Major food pulses can shift the diets of wildlife over short periods, but little is known about the downstream consequences of foraging decisions on parasite loads. In the current study, we capitalized on our observations of the novel emergence of widespread hunting and carnivory of California voles (Microtus californicus) by marked individual California ground squirrels (Otospermophilus beecheyi) in June and July of 2024. Rodents can be definitive hosts, harboring adult tapeworms in their gut if they ingest tapeworm eggs or intermediate hosts (i.e., infected insects harboring tapeworm eggs). We predicted that sudden dietary shift towards eating other mammals may influence the prevalence of tapeworms in ground squirrels. As part of long-term study on California ground squirrels in the San Fransico Bay Area, we conducted fecal floats to quantify the prevalence of tapeworms in two study populations of ground squirrels before (2023), during (2024), and after (2025) the vole hunting year. Whereas tapeworms were prevalent in squirrel fecal samples before and after the vole boom, tapeworms were rarely present in vole-year samples. Our data is consistent with the notion that dietary shifts can radically influence the prevalence of parasites suggesting that ecological shifts can influence the health of animals.
