Which island has the greatest number of unique mammal species?

Luzon Island, in the Philippines has the greatest number of unique animal species.

Explanation:

Researchers have shown that out of 56 species of non-flying mammal species that are now known to live on the island, 52 live nowhere else in the world. Of those 56 species, 28 were discovered during the course of the project. Nineteen of the species have been formally described in scientific journals, and nine are currently "in the works." Currently 93% of the island's land land mammals have been found no where else.