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

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary1. 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. 2. 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. Nests of treated and untreated females were subsequently located either by research workers flushing the incubating female or by dogs trained to locate birds by scent.The dogs found significantly fewer of the treated than control birds, suggesting that female grouse with large parasite burdens emit more scent and are more vulnerable to mammalian predation. 4. A modified mathematical model of the grouse-nematode system is described which incorporates the effects of both random and selective predation of heavily parasitized grouse. An analysis of the model illustrates the importance of interactions between grouse, parasites and predators in determining the relative densities of each. In particular, when predators selectively remove heavily parasitized individuals, then low levels of predation can lead to increases in the size of the host (or prey) population.

Non-visual crypsis: a review of the empirical evidence for camouflage to senses other than vision

“…These promising results very much warrant further investigation in a more realistic setting, if possible with natural predators. Hudson et al (1992) provide good evidence for a parasite-induced increase in the scent produced by grouse in such a way as to increase vulnerability to mammalian predators (the ultimate hosts of the parasites concerned). Grouse treated with an anthelmintic drug were less easily found by dogs trained to hunt by scent than control birds.…”

The sociality–health–fitness nexus: synthesis, conclusions and future directions

“…[30,31]), and ectoparasites are known to transmit infectious agents, such as the Lyme disease spirochete [32], which may negatively impact fitness. Why did Raveh et al [8] fail to find support for their predictions in these ground squirrels?…”

Pathogen Exclusion from Eco‐Epidemiological Systems

“…There are many examples where this happens: the European tapeworm Echinococcus multilocularis is established in both wolf and moose on Isle Royale (Hadeler and Freedman 1989). There is heavy mortality of migrating pelicans feeding on infected fish in the highly toxic Salton Sea (Kaiser 1999), and predation affects the incidence of infection (Trichostrongylus tenuis) in red grouse attacked by foxes (Hudson et al 1992). The complexity here arises from the interaction between infection and predation, where the predator may or may not be host to the pathogen.…”