The Effect of European Bison (Bison bonasus) Translocations on the Persistence and Genetic Diversity of Ex Situ Herds—A Modelling Study

Abstract

The conservation of the genetic diversity of the European bison population is carried out mainly in ex situ herds, constituting a functional metapopulation. The breeders have to balance between the available capacity of the reserves and the need to enrich the free and semi-free herds with appropriate individuals. If there are limitations (e.g., financial) in the transfer of individuals, breeders report a problem of surplus individuals. The aim of this study was to estimate the migration parameters in the wisent metapopulation ex situ to maintain genetic diversity in hypothetical herds. The analysis was a two-step process. The first part of this study was carried out between the years 1998 and 2017, based on information from the European Bison Pedigree Book about eight selected herds. The average annual share of exported and imported individuals in the chosen metapopulation were calculated (8.81% (SD: 11.51) and 0.75% (SD: 2.15), respectively). The proportion of males to females among the exported animals was close to 1:1. The sex ratio of imported animals was close to 2:1 (M:F). The majority of transports were exports of animals (92.1%). The share of individuals exported from different age–sex groups was calculated. On this basis, in the second part of the study, the proportion of exported surplus individuals in the smallest hypothetical herd was established as 5.89% of the adult females, or 8.98% of adult males, or 32.70% of females aged 1–3 years. In order to maintain the genetic sustainability of hypothetical herds it is crucial to import individuals (M/F: 1/1; interval: 10 years). The results of this study will provide necessary information to determine the tools of wisent population management in the enclosure.