Intestinal parasite infection exposes grouse to canine predators

Background Sublethal parasite infections may cause mortality indirectly by exposing the host to predation. The best known example of this among birds is red grouse in which caecal nematode infection causes increased risk of predation and can even affect population dynamics [1]. Intestinal helminth parasites are common in forest grouse, capercaillie Tetrao urogallus, black grouse Tetrao tetrix and hazel grouse Bonasa bonasia [2], 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 grouse hunted with a trained dog to that of grouse hunted without a dog. Hunting with a dog can be regarded as close simulation of natural predation because the dog presumably locates the prey by the same cues as wild canine predators.