Eric Baccega / Black flat-coated retriever dog splashing in water and retrieving stick (Canis familiaris)

Mark Raycroft / Cocker Spaniel (Canis familiaris) puppy playing, North America

Mark Raycroft / Border Collie (Canis familiaris) adult with three tennis balls in its mouth, waiting to play fetch

Matthew Maran / Black and white border collie with stick, Hampstead Heath, England, UK, March.

Neil Aldridge / Spaniel gundog holding a dead female Ring-necked pheasant (Phasianus colchicus) in its mouth during a winter shoot on shooting estate, southern England, UK. January.

Neil Aldridge / Wet labrador gundog emerging from lake with a male Ring-necked pheasant (Phasianus colchicus) in its mouth during a winter shoot on shooting estate, southern England, UK. January.

Neil Aldridge / Spaniel gundog hauling itself out of a lake carrying a dead female Ring-necked pheasant (Phasianus colchicus) shot during a winter country shoot on shooting estate, southern England, UK. January.

Lynn M Stone / Labrador Retriever retrieving toy from sea, Guilford, Connecticut, USA

Ernie Janes / Yellow Labrador playing on a Norfolk beach, retrieving ball from sea, East Anglia, England, UK, December.

Ernie Janes / Yellow Labrador playing on a Norfolk beach, retrieving ball from sea, East Anglia, England, UK, December.

Eric Baccega / Black flat-coated retriever dog splashing in water and retrieving stick (Canis familiaris)

Ernie Janes / Cocker spaniel retrieving a shot Common pheasant (Phasianus colchicus), Norfolk, England, UK, December.

Ernie Janes / Cocker spaniel retrieving a shot Red-legged partridge (Alectoris rufa), Norfolk, England, UK, December.

Ernie Janes / Yellow labrador retrieving a shot Common pheasant (Phasianus colchicus), Norfolk, England, UK, December.

Norma Brazendale / Labrador retriever dog running through shallow water, River Mersey, England, UK, August 2013.

Roland Seitre / Man and woman in Ishaqbini Reserve, returning from fetching fire wood. Man carrying axe, woman the wood. Kenya, 2009.

Ernie Janes / Jack Russell Terrier retrieving stick from water, UK

Ernie Janes / Yellow Labrador retriever fetching ball from sea water, Norfolk, UK, March

Ernie Janes / Border collie running along beach with ball in its mouth, Norfolk, UK, October

Bryan and Cherry Alexander / Dogon women fetching water in earthenware jars, each holding 25 litres. Mali, West Africa, 1981.

Pete Oxford / Rajasthani man fetching water and preparing for the day at the Pushkar camel and livestock fair, Pushkar, Rajasthan, India, October 2006

Mark Raycroft / Weimaraner (Canis familiaris) puppy playing with stick, North America

Mark Raycroft / Weimaraner (Canis familiaris) puppy playing with stick, North America

Mark Raycroft / Golden Retriever (Canis familiaris) female puppy playing with stick, North America

Mark Raycroft / Beagle (Canis familiaris) puppy playing with stick, North America

Mark Raycroft / Beagle (Canis familiaris) puppies playing with stick, North America

Mark Raycroft / Beagle (Canis familiaris) puppy playing with stick, North America

Mark Raycroft / Beagle (Canis familiaris) puppies playing with stick, North America

Jaymi Heimbuch / Domestic Dog (Canis familiaris) named Ranger, a scent detection dog with Conservation Canines, playing in water, Adirondack Mountains, New York

Jaymi Heimbuch / Domestic Dog (Canis familiaris) named Scooby, a scent detection dog with Conservation Canines, playing during a break, northeast Washington

Mark Raycroft / Labrador Retriever (Canis familiaris) retrieving stick in snow

Mark Raycroft / Golden Retriever (Canis familiaris) fetching big stick in snow

Mark Raycroft / Chesapeake Bay Retriever (Canis familiaris) in wetland with bumper during training exercise

Mark Raycroft / Flat-coated Retriever (Canis familiaris) retrieving bumper in harvested corn field

Mark Raycroft / Doberman Pinscher (Canis familiaris) adult with clipped ears fetching stick at beach

Mark Raycroft / Shetland Sheepdog (Canis familiaris) adult fetching a ball in the snow

Mark Raycroft / Golden Retriever (Canis familiaris) adult running into lake to fetch a toy

Mark Raycroft / Golden Retriever (Canis familiaris) playing with a frisbee disc

Mark Raycroft / Golden Retriever (Canis familiaris) adult running into lake to fetch a toy

Mark Raycroft / Golden Retriever (Canis familiaris) adult running with a large stick

Mark Raycroft / Golden Retriever (Canis familiaris) adult running with a large stick

Mark Raycroft / Golden Retriever (Canis familiaris) fetching the newspaper

Mark Raycroft / Yellow Labrador Retriever (Canis familiaris) playing fetch with a tennis ball

Mark Raycroft / Yellow Labrador Retriever (Canis familiaris) playing fetch with a tennis ball

Mark Raycroft / German Shepherd (Canis familiaris) fetching a big stick

Norbert Wu / Domestic Dog (Canis familiaris) Yellow Labrador Retriever mix named Ange, fetching newspaper, California

Yves Lanceau / Domestic dog, Belgian Shepherd dog / Belgian Sheepdog / Tervueren, running with stick in mouth, France

Yves Lanceau / Labrador Retriever, yellow dog retrieving object from water, training, France