Episode Two: Insect Hunters

When mammals first appeared, insects were abundant on earth, and mammals made meals of them. Crucially, they were the first creatures able to make and regulate their own body heat, so they could hunt insects in the cool of the night, when most of the predatory dinosaurs were asleep. The modern musk shrew gives us an insight into how these first mammals might have lived.

After the dinosaurs so suddenly disappeared, the mammals were free to conquer new territories. We meet shrews that dive under water, moles that swim in sand, and extraordinary creatures that gather their prey by running at speed down trail systems above and below ground.

It's hard to sustain a large body by catching insects one by one but about 50 million years ago, some of them broadened their diet. The hedgehogs and armadillos mix their insects with fruit and birds eggs.

Halfway through the history of the mammals, insects started to build huge nests, protected with walls of baked mud -- these were impenetrable to any creature of the time. But with pangolins and giant anteaters, the mammals rose to the challenge. These spectacular animals survive entirely on a diet of social ants and termites -- they have the biggest claws of any mammals, long tongues and the ability to protect themselves against angry insects and large predators.

But many of the insects could fly and were out of reach for ground dwelling mammals. But way back in mammalian history -- probably when the dinosaurs still roamed -- one mammal took to the air. Today, the earth holds a bewildering array of insect eating bats. We even meet one -- the Natterers bat -- that can take spiders from their webs without becoming tangled in the silk. And another, in New Zealand, that has retraced it's origins and returned to the ground to forage like a shrew. The insect eating mammals were there at the very beginning of the mammal's and are still thriving today, they are one of the great success stories in The Life of Mammals.