"We do not believe the bison population level is too high or that any scientific studies would substantiate that," Superintendent Dan Wenk says.
Wednesday's proposal affects conservation plans for grouse in Wyoming, Idaho, Nevada, Colorado, Utah, California and Oregon.
Investigators said they were unable to determine if anything illegal occurred because the agency leaders did not document their rationale for the reassignments.
Zinke has made reorganizing the Interior — which manages 780,000 square miles of public lands, mostly in the West — a signature mission since taking over the agency.
The changes follow complaints from a bipartisan group of Western state governors that the secretary did not consult them.
A year into his tenure, Secretary Ryan Zinke has emerged as the point person for the administration's goal of American "energy dominance."
The proposal would relocate many of the Interior Department's top decision-makers from Washington to still-undisclosed cities in the West.
Interior had previously announced it was delaying the Obama-era rule until January 2019, arguing that it was overly burdensome to industry.
Some Westerners have long argued federal land managers should be closer to the land they oversee.
Interior Secretary Ryan Zinke has started a major push to reorganize the agency and get thousands of employees out of Washington D.C.