Living in a social group has many benefits for wildlife but is often assumed to come at the cost of increased disease risk. However, new research on the effects of mange on gray wolves in Yellowstone National Park reveals that infection risk does not appear to increase with the size of the pack. Also, while solitary wolves with mange had a 5-times higher death rate compared with solitary healthy wolves, infected wolves surrounded by five or more healthy pack-mates survived just as well as uninfected wolves. In addition, while the mortality rates of infected wolves increased as more wolves in their pack were also infected, both uninfected and infected wolves still accrued a net survival benefit from living in a social group.
"We hypothesize that pack-mates are able to offset the effects of mange--and perhaps other infections--by assisting with food acquisition and territory defense," explained Dr. Emily Almberg, lead author of the Ecology Letters study. "Our work provides the first evidence in a wild mammal of the benefits of group living for mitigating the impacts of a chronic disease and is one of the first non-human studies to quantify the costs of infected individuals to their group-mates."