How can removing large predators cause smaller carnivore populations to increase?

The phenomenon where populations of medium-sized predators increase following the removal of top carnivores is known as mesopredator release.

This occurs because top carnivores—such as wolves and cougars—typically suppress mesopredator populations through three primary mechanisms:

• Direct Predation: Top carnivores often kill and consume mesopredators, acting as a direct source of mortality.12
• Competition: Mesopredators compete with top carnivores for the same food, den sites, and hunting grounds. Because they are often outcompeted, mesopredators are forced to avoid areas occupied by top carnivores or alter their foraging patterns to minimize encounters.12
• Resource Availability: When top carnivores are removed, these previously restricted resources become available, allowing mesopredator populations to expand rapidly into new territories.12

This shift can trigger a trophic cascade, where the resulting surge in mesopredators places intense pressure on their own prey, such as songbirds and small mammals, often leading to a decline in overall biodiversity.12