Madagascar is home to a variety of primates, most notably lemurs. Lemurs are small, arboreal mammals that are native to the island of Madagascar and are the most threatened group of mammals in the world. They are characterized by their large eyes, long tails, and distinctive calls. There are over 100 species of lemurs, ranging from the smallest, the mouse lemur, to the largest, the indri. Lemurs play an important role in the ecology of Madagascar, as they are keystone species that help maintain the balance of the island's ecosystems.