This is the story of two young animals forced to grow up fast. In Africa's savannah, a baby elephant shrew learns how speed is the secret to survival amongst the largest animals on Earth; and in America, a young grasshopper mouse confronts the Wild West's deadliest creatures to stake a claim of his own.

In the wild and ancient woods of North America, a young chipmunk is gathering a vital store of nuts ahead of his first winter - but in his way are countless, ruthless rivals and hungry giant predators.

[Season Finale] This is the ultimate hidden kingdom - the urban jungle. In the futuristic metropolis of Tokyo, a rhinoceros beetle escapes his captors and begins an extraordinary journey through this alien world to find sanctuary.