What If Gone

Species → Bornean Orangutan

Bornean Orangutan

Pongo pygmaeus

between 55,000 and 104,000 individuals per the most recent estimates,…
Extinction risk Critically Endangered
Tropical forestSeed disperserCatastrophic declineExtinction
Bornean Orangutan (Pongo pygmaeus)
Photo: A.Baihaqi, Wikimedia Commons (CC BY-SA 4.0)

What if it disappeared?

Impact High
1 year

Without the orangutan, the large seeds that it alone, on this island, swallows whole stop being carried away: three-quarters of its analyzed feces contained intact seeds from 24 different plant genera, moved an average of 500 to 600 meters from the parent tree.

Documented
Detail

Blackburn, A., Susanto, T.W. & Knott, C.D. (2020). Orangutan seed dispersal in Gunung Palung National Park, Borneo, Indonesia: dispersal quantity, germination rates, gut transit times, and dispersal distances. 7th Frugivores and Seed Dispersal Symposium.

Study based on 549 fecal samples from 36 individuals at Gunung Palung National Park (Borneo). The orangutan is one of the only animals in Borneo large enough to swallow large-seeded fruit whole, on an island with neither elephants nor rhinoceroses to fill that role — which makes this transport hard to replace with another species the moment it stops.

10 years

From one fruiting season to the next, these seeds would now fall under their own parent tree instead of at a distance — and for five of the six genera tested, they would also germinate less well: seeds that passed through the orangutan's gut germinated significantly better than control seeds, an advantage that disappears along with it.

Extrapolated
Detail

Extrapolation à partir de Blackburn, Susanto & Knott (2020), qui mesure la distance de dispersion et l'avantage de germination lié au passage digestif sur les orangs-outans actuellement présents, sans suivre ce qui arrive au recrutement des jeunes arbres une fois l'espèce disparue.

The study establishes two directly measured facts — seed transport distance and the germination boost from gut passage — but not their combined effect across multiple fruiting seasons. In tropical forest, seeds falling near the parent tree typically face higher mortality from predation and competition; combined with already weaker germination without gut passage, recruitment of the affected tree species would likely decline year after year.

What's missing to confirm it: No monitoring of actual tree seedling recruitment has been carried out across multiple seasons to confirm that the loss of dispersal and germination really does translate into fewer established saplings, rather than being offset by other dispersers.

100 years

In areas where the orangutan has been gone since the 1950s — nearly a century in some places already — regeneration of large-seeded tree species would likely be measurably slower than in forests where it still persists; but in a landscape so extensively converted to plantations, this effect would remain hard to separate from the far larger one of the forest itself disappearing.

Hypothesis
1000 years

Over a thousand years, with no other animal on the island large enough to swallow these fruits whole, the tree species that depended on the orangutan would likely be permanently disadvantaged against those dispersed by other means — a lasting imbalance in forest composition that would probably never quite correct itself, even if the forest itself eventually regrew elsewhere.

Hypothesis

Documentation

Last verified: August 16, 2026