Metabolic scaling from individuals to societies

The flux of energy and materials constrains all organisms. Allometric relationships between rates of energy consumption and other biological rates are manifest at many levels of biological organization. Here I examine relationships between social organization, energy consumption and reproductive rates. First, I present a model relating fertility rates to per capita energy consumption rates in contemporary human nations. Fertility declines as per capita energy consumption increases with a scaling exponent of -1/3 as predicted by allometric theory. Second, I examine the tradeoffs that occur between life history characteristics as mammals allocate energy to reproduction. The analysis shows that although reproductive effort is independent of adult mass, larger mammals have lower reproductive rates because they spend more time providing energy to grow each offspring. Third, I present the Allometric Network Travel and Search (ANTS) model of optimal colony foraging behavior as a function of colony size. Field observations of three Pogonomyrmex species show that large and small colonies employ different foraging strategies, each designed to minimize foraging time such that foraging times of individual ants are very similar across a 30-fold difference in colony size. As a result, metabolic intake rates of colonies scale isometrically with the number of foragers in the colony. Finally, I show that because they integrate all parts of an individual or society, metabolic networks have allometric scaling of delivery capacity with network size. This common scaling behavior may lead to common patterns in energy acquisition and allocation in individuals and societies.