Grand Canyon National Park has decided not to extend a pilot project this fall that used volunteers to kill bison as a way to downsize the herd.
New surveys show the herd roaming the far reaches of northern Arizona is closer to the goal of about 200.
Park officials also say the gunfire and presence of humans wasn't enough to push the bison outside the park boundaries where they can be hunted.
The park approved a plan in 2017 to quickly reduce the herd from about 600 to 200 animals. It's now working with other agencies to develop a long-term plan to manage the animals.
In recent years, the herd has damaged the park’s water, vegetation, soils and archaeological and cultural sites.
Animals that were live captured were transferred to the Santee Sioux Nation of Nebraska as well as the Cherokee Nation in Oklahoma.
The Park Service began the Bison Herd Reduction plan in 2017 with the goal of reducing the numbers and to disperse the herd.