Fiona Rogers / Eastern Chimpanzee (Pan troglodytes schweinfurthii) five year old juvenile female, named Fadhila, playing with her three year old brother, named Fifty, Gombe National Park, Tanzania

Edwin Giesbers / Close-up of a litter of Wild boar (Sus scrofa) piglets sleeping on top of their mother, with another piglet joining, Germany, January. Captive.

Edwin Giesbers / Close-up of a litter of Wild boar (Sus scrofa) piglets sleeping on top of their mother, with another piglet joining, Germany, January. Captive.

Edwin Giesbers / Close-up of a litter of Wild boar (Sus scrofa) piglets sleeping on top of their mother, Germany, January. Captive.

Brian Bevan / Grey seal (Halichoerus grypus) pup trying to suckle, Norfolk, England, UK, January.

Frederique Olivier / Young Burchell's zebra (Equus burchellii) playing, biting and kicking its mother, Serengeti NP, Tanzania.

Thomas Marent / Saddle-back Tamarin (Saguinus fuscicollis) mother with young, Tambopata-Candamo Nature Reserve, Peru

Suzi Eszterhas / Proboscis Monkey (Nasalis larvatus) mother nursing four month old baby, Sabah, Borneo, Malaysia

Andy Rouse / Bengal tiger (Panthera tigris tigris) female 'T19 Krishna' carrying 2 month cub, Ranthambhore National Park, India.

Suzi Eszterhas / Capybara (Hydrochoerus hydrochaeris) mother nursing young, Pantanal, Brazil

Matthias Breiter / Polar Bear (Ursus maritimus) mother and three-month-old cubs, Wapusk National Park, Manitoba, Canada

David Pattyn / Little Grebe (Tachybaptus ruficollis) female sleeping with one of her 28 day chicks. The Netherlands, June.