Etude de l’impact du castor sur son écosystème et dynamique de sa population dans le bois de Lauzelle

Details

Supervisors

Wesselingh, Renate A. ; Thyrion, Thibaut

Faculty

Faculté des sciences

Degree label

Master [120] en biologie des organismes et écologie, à finalité approfondie

Abstract

enIn the 2000s, the world's second largest rodent re-colonised our regions. Following legal and illegal reintroduction programmes, the first wild beaver was spotted in Belgium after an absence of 140 years. This animal, present in our wetlands, is a species recognised for its role as an engineer of riparian ecosystems. Through its various activities, particularly construction, it helps to change the appearance of the landscapes in which it is found. The aim of this thesis is to gain a better understanding of the beaver's impact on the ecosystems of the bois de Lauzelle and to analyse its population dynamics. The first part of the study focuses on the impact that the beaver's presence could have on 3 environmental variables: the composition of plant communities, ground luminosity and the number of standing dead trees. These 3 variables are analysed according to the presence factor, which is divided into three levels: absent for more than 5 years, absent for more than 6 months, present. All the variables were measured in 8 different study squares defined in collaboration with the forest warden in charge of the wood. Although the statistical tests carried out on the measurements of the plant community factor proved to be non-significant, the p-value observed is only slightly above the threshold and confirms a trend: the presence of the animal has an effect on the plant communities in the study plots. The measurements taken and their statistical analysis do not allow us to conclude that the presence of the beaver has an effect on ground luminosity in the 8 squares studied. A change in the measurement methodology could undoubtedly produce results more in line with the literature. On the other hand, the number of standing dead trees appears to be correlated with the presence of the rodent. A greater number of standing dead trees was observed in recently abandoned areas. The second part of this thesis studied the dynamics of the beaver population and, more specifically, the number of individuals and their movements within the bois de Lauzelle. The use of photographic traps coupled with several nocturnal stalks enabled the animals to be observed and a preliminary estimate to be made of the number of individuals in the ood and a better understanding of their movements. Analysis of the changes in the size of the various dams found in the wood confirmed that the population had moved to a new area, highlighting the way in which the species manages its environmental resources. Hair traps were used to collect DNA samples from the various beavers present for genetic analysis. The results provided a better estimate of the number of individuals and their relationship. In conclusion, this work could help to set up future management plans for the Bois de Lauzelle by highlighting some of the ecological effects of the presence of beavers and by clarifying the size and dynamics of their population.