Do Parasites make Prey Vulnerable to Predation? Red Grouse and Parasites

Abstract

An extensive post-mortem survey of grouse revealed that birds killed by predators in spring and summer had significantly greater burdens of the caecal nematode Trichostrongylus tenuis than grouse shot during the autumn. Furthermore, grouse that appeared to have died through the effects of parasites carried greater worm burdens than grouse killed by predators. The proportion of grouse with high levels of parasite infection increased with the intensity of predator control as measured indirectly through keeper density. These two empirical observations suggest that predators selectively prey on heavily infected grouse. The interactions between parasites and predators were examined experimentally by reducing the worm burdens of female grouse with an oral anthelmintic