

Olga Kamenskaya / Wild horses at edge of lake, Lake Teletskoye. Altai Nature Reserve, Altai Republic, Russia

Olga Kamenskaya / Wild horses, foal and mare, Lake Teletskoye. Altai Nature Reserve, Altai Republic, Russia

Carol Walker / Wild grey stallion, bay mare and bay foal all in one family move together on a hill in the Red Desert Complex, Wyoming, USA. August.

Carol Walker / Black and white image of wild bay stallion, McCullough Peaks Herd Management Area, Wyoming, USA, July.

Carol Walker / Wild varnish roan stallion, leaps as he escapes after he was released, during the Red Desert Complex Roundup, Wyoming, USA. October.

Carol Walker / Wild leopard appaloosa stallion, running at dawn in the Red Desert Complex, Wyoming, USA.

Carol Walker / Wild horse stallion, a blue pinto roan, portrait. Red Desert Complex, Wyoming, USA.

Staffan Widstrand / Wild-living Konik horses, (Equus caballus) foal, Oostvaardersplassen Nature Reserve, The Netherlands, April

Staffan Widstrand / Wild-living Konik horses, (Equus caballus), foal running, Oostvaardersplassen Nature Reserve, The Netherlands, April

Staffan Widstrand / Wild-living Konik horses, (Equus caballus) mare with her foal, Oostvaardersplassen Nature Reserve, The Netherlands, April

Staffan Widstrand / Wild-living Konik horses, (Equus caballus), fighting, Oostvaardersplassen Nature Reserve, The Netherlands, April

Staffan Widstrand / Wild-living Konik horse, (Equus caballus) rolling in dirt, Oostvaardersplassen Nature Reserve, The Netherlands, April

Staffan Widstrand / Wild-living Konik horse (Equus caballus), flehmen response, Oostvaardersplassen Nature Reserve, The Netherlands, April

Staffan Widstrand / Wild-living Konik horses, (Equus caballus), Oostvaardersplassen Nature Reserve, The Netherlands, April

Carol Walker / Mustang herd standing in grassland. Red Desert Complex, Wyoming, USA. September.

Carol Walker / Sable Island horse, wild stallion rolling on back on beach, wildflowers in background. Sable Island National Park, Nova Scotia, Canada. July.

Carol Walker / RF - Mustang herd standing in grassland, foal lying on ground. Red Desert Complex, Wyoming, USA. September. (This image may be licensed either as rights managed or royalty free.)

Carol Walker / RF - Wild Pinto horse stallion rearing up on back legs in grassland, with snow covered mountains in background. McCullough Peaks Herd Management Area, Wyoming, USA. April. (This image may be licensed...

Carol Walker / Wild Pinto horse, two stallions rearing up on hind legs in grassland. McCullough Peaks Herd Management Area, Wyoming, USA. April. (This image may be licensed either as rights managed or royalty free.)

Carol Walker / Sable Island horse, group of wild horses including foal at waterhole. Sable Island National Park, Nova Scotia, Canada. September.

Carol Walker / RF - Wild Dulmen pony herd including female and foal. Germany. (This image may be licensed either as rights managed or royalty free.)

Carol Walker / Mustang mare and foal nuzzling. Red Desert Complex, Wyoming, USA. June.

Carol Walker / RF - Mustang horse, two stallions rearing up in aggression, in grassland. McCullough Peaks Herd Management Area, Wyoming, USA. April. (This image may be licensed either as rights managed or royalty fr...

Carol Walker / RF - Mustang mare and foal standing in front of water body. Red Desert Complex, Wyoming. July. (This image may be licensed either as rights managed or royalty free.)

Carol Walker / Dulmen pony, wild mare and foal nuzzling. Germany.

Carol Walker / Mustang mare with blue roan colouration, standing in grassland. Salt Wells Creek Herd, Wyoming, USA. October.

Carol Walker / Mustang stallion running, blue roan colouring. McCullough Peaks herd, Northern Wyoming, USA.

Carol Walker / Mustang stallion with blue roan colouring, portrait. McCullough Peaks herd, Northern Wyoming, USA.

Carol Walker / RF - Mustang stallion and his colt, colt opening and closing mouth in submission. Sand Wash Basin Herd Management Area, Colorado, USA. (This image may be licensed either as rights managed or royalty f...

Carol Walker / Mustang horse, two, one with skewbald colouration. Sand Wash Basin Herd Management Area, Colorado, USA.

Carol Walker / Mustang with grey colouration. Sand Wash Basin Herd Management Area, Colorado, USA.

Carol Walker / Mustang horses, two drinking, reflected in water. Sand Wash Basin Herd Management Area, Colorado, USA.

Carol Walker / Mustang foal standing amongst herd. Sand Wash Basin Herd Management Area, Colorado, USA.

Carol Walker / Mustang horse, dun mare and blue roan foal nuzzling. Sand Wash Basin Herd Management Area, Colorado, USA.

Carol Walker / RF - Mustang horse, dun mare and blue roan foal nuzzling. Sand Wash Basin Herd Management Area, Colorado, USA. (This image may be licensed either as rights managed or royalty free.)

Carol Walker / Mustang herd including mares and foals, in evening light. Salt Wells Creek Herd Management Area, Wyoming, USA. July 2016.

Carol Walker / Mustang mare and foal with skewbald colouration. South Steens Wild Horse Herd, Oregon, USA. June.

Carol Walker / Mustang horse herd at waterhole, mountains in background. Onaqui Mountain Wild Horse Management Area, Utah, USA. July 2018.

Carol Walker / RF - Mustang herd running up a hill. Fifteenmile Herd Management Area, Wyoming, USA. July. (This image may be licensed either as rights managed or royalty free.)

Carol Walker / Sable Island horses, two wild stallions greeting, head to head . Sable Island National Park, Nova Scotia, Canada.