Echoes of the late Pleistocene in a novel trophic cascade between cougars and feral donkeys

Introduced large herbivores have partly filled ecological gaps formed in the late Pleistocene, when many of the Earths megafauna were driven extinct. However, surviving predators are widely considered unable to influence introduced megafauna, leading them to exert unusually strong herbivory and disturbance-related effects. We report on a behaviorally-mediated trophic cascade between cougars (Puma concolor) and feral donkeys (Equus africanus asinus) at desert wetlands in North America. In response to predation of juveniles, donkeys shifted from nocturnal to almost exclusively diurnal, thereby avoiding peaks in cougar activity. Furthermore, donkeys reduced the time they spent at desert wetlands by 87%: from 5.5 hours a day to 0.7 hours at sites with predation. These shifts in activity were associated with increased activity and richness of other mammal species and reduced disturbance and herbivory-related effects on these ecologically-distinct wetland ecosystems, including 49% fewer trails, 35% less trampled bare ground, and 227% more canopy cover. Cougar predation on introduced donkeys rewires an ancient food web, with diverse implications for modern ecosystems.