The Role of Nutrition and Carrying Capacity in Models of Small Rodent Population Dynamics

Abstract

The asymptote of the logistic growth equation defines carrying capacity as the equilibrium density at which a population's intrinsic rate of increase is counterbalanced by the negative effects of crowding. Although the mechanism that produces this crowding effect need not be explicitly stated, most ecologists assume that the ultimate cause is a shortage of resources, usually food. Thus nutrition and carrying capacity are inextricably linked, and it seems appropriate to consider them together in a review of their treatment by modellers. There is no consensus as to the importance of resource availability as a factor limiting the density of natural populations. Other important environmental factors, such as weather, predators and disease, may keep populations well below limitations set by food supply. But that neither vitiates the concept of resource limitation nor reduces its usefulness for modelling. We need to know how environmental factors influence population densities when acting in concert, and no one factor is likely to dominate the others completely. The combined effects of factors on populations are not likely to be modelled appropriately if the effects of individual factors are not correctly expressed, so again each major factor is worthy of careful consideration. Both the quantity and quality of food influence the carrying capacity of a habitat, which suggests that nutritional measures can be used as indicators of habitat