The role of parasites in influencing the trophic dynamics of hosts is becoming increasingly recognized in the ecological literature. Echinococcus granulosus is a tapeworm that relies on the predator-prey relationship between the definitive host (wolf, Canis lupus) and the intermediate host, (moose, Alces alces) to complete its life cycle. Heavy infection by E. granulosus may predispose moose to increased risk of predation by wolves. Theory predicts that parasite-induced vulnerability to predation will reduce the degree of aggregation of parasites in a host population. We tested for different levels of aggregation of E. granulosus in moose in areas of low, moderate, and high levels of wolf predation using Green’s coefficient of dispersion. Parasite aggregation was lower in an area with high predation rate, thus we hypothesize that heavy infection by E. granulosus predisposes moose to predation by wolves. This increase in predation rate due to parasite infection may influence the role of wolves in regulating moose populations. We discuss alternative explanations for the negative correlation between predation rate and parasite aggregation.
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This manuscript was improved by comments from C. Osenberg, K. Lafferty, S. Ferguson, D. Gummer, T. Armstrong and B. Patterson and an anonymous reviewer. We are grateful to A. Plante for technical support. Financial support for the original study was provided by the Canadian National Sportmen’s Shows, the Natural Sciences and Engineering Research Council of Canada (NSERC), and the Ministère du Loisir, de la Chasse et de la Pêche du Québec. Damien O. Joly was supported by the University of Saskatchewan and Natural Sciences and Engineering Research Council of Canada and subsequently the USGS-National Wildlife Health Center.
An erratum to this article can be found at http://dx.doi.org/10.1007/s00442-004-1802-1
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Joly, D.O., Messier, F. The distribution of Echinococcus granulosus in moose: evidence for parasite-induced vulnerability to predation by wolves?. Oecologia 140, 586–590 (2004). https://doi.org/10.1007/s00442-004-1633-0
- Alces alces
- Canis lupus
- Hydatid disease