Modelling of competitive interactions between native Eurasian (Castor fiber) and alien North American (Castor сanadensis) beavers based on long-term monitoring data (1934–2015)

Abstract

Our goal is to assess consequences of the introduction of alien North American (Castor сanadensis (Cc)) beaver into the Nature Reserves inhabited by Eurasian beaver (Castor fiber (Cf)) in European Russia using a mathematical model. For this reason, we have developed a two-species model of population dynamics. Long-term (1934–2015) monitoring data on Cf population dynamics in six Nature Reserves are used in computer modelling of competitive interactions between native Cf and alien Cc. The Reserves are located in the European part of Russia in the north, south, and central part of Cf range. We have simulated the dynamics of both species populations after the introduction of Cc into the habitats occupied by Cf. The model demonstrates that Cf is displaced by Cc in all the Reserves after the introduction of 2 – 24 individuals of Cc. However, the duration of exclusion of one species by the other varies as a function of ecological conditions, initial number of individuals, and fecundities. Our model shows that, in case of introduction of 12 Cc beavers, the size of Cf population starts to decrease after 31–146 years as a result of competition. We study the conditions providing the coexistence of both species and find that Cc population dynamics after Cf exclusion can be described by four patterns: irruptive (Lapland Reserve), single-stage (Prioksko-Terrasny Reserve), multi-stage (Darwin, Central-Forest, and Khoper Reserves) and logistic population growth (Oka Reserve). Species biology in terms of the fecundity, family size, rate of individual development until sexual maturity, life-span, and the age structure of populations are compared between species to detect the mechanisms providing the competitive advantage of Cc over Cf.