Natural mortality among bison is low and the space they demand vast ; five bison per 1,000 hectares of land is deemed the optimal density . European bison have been successfully reintroduced to Poland . Comment: Around 1,200 animals are closely monitored by conservation groups . Controlling population is now an issue with hunting a controversial proposal .
European bison have been successfully reintroduced to Poland . Comment: Around 1,200 animals are closely monitored by conservation groups . Controlling population is now an issue with hunting a controversial proposal .