What If Gone

Species → Jaguar

Jaguar

Panthera onca

173,000 individuals
Extinction risk Near Threatened
Apex predatorTropical forestMesopredator releaseMegafauna
Jaguar (Panthera onca)
Photo: Bernard DUPONT, Wikimedia Commons (CC BY-SA 2.0)

What if it disappeared?

Impact High
1 year

On small forested islands cut off from the mainland by the flooding of a dam — and thus inaccessible to large cats like the jaguar and puma — densities of howler monkeys, iguanas, leaf-cutter ants, and rodents climbed to 10 to 100 times their level on the neighboring mainland.

Documented
Detail

Terborgh, J., Lopez, L., Nuñez, P. et al. (2001). Ecological Meltdown in Predator-Free Forest Fragments. Science, 294(5548), 1923–1926.

The 1986 flooding of the Guri Dam turned hilltops into isolated forest islands, too small for large cats and other vertebrate predators to persist on. Freed from this control, herbivores and small generalist predators proliferated to densities the authors describe as "hyperabundant."

10 years

This herbivore explosion eventually rippled through the forest itself: on the most affected islands, recruitment of young canopy trees dropped by roughly 80% relative to normal.

Documented
Detail

Terborgh, J., Feeley, K., Silman, M., Asner, G. et Diaz, S. (2006). Vegetation dynamics of predator-free land-bridge islands. Journal of Ecology, 94(2), 253–263.

Longer-term vegetation monitoring confirms that the cascade triggered by the absence of predators does not stop at herbivore populations: it propagates all the way to the regeneration of the forest canopy itself, with a collapse in young tree recruitment on the islands most densely populated with howler monkeys and leaf-cutter ants.

100 years

Over a century without jaguars anywhere on the mainland — not just on small isolated islands like at Lake Guri — medium-sized predators such as the puma would likely take over part of its role, softening the extreme explosion seen on the islands; but across such a vast territory, canopy regeneration would probably still lag in places, without ever matching the total-isolation conditions that produced the collapse measured at Lake Guri.

Hypothesis
1000 years

Over a thousand years, it would no longer be just the number of young trees that suffered, but their mix: tree species most sought after by howler monkeys and rodents would consistently have less chance of establishing than less-favored ones, gradually reshaping the canopy's species composition — a forest that likely would never quite return to the same mix, even if the jaguar came back.

Hypothesis

Documentation

Last verified: August 16, 2026

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