Chronic wasting disease in the Greater Yellowstone Ecosystem: predicting the effects of predators on creating healthier herds

Dr. Ellen Brandell

Postdoctoral Researcher, University of Wisconsin-Madison

Abstract

Predators may create healthier and larger prey populations by preying upon the sickest individuals. Previous work has not accounted for how pathogens and disease transmission may be concentrated in some age groups, which may be the same or different age groups as those that are normally preferred by predators. Here we explore this general issue using a specific case study of chronic wasting disease (CWD), using a simulation model based on empirical data collected from Yellowstone National Park. We found that, under moderate to high predation pressure from cougars and wolves, predators decreased CWD outbreak size up to 5-fold and delayed the accumulation of the symptomatic deer and elk populations by decades. Predators often prefer juvenile and senescent prey, whereas chronic pathogens tend to be more common in older age categories; thus, predators that prefer infected prey over healthy juveniles will have a stronger cleansing effect.