Siau Island Tarsier
The most endangered primate on an island that's been almost entirely cleared
No confirmed photograph exists
Location
Siau Island, North Sulawesi, Indonesia
Overview
The Siau Island tarsier is a tiny nocturnal primate — about 10 cm body, 25 g — with eyes proportionally the largest of any mammal. It cannot move its eyes; instead, it rotates its entire head up to 180 degrees, owl-style, to track prey. It was described as a distinct species only in 2008, from the 300 km² island of Siau in the North Sulawesi archipelago. By the time it was formally named, its island had been almost completely deforested for nutmeg and cloves. Surveys since its description have found almost nothing.
Why haven't we found it?
Siau is a small, heavily settled island. There is no vast unexplored interior. If the tarsier still exists, it is in tiny remnant forest patches — a few hectares at most — on steep volcano slopes. Camera traps deployed in likely areas after 2008 produced very few detections. The species may persist at extremely low numbers in fragments too small and fragmented for viable breeding.
Reasons to keep looking
- 1
Local reports from hunters and farmers in 2010–2012 described seeing large-eyed small primates in remnant forest patches near the island's volcanic spine.
- 2
The related Sulawesi tarsier has proven capable of surviving in small garden-edge habitats, suggesting some tarsier resilience to habitat degradation.
- 3
A small reforestation initiative on the island's northern slopes was established in 2016 with tarsier habitat in mind — local support suggests people on the island want it to survive.
Things worth knowing
- 1
Tarsiers are the only entirely carnivorous primates — they eat insects, lizards, and small birds. They cannot digest plant matter at all.
- 2
Their enormous eyes are fixed in the skull. Each eye is roughly the same size as the tarsier's brain. A human with proportionally equivalent eyes would have eyes the size of grapefruit.
- 3
They can hear ultrasound — up to 91 kHz — which likely helps them detect insect wing beats in the dark.
- 4
Siau Island sits on an active volcano. The species survived prehistoric eruptions, only to face near-extinction from 20th-century agriculture within decades.
- 5
In 2008, the IUCN listed it as one of the 25 Most Endangered Primates in the World — the same year it was formally described as a species.