Suzi Eszterhas / Proboscis Monkey (Nasalis larvatus) three month old baby in tree, Sabah, Borneo, Malaysia

Theo Webb / Bengal Tiger (Panthera tigris) six month old cub jumping on its mother, Bandhavgarh National Park, India.

Fiona Rogers / Silvered Leaf Monkey (Trachypithecus cristatus) mother with five month old baby, Bako National Park, Sarawak, Borneo, Malaysia

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

Cyril Ruoso / Mountain Gorilla (Gorilla gorilla beringei) female with her three month old newborn, Parc National Des Volcans, Rwanda

Suzi Eszterhas / Mountain Gorilla (Gorilla gorilla beringei) mother holding five month old twin babies, Parc National des Volcans, Rwanda

Suzi Eszterhas / Mountain Gorilla (Gorilla gorilla beringei) mother holding five month old twin babies, Parc National des Volcans, Rwanda

Colin Varndell / Three month old Red fox (Vulpes vulpes) cub walking through meadow, Dorset, England, UK June

Suzi Eszterhas / Polar Bear (Ursus maritimus) three to four month old cub peeking over mother's body while she is tranquilized by researchers, vulnerable, Wapusk National Park, Manitoba, Canada

Matthias Breiter / Polar Bear (Ursus maritimus) three month old cub looking out of its birth den, vulnerable, Wapusk National Park, Manitoba, Canada

Yva Momatiuk & John Eastcott / Grizzly Bear (Ursus arctos horribilis) 4 month old cubs trying to engage mother in play, Katmai National Park, Alaska

Yva Momatiuk & John Eastcott / Grizzly Bear (Ursus arctos horribilis) 4 month old cubs trying to engage mother in play, Katmai National Park, Alaska