Spectral tarsier in a tree. Spectral tarsiers (Tarsius tarsier) are found only in Indonesia. They are crepuscular (active at twilight) and nocturnal and are considered to be the most primitive of the modern tarsiers, lacking the adhesive toes common to other species. They also have the largest eye to body-size ratio of all mammals. Photographed in Tangkoko National Park, Northern Sulawesi, Indonesia.