title: Social living mitigates the costs of a chronic illness in a cooperative carnivore.
abstract: Infection risk is assumed to increase with social group size, and thus be a cost of group living. We assess infection risk and costs with respect to group size using data from an epidemic of sarcoptic mange (Sarcoptes scabiei) among grey wolves (Canis lupus). We demonstrate that group size does not predict infection risk and that individual costs of infection, in terms of reduced survival, can be entirely offset by having sufficient numbers of pack-mates. Infected individuals experience increased mortality hazards with increasing proportions of infected pack-mates, but healthy individuals remain unaffected. The social support of group hunting and territory defence are two possible mechanisms mediating infection costs. This is likely a common phenomenon among other social species and chronic infections, but difficult to detect in systems where infection status cannot be measured continuously over time.
authors.affiliation: Department of Biology, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, USA.
authors.forename: E S
authors.initials: ES
authors.lastname: Almberg
authors.affiliation: US Geological Survey, Northern Rocky Mountain Science Center, Bozeman, MT, USA.
authors.forename: P C
authors.initials: PC
authors.lastname: Cross
authors.affiliation: Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA.|Santa Fe Institute, Santa Fe, NM, USA.
authors.forename: A P
authors.initials: AP
authors.lastname: Dobson
authors.affiliation: Yellowstone Wolf Project, Yellowstone National Park, WY, USA.
authors.forename: D W
authors.initials: DW
authors.lastname: Smith
authors.affiliation: Yellowstone Wolf Project, Yellowstone National Park, WY, USA.|College of Forestry and Conservation, University of Montana, Missoula, MT, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Metz
authors.affiliation: Yellowstone Wolf Project, Yellowstone National Park, WY, USA.
authors.forename: D R
authors.initials: DR
authors.lastname: Stahler
authors.affiliation: Department of Biology, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA, USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Hudson
mesh_terms: D000818:Animals; D001070:Appetitive Behavior; D002908:Chronic Disease / Q000453:epidemiology; D003299:Cooperative Behavior; D011156:Population Density; D016016:Proportional Hazards Models; D012307:Risk Factors; D012520:Sarcoptes scabiei; D012532:Scabies / Q000453:epidemiology* / Q000635:transmission*; D012919:Social Behavior; D013731:Territoriality; D019596:Wolves / Q000469:parasitology*; D014959:Wyoming
keywords: Grey wolf; infection costs; infection risk; parasite; sarcoptic mange; social immunity; sociality