When Theory Meets Practice: Balancing Genetic Diversity and Behaviour When Choosing Founders for a Recently Reintroduced Bison (Bison bison) Herd in Banff National Park, Canada

Abstract

The tragic decline of plains bison (Bison bison bison) in North America is well known. By the turn of the 20th century, plains bison, once numbering in the tens of millions, were extirpated from the wild in Canada. Banff National Park, AB, Canada, is within the original range of bison in North America, and still contains suitable habitat for the species. In 2017, we used measures of genetic diversity, as well as age and reproductive status, to select 16 plains bison for reintroduction to an unoccupied corner of their former historic range in Banff National Park. However, five of the preferred founders from this genetically diverse group needed to be substituted for less ideal candidates when aggressive behavior was observed, which could have compromised animal welfare during translocation. The level of genetic diversity in the founding population was therefore lower than if all proposed founders had been used, although the difference was not substantial. As expected, adults in this small, reintroduced herd had lower observed heterozygosity and number of alleles than the larger source herd, but expected heterozygosity was higher, likely a result of preferentially choosing individuals with rare alleles. Another substantial contribution to genetic diversity was in unborn fetuses: sired by males that were not translocated, the calves born a few months later provided a boost to the genetic diversity of this small founder herd. Where opportunities allow, the inclusion of pregnant females can significantly increase the genetic diversity of small founder populations. When compared to other founded herds of bison, the techniques described here have ensured that the newly established Banff NP herd is one of the most diverse bison herds in Canada, despite its relatively small number of founders.