A further interesting characteristic of the second cluster is that cluster members, controlling for life history stage and size, showed significantly better body condition and greater macroparasite infection than non-cluster individuals from the same time interval. This indicates that healthier individuals with more macroparasites might either be more susceptible to any putative infection or more resilient to the effects of infection. Increased susceptibility could arise because individuals in better condition eat more and range farther, exposing themselves to greater infection risks from macroparasites and microbial infections. Macroparasites might also contribute to susceptibility due to their anti-inflammatory activities [18] . Increased resilience could occur because animals in better starting condition might be more likely to survive infection, thus raising their representation in infected classes by differential mortality. The immunoregulatory influence of macroparasites might also be important in this context: dampening potentially lethal immunopathogenic inflammatory responses. A further possibility is that individual mice respond to infection by adjusting life history traits in a way that produces an overcompensatory response in body condition. For example, A. sylvaticus infected with cowpox virus in summer may show positive effects on survival due to a diversion of resources from reproduction [3] .