- [Narrator] Water shrews are the cheetahs of the wetlands.

Water shrews have the highest metabolism of any diving mammal.

They seldom go more than a few hours without a meal and this shrew hasn't eaten all morning.

The edge of the stream provides some rewards, but he'll need more than an insect carcass to satisfy his appetite.

His favorite meals are found just below the water's surface.

As the smallest diving mammal on earth, hunting for this shrew lasts just a few seconds.

But what happens underwater is remarkable.

Because of his poor eyesight, he must rely on a complex hunting strategy.

He scans the surface to detect the slightest break in the water.

Then he forages along the bottom trying to shake loose his prey.

When his long whiskers detect movement, he gives chase.

Crayfish can be elusive and they're also half his size.

But with reflexes 10 times faster than our own, he eventually outpaces them.

Slower prey like these dragonfly nymphs, waiting in ambush for their own meal, rely on stealth to remain undetected.

To find the camouflaged nymphs, he uses a rare superpower, the ability to sniff out prey underwater.

By blowing tiny bubbles of air, he can detect the scent particles in the water.

But even with his advanced arsenal, hunting often turns into an elaborate game of hide and seek.

But once the shrew locks onto its prey, it rarely escapes.