BILLINGS, Mont. -- U.S. wildlife officials rejected petitions Thursday to protect Yellowstone National Park's storied bison herds but pledged to consider more help for two other species — a tiny, endangered squirrel in Arizona and bees that pollinate rare desert flowers in Nevada.
Wildlife advocates have campaigned for decades to halt the routine slaughter of bison migrating out of Yellowstone to reach their winter grazing grounds in Montana.
The burly animals, also known as buffalo, once numbered in the tens of millions before overhunting reduced them to just a few small herds.
The U.S. Fish and Wildlife Service rebuffed calls for special protections for Yellowstone bison in 2015 but was forced to reconsider under a U.S. District Court order issued last year.
Wildlife service spokeswoman Jennifer Strickland said there's no scientific information showing bison should be treated as a threatened species.
The park's slaughter program, along with hunting of the animals in Montana, is meant to prevent the spread of the disease brucellosis, which can cause bison, elk and cattle to abort their young.
"The overall numbers of bison are stable despite culling and the presence of brucellosis," Strickland said, adding that the park has as many bison as it can hold.
Darrell Geist with the Buffalo Field Campaign said the government's decision ignored the fact that one of the park's two major bison herds has been in steep decline, which Geist said could have implications for the herd's genetic health.
The so-called central herd declined from more than 3,500 animals in 2006 to 847 in 2017, according to park biologists. Yellowstone's northern herd grew from about 1,500 bison to almost 4,000 over that time period.
Regarding the Mount Graham red squirrel of eastern Arizona, officials agreed to consider whether more habitat protections are needed. Weighing a mere 8 ounces, the squirrels are found solely in the Pinaleno Mountains.
Fires, roads and developments including a University of Arizona telescope complex have impacted the squirrel's range. An estimated 75 remain in the wild.
Wildlife advocates contend the squirrels' only hope is the removal of the telescopes, some nearby recreational cabins and a bible camp in the area.
"It's an incredibly precarious situation," said Robin Silver of the Center for Biological Diversity, which sued government officials last year to force a decision on the group's 2017 petition for more habitat protections. "If you want to try to have these animals survive you have to remove those structures."
In Nevada, officials said the Mojave poppy bee faces potential threats from grazing, gypsum mining, recreation and competition from honeybees. Its survival is closely linked to two rare desert poppy flowers in the Mojave Desert.
Federal law allows citizens to petition for plants and animals to get protections under the Endangered Species Act.
The positive finding on the petitions for the poppy bee and red squirrel means officials will conduct more intensive reviews before issuing final decisions.