Eric Baccega / Chimpanzee (Pan troglodytes) juvenile male aged 10 years, portrait. Beauval Zoo Parc, France. Captive.

SCOTLAND: The Big Picture / Common toad (Bufo bufo) standing on fallen tree over river, Atlantic rainforest, Glen Nant, Scotland, UK, September.

SCOTLAND: The Big Picture / Mountain hare (Lepus timidus) on all fours in upland habitat with forest and mountain in background, Deeside, Cairngorms National Park, Scotland, UK, March 2016.

Sandesh Kadur / Arunachal macaque (Macaca munzala) Tawang, Arunachal Pradesh, India. Endangered species.

Fergus Gill / Grey squirrel (Sciurus carolinensis) looking alert, on all fours, in an urban park in winter. Glasgow, Scotland, Dec .

Pete Oxford / Barbary Macaque (Macaca sylvanus) walking on all fours, Gibraltar, United Kingdom

Anup Shah / Verreaux's sifaka (Propithecus verreauxi) crouching on all fours, Berenty Private Reserve, Madagascar, October

Suzi Eszterhas / Proboscis monkey (Nasalis larvatus) sub-adult standing on all-fours in tree. Tanjung Puting National Park, Indonesia.