David Attenborough presents a nature documentary series looking at why mammals are the most successful creatures on the planet.

The story follows the sometimes happy, sometimes sad, and a tad stressful daily life of "some sort of small, cute creature" (Nanka Chiisakute Kawaii Yatsu) known as Chiikawa. Chiikawa enjoys delicious food with bees and rabbits, toils hard every day for the rewards of work, and still maintains a smile.

Walking With Prehistoric Beasts explores how life on earth first began. Using real footage, the series goes inside the body of our monster ancestors. For the first time, morphing technology is used to reveal how our ancestors evolved.

More than four years of filming have been necessary to capture the impressive images of the most varied animal species that inhabit the Iberian Peninsula: amphibians, reptiles, mammals, birds, insects and fish are represented in this wonderful journey through the different ecosystems that we can find in Iberian lands.

Latest research has revealed that first mammals and first dinosaurs appeared on earth at about the same time and that the ancestral mammals underwent dramatic evolution while challenging the dinosaurs. It was these struggles that created the basic nature of all present mammals, including humans.