(Francisco Kjolseth | The Salt Lake Tribune) Riders on horseback herd bison during the 33rd annual roundup, Saturday, Oct. 26, 2019, on Antelope Island. Every year Utah wildlife and parks officials move the animals from across the island so they can be weighed, tagged and given health screenings. Evidence is mounting that wild North American bison are gradually shedding their genetic diversity across many of the isolated herds overseen by the U.S. government, weakening future resilience against disease and climate events in the shadow of human encroachment.