Linking a cougar decline, trophic cascade, and catastrophic regime shift in Zion

Ripple and Beschta documented a striking felid-driven trophic cascade by contrasting heavily visited Zion Canyon, where human presence depressed cougars, with a nearby low-visitation canyon where cougars remained. Where cougars were scarce, mule deer were abundant and browsed cottonwoods heavily, leading to bank erosion and declines in riparian vegetation, amphibians, lizards and butterflies; where cougars persisted, deer were fewer and the riparian system flourished. The study provided field evidence that an ambush felid can structure entire stream ecosystems through both direct predation and fear-mediated effects on deer. It became a touchstone for the role of pumas as keystone predators and for the broader debate over large-carnivore trophic cascades.