They don't walk, and they aren't really dead. But these snails are zombies. They have been hijacked by parasites that control their brains and movements. It's a clever ploy to help the parasites' offspring spread and endure.

Beneath this peaceful landscape...a snail has eaten parasites that've turned it into a zombie.

These spectacular...bizarre...bulging eyeballs...are the snail's tentacles.

Inside them, parasitic worms have begun an amazing feat of mind control.

These parasites have taken over the snail's tentacles...and its brain.

It's all part of an ingenious plan to extend the life of the parasite...and its offspring.

The snail has become possessed.

It is doomed now to follow the parasite's will...and the parasite is on the move...looking for another host.

Next, the parasite needs a bird.

Hypnotized...the snails march into the sunshine.

They climb from the shade...to the tips of exposed branches above.

The snail's tentacles...engorged now by their possessors...have grown to resemble a maggot.

And a maggot is the favorite food of the birds above.

In an instant...the bird attacks...and the parasite triumphs.

The parasitic worm happily multiplies in the bird's stomach.

Its final trick is to complete the cycle.

But it will have little trouble...as the snails below graze on bird droppings...filled with a new batch of mind-controlling parasites.

Once they're eaten...the hypnosis of the snails will continue...and the life cycle of the parasite...will roll on!