Steven Kazlowski / Polar bear (Ursus maritimus) pair of adult sows play with one another on the pack ice during fall freeze up, 1002 area of the Arctic National Wildlife Refuge, North Slope, Alaska, USA

Anup Shah / African lion (Panthera leo) cubs aged about 24 months play fighting, Masai Mara National Reserve, Kenya, September

Tony Heald / African lion (Panthera leo) two young males playfighting, Etosha National Park, Namibia

Merryn Thomas / Two dogs playfighting on the coast. St. Martin's. Maisie (3/4 Tibetan Terrier, 1/4 Cocker Spaniel) and Gonzo (1/2 Tibetan, 1/2 Cocker). Isles of Scilly, Cornwall, UK, January 2012.

Mary McDonald / Dhole / Asiatic Wild Dog (Cuon alpinus) playfighting. Satpura National Park, Madhya Pradesh, India.

Ann & Steve Toon / Chacma baboons (Papio ursinus) two young playfighting within troop, Kruger National Park, South Africa, May.

Ann & Steve Toon / Baby chacma baboons (Papio ursinus) two young playfighting, Kruger National Park, South Africa, May.

Steven Kazlowski / Polar bear (Ursus maritimus) pair of spring cubs play on newly formed pack ice along the arctic coast in autum, 1002 area of the Arctic National Wildlife Refuge, Alaska, Beaufort Sea, USA, sequence 2/...

Steven Kazlowski / Polar bear (Ursus maritimus) pair of spring cubs play on newly formed pack ice along the arctic coast in autum, 1002 area of the Arctic National Wildlife Refuge, Alaska, Beaufort Sea, USA, sequence 3/...

Steven Kazlowski / Polar bear (Ursus maritimus) pair of spring cubs play on newly formed pack ice along the arctic coast in autum, 1002 area of the Arctic National Wildlife Refuge, Alaska, Beaufort Sea, USA, sequence 1/...

Andrew Parkinson / Red fox (Vulpes vulpes) two cubs playfighting on the fringes of a field, Derbyshire, UK, June.

Kristel Richard / Konik horses (Equus caballus) - Two wild Konik young colts playfighting, Millingerwaard nature reserve, Netherlands, April