Ref ID : 957
G.F. Gause, N.P. Smaragdova, and A.A. Witt; Further studies of interaction between predators and prey. J.Animal Ecology 5(1):1-18, 1936
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In this paper an account is given of our recent experimental and mathematical investigations on the nature of interaction between predators and prey, which have been carried out along three different lines. Firstly, some new experimental data are presented dealing with a population of two species of mites, one of which, Cheyletus eruditus, feeds upon the other, Aleuroflyphus agilis. In these experiments an analysis is made of the effect of properties of the environment upon interaction by keeping the mites in various nutritive substances (wheat flour, millet, and semoletta). It is found that the predator is much more efficient in the open millet of semoletta environment, where the prey is more available than in the wheat flour. Concerning the true nature of interaction, it is concluded that under the environmental conditions studied in this work the interaction between the two species of mites forms a relaxation interaction, so that periodic oscillations are prevented after one "cycle". But when an immigration is allowed such oscillations immediately arise. Some data are also given on age distribution and its variation in the course of the interaction. Secondly, the classical case of relaxation interaction presented by two Infusoria, Didinium nasutum as predator and Paramecium caudatum as prey, is studied in detail from a mathematical viewpoint. An adequate differential equation of interaction between these two species based on experimentally observed biological properties of this system is formulated and leads to relaxation of interaction between them, which has been actually observed in our previous experimental investigations. The third line of study is devoted to interaction between Paramecium bursaria and yeast cells, Saccharomyces exiguus. New experimental data are given showing, in accordance with previous observations, the possibility of continuous periodic fluctuations resulting from the very process of interaction between these two species. At the same time an impossibility of a stable combination between Paramecium and yeast cells is demonstrated and the curves of interaction are traced in detail. Independently of these fluctuations two biological peculiarities of the food chain under investigation are pointed out: the existence of a threshold value in the specific consumption of prey by predators (which is due to biological conditions of consumption), and the probable "non-rigidity" of their dependence. These two properties, formulated in a differential equation of interaction, lead to periodic fluctuations in numbers corresponding with those observed in the experiment. It is therefore probable that the basic features of interaction are in this way properly demonstrated.