Food Selection of the Field Vole Microtus agrestis

This is the application of a model on food selection in grazing microtine rodents. Net gain functions for any particular food value, the currency to be optimized, are constructed by evaluating the abundance, distribution, and cost of acquisition of different food items. In the specific application of the model, digestible energy content is used as the currency. The basic premise in the hypothesis is that microtines select their diet to ensure that the net energy gain per effort is maximized. The theory is used for evaluating the food selection of field voles Microtus agrestis (L.) in two localities in Scandinavia (northern Sweden and southern Finland). There is close agreement between predictions and observations. Alternative hypotheses (e.g. food selection for nutrients) are evaluated, but found less likely than the one discussed here. Nutritional consequences of food selection for energy-per-effort as well as consequences at the population level of organization are evaluated.