Parasitized grouse are more vulnerable to predation as revealed by a dog-assisted hunting study

Sublethal parasite infections may cause mortality indirectly by exposing the host to predation. Intestinal helminth parasites are common in forest grouse, the capercaillie Tetrao urogallus, the black grouse Tetrao tetrix and the hazel grouse Bonasa bonasia, and these grouse are valuable prey for several species of predators. We evaluated the hypothesis that parasite infection makes the host more vulnerable to predation by comparing the intestinal parasite infection status of arouse hunted with a trained dog to that of grouse hunted without a dog. Cestode infections were more common in grouse hunted with a dog supporting the hypothesis. Cestodes were mostly parasites of juvenile grouse but even among juveniles only, cestodes were more prevalent in dog-assisted hunting bag. The results suggest that mammalian predators could prey more selectively on parasitized individuals and that intestinal parasites may contribute to the high mortality of juvenile grouse through increased predation.