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 / 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.

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.

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.

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