Examination of the interaction between age-specific predation and chronic disease in the Greater Yellowstone Ecosystem

The patterns of parasite infections in wildlife hosts often have an age component. For example, the prevalence of chronic infections tends to skew towards older individuals that have had a longer amount of time to be exposed (e.g. Heisey et al., 2006). Conversely, intestinal parasite infection prevalence is skewed towards younger individuals (e.g. Cattadori et al., 2005). Predators can improve the health of prey populations by selectively removing infectious individuals (Packer et al., 2003), and their foraging behaviour and impact on prey abundance often vary by prey species, age, sex and condition (e.g. Gervasi et al., 2012; Hoy et al., 2021). Little is known, however, about how age-specific variation in parasite prevalence within prey populations alters the cleansing effect of predators that prefer certain age groups. While both age-specific infection and predation are well-studied, their intersection has not been previously explored and is likely very important for disease dynamics. We hypothesize that the predator cleansing effect will be more efficient in systems where the disease and predation are occurring in the same prey age groups. We test this hypothesis using a mathematical model based on predation and age structure data from cougars Puma concolor, wolves Canis lupus, elk Cervus canadensis and mule deer Odocoileus hemionus in Yellowstone National Park.