ABSTRACT
This chapter presents a number of case studies that illustrate the different mechanisms through which infectious agents can influence wildlife populations and case studies from a variety of different species and systems, using Rangifer examples where available. Infectious agents are generally divided into two broad classes: ‘microparasites’ and ‘macroparasites’. Augmentation of infectious agents in individuals or populations permits direct measurement of the impact of the agents. To influence population dynamics, infectious agents must ultimately alter the birth or death rates of their hosts. An experimental study has also demonstrated a link between parasite infection and a reduction in Rangifer body condition. Some infectious agents, particularly viruses and bacteria, can cause direct mortality of their hosts, whereas others may be less virulent and only cause mortality through interaction with other biotic and abiotic elements of the ecosystem. Infectious agents, their hosts and predators interact with many different ecological communities.
