Colonisation strategy in Beaver and Coypu

 Released in 1974, the beaver Castor fiber is colonising the river Loire. The first five years after re-introduction, the colonisation rate was high and showed a rapid depletion during the following 20 years

After 5 years, the number of beaver colonies per km remained stable throughout the years but beavers exhibited an irregular colonization pattern. Beavers showed a scattered distribution occupying only 25% of the river system. Habitat selection emphasised the ecological importance of the deciduous riparian forest.

 The expansion of feral populations demonstrated the coypu Myocastor coypus adaptability to new environments. This ability is generally attributed to the flexibility of the reproductive biology based on polygynous mating system and engendering numerous litters throughout the year. In Grand Lieu, coypu population dynamics exhibited very original characteristics:

• A balanced sex ratio

• a low mean density but seasonally contrasted

• a belated reproduction peak reducing the generation renewal

• an exogenous contribution from peripheral populations

 
Radiotracked coypu Myocastor coypus in Grand-Lieu Lake 

FUSTEC J., CORMIER J.P. &LODÉ T. 2003. Beaver lodge location on the upstream Loire River C.R. Biologies, 326: 192-199, anciennement C. R. Académie des Sciences Vie/Life Sciences.

FUSTEC J, LODÉ T, LE JACQUES D & CORMIER JP. 2001. Colonisation, riparian habitat selection and home range size in a reintroduced population of beavers Castor fiber in the Loire. Freshwater Biology 46: 1361-1371

LODÉ T. 1999 - Des intrus involontaire: le ragondin et le rat musqué. Le Courrier de la Nature 175 : Spécial Grand-Lieu. 24-25.

LODÉ T. & MARION L. 1997 Biologie des populations de Myocastor coypu sur la Réserve Naturelle de Grand-Lieu. Rapport CNRS. 68p.