How can invasive predators reduce native prey populations?

Invasive predators can significantly reduce native prey populations by introducing intense, novel predation pressure to an ecosystem that lacks natural defenses against them. Because these predators often possess a competitive advantage—such as being highly adept at capturing prey—they can cause native populations to decline rapidly, sometimes leading to localized extinction.12

The mechanisms by which this occurs include:

• Direct Predation: Invasive predators, such as the brown tree snake on Pacific islands or feral cats in various habitats, consume native birds, reptiles, and amphibians that have not evolved to recognize or evade them.23
• Trophic Cascades: The introduction of a new predator can trigger a trophic cascade, where the predator decimates primary prey, causing ripple effects throughout the food web. Conversely, the removal of top predators can lead to "mesopredator release," where medium-sized invasive predators increase in number and further suppress native prey.4
• Competitive Displacement: Beyond direct consumption, invasive predators may outcompete native species for limited resources, further stressing populations already struggling to survive.15

These impacts are particularly severe on isolated islands or in ecosystems where native species have evolved in the absence of such predators.16