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.

Mark Raycroft / Black Labrador Retriever (Canis familiaris) puppy sniffing flower

Mark Raycroft / English Bulldog (Canis familiaris) female running

Mark Raycroft / Beagle (Canis familiaris) puppy smelling tulip

Pal Hermansen / Domestic reindeer herd (Rangifer tarandus) group close together in enclosure, Oppland, Norway, September 2014.

Mark Taylor / Black and white Jack-a-poo, Jack Russell cross Poodle, pup, 8 weeks old, jumping up.

Jane Burton / British Shorthair kittens, Benedict, ginger, and Joan, silver tabby.

Mark Taylor / Black-and-white kitten, Loona, age 11 weeks, arching back.