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In this paper we explore the cyclic interactions of prey-predator systems by examining the relationship between cycle lengths of both species and the strength of their interaction. As a probe of interaction strength, we use the degree of counter-clockwise rotation in phase plots with the prey on the x axis and the predator on the y axis. We compare the results from a 25-year time series from the Hudson's Bay Company data on American mink (Neovison vison (Schreber, 1777)) and muskrat (Ondatra zibethicus (L., 1766)) with results from three simulation models. We found that the strength of interaction (rotation range: -0.4 to 1.1 rad/year) was strongest when the two cycle lengths were similar and that it increased with the amplitude of the cycles (cycle range: 4-10 years). The time difference between prey and predator cycles that corresponded to the highest interaction strength was 2-3 years. Similar results were obtained with simulation models; the most complex Hanski model showing the overall best fit with observations. However, none of the models were able to reproduce long ranges of stable cycles by only changing one of their parameters at a time (ranges 2-4 years), whereas the observed range of stable cycles was 4-10 years. Resume : Nous examinons dans notre recherche les interactions cycliques des cycles proies-predateurs par 1'etude de la relation entre les longueurs des cycles des deux especes et l'intensite de leur interaction. Comme mesure de l'intensite de l'interaction, nous utilisons le degre de rotation dans le sens inverse des aiguilles d'une montre dans des diagrammes de phase sur lesquels les predateurs sont places en abscisse et les predateurs en ordonnee. Nous comparons les resultats d'une serie chronologique de 25 ans de donnees de la Compagnie de la baie d'Hudson sur les visons (Neovison vison (Schreber, 1777)) et les rats musques (Ondatra zibethicus (L., 1766)) avec les resultats de trois modeles de simulation. L'intensite de l'interaction (etendue de la rotation : -0,4 a 1,1 rad/annee) est la plus grande quand les deux longueurs de cycles sont semblables et elle augmente en fonction de 1'amplitude des cycles (etendue des cycles : 4-10 ans). Les differences temporelles entre les cycles de la proie et du predateur qui correspondent a l'intensite d'interaction la plus grande sont de 2 a 3 ans. Les modeles de simulation produisent des resultats semblables et le modele de Hanski le plus complexe presente le meilleur ajustement aux observations. Cependant, aucun des modeles n'est capable de reproduire des cycles stables a long terme par le changement successif des variables une seule a la fois (etendues 2-4 ans), alors que l'etendue observee des cycles stables est de 4 a 10 ans. [Traduit par la Redaction], Introduction Predator-prey systems may show regular cyclic behavior over time. We here hypothesize that cycle lengths and quantitative phase portrait characteristics of a predator-prey system can be used to predict [...]

Norwegian researchers examined the resource use, environmental effects, and emissions of eight paper mills in Norway. The study was conducted to evaluate the criteria in situating industrial plants that would do the least damage to the environment.