Experimental studies on predation: Dispersion factors and predator-prey oscillations

Abstract

Experimental studies on the role of dispersion in predator-prey relations was studied under controlled laboratory conditions using the phytophagous mite Eotetranychus sexmaculatus as prey, and the mite Typhlodromus occidentalis as predator. The results are a beginning toward answering some of the theoretical questions presented to population ecologists. The present data indicate that if an adequate environment is encompassed, the predator-prey relation is not necessarily self-annihilative, and that absolutely restrictive refuges are not essential. The results also support the view that more stable control of a population is likely to result in an environment of balanced heterogeneity than in one of simpler structure. In this study a predator-prey relation was maintained for three successive oscillation waves before overexploitation finally ended the relation in the most complex universe or ecosystem utilized. Some of the questions which may ultimately be answered by such studies include: Are such oscillations inherently of increasing amplitude? If so, are there commonly present forces which act to cancel this tendency? Does the presence of other significant species in addition to the two original coactors tend to stabilize or disturb the relation? What may be the effect of changes in the physical conditions upon the degree of stability or permanence of the relation? Can evidence be obtained regarding the concept that the prey, as well as the predator, may benefit from the relation? What is the order of influence on stability of such factors as shelter, food, disease, and natural enemies of other kinds?