Danny Green / Reindeer (Rangifer tarandus), two play fighting in snow. Svalbard, Norway, April.

Danny Green / Polar bear (Ursus maritimus), two cubs playing, leaping across sea ice, reflected in water. Svalbard, Norway, July.

Ann & Steve Toon / African elephants (Loxodonta africana) herd silhouetted at sunset. Chobe National Park, Botswana.

Alex Mustard / Spinner dolphin (Stenella longirostris) pod socialising close to surface. Fury Shoal, Sataya Reef, Marsa Alam, Egypt.

Felis Images / Asiatic lion (Panthera leo persica), female and cubs in morning light, cub biting mother's leg. Gir National Park, Gujarat, India. Photo Phillip Ross/Felis Images

Tony Wu / Humpback whale (Megaptera novaeangliae australis) male calf playing at ocean surface after coming up to breathe. Vava'u Islands, Tonga.

Tony Heald / Elephant (Loxodonta africana) babies playing, Etosha National Park,Namibia.

Staffan Widstrand / African bush elephant, (Loxodonta africana) two head to head playing, Zimanga Private Nature Reserve, KwaZulu Natal, South Africa

Andy Rouse / Bengal Tiger (Panthera tigris) family drinking from pool, Ranthambhore, India

Alex Mustard / Grey seal (Halichoerus grypus) young female opens her mouth and blows bubbles through her nose playfully while she looks up from the seabed. Lundy Island, Devon, UK, Bristol Channel. August. Highly co...

Alex Mustard / Grey seal (Halichoerus grypus) playful young seal above a kelp forest. Lundy Island, Devon, UK Bristol Channel, August

Doug Perrine / Bottlenose dolphin (Tursiops truncatus) swimming with a pair of Humpback whales (Megaptera novaeangliae) Kona, Hawaii, USA