Jack Dykinga / Storm clouds at sunset over balancing eroded boulder, Texas Canyon, Little Dragoon Mountains, Chihuahuan Desert, Arizona, USA. September.

Jan Wegener/ BIA / Grey Heron (Ardea cinerea) spreading wings on frozen lake, Berlin, Germany

Alain Ghignone/ BIA / Montagu's Harrier (Circus pygargus) male landing, Andalusia, Spain

Jan Wegener/ BIA / Horsfield's Bronze-Cuckoo (Chrysococcyx basalis) balancing, Victoria, Australia

Steven Kazlowski,Steven Kazlowski / Polar bear (Ursus maritimus) juvenile spreading body weight over thin newly forming pack ice, trying not to break through, Beaufort Sea, off the 1002 area of the Arctic National Wildlife Refuge, North...

Staffan Widstrand / Ringed seal (Pusa hispida) hauled out on rock, Svalbard, Norway

Fiona Rogers / Western lowland gorilla (Gorilla gorilla gorilla) juvenile male 'Tembo' aged 4 years crossing a river bi-pedally, Bai Hokou, Dzanga Sangha Special Dense Forest Reserve, Central African Republic. Decem...

Roland Seitre / Greater Egyptian Jerboa (Jerboa orientalis) balancing using its tail. Captive. Endemic Algeria to Saudi Arabia.

George Sanker / Black Bear (Ursus americanus) cub balancing on branch in tree, Yellowstone NP, Wyoming, USA

George Sanker / Least Chipmunk (Tamius minimus) feeding on the seeds of a thistle bush during a snowstorm, Grand Teton NP, Wyoming, USA, October

Mark Bowler / Shetland pony (Equus caballus) foal, UK

Jeff Wilson / Field Assistant, Jason Roberts, standing on top of rock pinnacle, Svalbard, Spitzbergen, Norway, July 2009, Taken on location for the BBC series, Frozen Planet.