Aggressive gray wolf hunting took a toll in much of the Northern Rockies last year as the predator's population saw its most significant decline since being reintroduced in the region.
Numbers released by state wildlife agencies show Wyoming's wolf population down 16 percent from 2011, Montana's down 4 percent and Idaho's down 8 percent.
That was partially offset by population gains in eastern portions of Washington and Oregon.
Federal wildlife officials are expected weigh in Friday on whether the population remains sustainable two years after wolves lost their endangered species protections in most of the region.
Overall, biologists tallied a minimum of 1,674 wolves across the five states at the end of 2012, a 6 percent decline.
The government's original recovery goal was at least 300 wolves in the region.