Proboscis Simian

Explanation: On a klotok river boat voyage up the Sekonyer River in Tanjung Puting National Park, Borneo, Indonesia, we happened upon a small troop of massive-nosed simians, the proboscis monkey.

They were exploring and feeding in the mid-canopy of the riparian forest, lined with nypa palms (Nypa fruticans), a tropical coastal saline ecological equivalent to the baldcypress of southeast United States.

Endemic to Borneo, proboscis monkeys are largely associated with the riparian forests along rivers, islands, and coastal mangroves. They are IUCN-listed as Endangered with locally fragmented populations in decline. One reported threat is the conversion of coastal swamps to shrimp farms.

So why the long nose? It occurs essentially in the males, and is used as a resonating chamber for vocalizations. It may be important to keep their family unit intact, as the social unit is typically one male and 2 to 7 adult females. They may also vocalize to thwart predator attacks.

They are arboreal but also swim well. In the trees, they feed on leaves and fruits, as folivores and frugivores, as well as young leaves of mangroves and occasionally some invertebrates such as caterpillars and larvae.

Locally, they may be hunted for their meat, thought to be a delicacy. But populations on Borneo are under conservation protection status, although habitat conversion, impacts from large predatory cats, crocodiles, eagles, and other species, and poaching for black market sales, are all taking their toll.

EPOW - Ecology Picture of the Week