Population ecology is the study of the structure and dynamics of populations. The term population has many definitions. We will use it here to mean a group of individuals of the same species inhabiting the same area (Mackenzie et al. 1998). Population characteristics are based on the individual characteristics of the individuals within the population. We describe populations in terms of their size, age, and structure. Along with the populations physical attributes, we also must consider the factors which affect the population such as mortality from competition and predation (Mackenzie et al. 1998). We call the study of changes in populations through time population dynamics.