Bison-Rewilding-Plan-2014

2. The founder groupA good social and organisational structure isimportant prior to the release into the wild forsecuring protection against predators and establishingdominance and position in the herd. Forthis reason young animals should always beaccompanied by adult animals in releases. Thisprovides social stability to the herd, gives theyoung animals survival skills and helps protectthem from predators. In turn this will help reducestress levels, increase reproductive success andenable survival behaviours to be passed on. Socialinteractions also affect foraging behaviour, whichmay influence how bison use landscapes.It is also important that the founder populationrepresents the maximum genetic variabilitypossible. The individuals that form the foundergroup will therefore come from different institutions.Following Frankham et al. (1998) a minimumof 50 animals is needed to avoid inbreedingdepression and > 500 are required to retain evolutionarypotential and ensure overall genetic variability.Decreased genetic variability resultingfrom inbreeding depression can lead to negativeconsequences such as lowered fecundity, reducedgrowth, lower breeding success and greatersusceptibility to disease. Ideally 50 unrelatedbison should be used to form the founding group.However in the case of the bison it is unlikely thiscan be achieved due to the history of the speciesand also for practical reasons within an acceptablefinancial budget. For practical reasons an effectivealternative is to introduce several young unrelatedbulls instead of one dominant adult male. If thefounder group of animals has to be small forpractical reasons (e.g. due to limited size of theacclimatisation zone /semi-wild reserve area) andthere is only one dominant bull, this individualcan be replaced every generation to preventinbreeding.Rewilding Europe wants to start with an initialfounder group of 10–20 animals, followed withyearly herd supplementations, with a minimumof 10 animals on average per year over a 10 yearperiod. Rewilding Europe will primarily makeSTAFFAN WIDSTRAND / REWILDING EUROPE51