A judge has ruled that U.S. wildlife managers erred in denying Endangered Species Act protection to bison at Yellowstone National Park and must reconsider extending such safeguards to America's largest pure-bred herd of wild buffalo.

The decision was welcomed on Thursday by wildlife advocates who petitioned the Obama administration in 2014 to protect bison in and around Yellowstone, where animals wandering outside park boundaries are culled for slaughter by the hundreds each year.

The seasonal culling is supported by ranchers in the region, particularly in Montana, concerned about exposure of livestock to disease, competition for grass and property damage from straying bison.