While studies of laboratory animals allow aspects of immunity to be studied in controlled, repeatable environments, they may not reflect how wild animals, constrained by limited resources and at threat from a variety of infectious agents, respond to parasites and disease. We predicted that common shrews, which are short lived, store little energy as fat, and invest heavily in reproduction, would show limited responses to parasites, and their haemolymphatic tissues would deteriorate with age as expected survival decreased.