The aye-aye finds its food by sound. It scuttles along a branch tapping the wood up to eight times a second, listening for the hollow echo of a grub tunnel beneath the bark. When it hears one, it gnaws a hole with ever-growing front teeth and reaches in with its most extraordinary tool: a long, thin, almost skeletal middle finger that it uses to hook the grub out. No other primate hunts this way; the closest parallels are a few marsupials on the far side of the world. It is a marvel of evolution - and the very strangeness that fascinates biologists is what once doomed the animal among its human neighbors.

For centuries many Malagasy communities regarded the aye-aye as a harbinger of evil, an omen of death whose appearance near a village could mean a person was fated to die. Some held that the only way to lift the curse was to kill the animal on sight. Combined with the loss of its forest, that belief pushed the aye-aye toward extinction. So in the 1960s conservationists brought a small population to Nosy Mangabe, where the surrounding water and protected forest could shelter them. These were ancient fears, woven through generations of folklore, and the island was a way to give the animal a chance to survive while attitudes slowly changed.

Nosy Mangabe keeps human history too, etched literally in stone. On the island's west side, on a strand long known as the Plage des Hollandais - the Beach of the Dutchmen - more than forty inscriptions are carved into the shoreline boulders. They were cut between 1601 and 1657 by crews of the Dutch East India Company, who anchored in the sheltered bay to take on fresh water, mend their ships, and recover from sickness on the long haul to Southeast Asia. Researchers have identified the names of at least thirteen vessels, along with officers' names and the dates they arrived - a four-hundred-year-old guestbook scratched into rock by homesick sailors half a world from home.

The island has never had a permanent village; a simple campsite serves the biologists, researchers, and travelers who come to walk its forest trails. Besides the aye-aye, four other lemur species live here - the eastern woolly lemur, the white-fronted lemur, the black-and-white ruffed lemur, and the tiny gray mouse-lemur - along with the vulnerable Baron's climbing rosewood. In the 1980s the writer Douglas Adams came to Nosy Mangabe hunting a glimpse of the aye-aye for a radio series, and the visit became one of the strangest chapters of his book Last Chance to See. The reward for an overnight stay is the same one he sought: somewhere in the dark, that patient tapping, and a finger reaching into the wood.