Do keystone prey sustain endangered mountain red foxes?
Sierra Nevada red fox (left) and coyote (right) carrying a white-tailed jackrabbit, a key subalpine prey that shapes competitive dynamics.
High in the peaks of its namesake range, fewer than 50 Sierra Nevada red foxes remain. This scarcity makes this high-elevation subspecies of red fox both endangered and difficult to study. For managers, limited information means uncertainty about how different actions might help or hinder its recovery.
To better understand the conditions that support long-term persistence, scientists from the University of California, Davis and the USDA Forest Service analyzed DNA from scats to determine what these foxes and nearby carnivores were eating. While coyotes and red foxes ate similar foods, foxes relied more heavily on "snow-adapted" prey, such as snowshoe hares, white-tailed jackrabbits, and American pika. The dietary differences between coyotes and foxes were most pronounced during winters with deep snow: coyotes ate fewer jackrabbits, while red fox consumption remained high. The different patterns suggest that deep snow provides Sierra Nevada red foxes with a hunting advantage over their larger-bodied competitors.
Whitebark pine also appeared more frequently in red fox diets during winter. This seasonal spike in consumption suggests that caches of whitebark pine nuts stored by other animals offer a critical fallback source of calories that help foxes survive harsh alpine winters. Declining whitebark pine populations may compromise the ability of Sierra Nevada red foxes to cope with the resource-scarce winter bottleneck.
These findings show that protecting the Sierra Nevada red fox takes more than focusing on the species itself—recovery depends on maintaining the health of the entire alpine ecosystem. Conserving key prey, plants, and the snowy habitats that support them helps to preserve the ecological separation, or “niche partitioning,” that lets specialist alpine carnivores, such as the iconic Sierra Nevada red fox, coexist alongside its more widespread generalist competitors.