Print PageThe relation between predators and their prey has motivated a long history of study, from basic ecological models to evolutionary theories of long-term persistence. Empirical evidence of how body size allometries are related to trophic interactions, however, have not kept pace with theoretical advances. Data is presented that relates total predator to prey biomass density (kg/km2) for whole ecosystems in east and southern Africa. Many of these ecosystems are represented over multiple decades and seasons, and span about two orders of magnitude in biomass density from the dry Kalahari Desert to the lush Ngorongoro Crater (n = 46 ecosystem time-periods spread over 20 regions and comprising over 900 animal population census estimates).
Results/Conclusions
Predators are shown to scale to their prey with a near three quarter power law when enumerated in terms of total trophic biomass density, recalling many metabolic allometries. This relation is considerably stronger than any single population against any other in terms of biomass or abundance, implying that the whole ecosystem is constrained in ways that individual populations are not. The fact that the power of the relation is so significantly less than one appears to counter previous empirical findings and suggests that population regulating mechanisms appear to operate to sustain ecosystem-level properties, especially in more productive environments. With few assumptions, this relation can be shown to resemble the production to body size allometry, and if it can be verified in other ecosystems, it raises the question of how energetic constraints may be acting over different levels of biological organisation, from the individual to the whole ecosystem.
