BILLINGS — Aggressive gray wolf hunting and trapping took a toll in much of the Northern Rockies last year as the predator’s population saw its most significant decline since being reintroduced to the region two decades ago.

Yet state and federal wildlife officials said Friday that the population remains healthy overall, despite worries among some wildlife advocates over high harvest rates. Its range is even expanding in some areas as packs take hold in new portions of eastern Washington state and Oregon.

Overall, biologists tallied a minimum of 1,674 wolves in 321 packs across the six-state Northern Rockies region at the end of 2012. That marks a 7 percent decline.

“We expected the states to bring the population down and that’s what’s been happening,” said Mike Jimenez, wolf recovery coordinator for the U.S. Fish and Wildlife Service. “They are bringing it down gradually.”

Wolf management was turned over to the states when the animals lost their federal protections over the last two years. Hunters and trappers legally killed a combined 570 wolves in Montana, Idaho and Wyoming last year.

State officials in the three states have been adamant about their desire to have fewer wolves on the landscape. The U.S. Fish and Wildlife Service will continue to monitor the species at least until 2016 to ensure they aren’t again wiped out as happened in the early 20th century.

The year-end numbers show Wyoming’s wolf population down 16 percent from 2011, to 277 animals. Montana’s numbers fell 4 percent to 625 and Idaho’s dropped 11 percent to 683.

That was partially offset by population gains in eastern portions of Washington and Oregon, where wolf numbers have been climbing rapidly over the last few years but still remain low compared to other parts of the region. 

Oregon now has 46 wolves in the eastern third of the state and Washington 43. Combined, that’s almost double the 2011 numbers.

The government’s original recovery goal, set in the 1990s, was at least 300 wolves across the region. Despite last year’s decline, the latest figures show the population remains at more than five times that level.

Parts of northern Utah also fall with in the Northern Rockies wolf recovery area, but the state has no wolves.

In Wyoming, wildlife officials this week said the state will halve its quota for the fall hunting season, to 26 animals. 

The proposal will be up for public review this spring. It applies only to the state’s trophy game areas for wolves in the northwest corner of the state around Yellowstone and Grand Teton national parks. Elsewhere in the state, wolves are designated as predatory animals that can be shot on sight.

If the population drops below 150 wolves or 15 breeding pairs in the state for three years in a row, the U.S. Fish and Wildlife Service has said it would step in to see if the animals need federal protections restored.

Wyoming Game and Fish spokesman Eric Keszler said the quota reduction is meant to keep that from happening. “While we still want to reduce the number slightly, we want to be conservative in our approach,” he said.

By contrast, in Montana and Idaho, wildlife officials have loosened restrictions on their wolf harvests and pledge to continue driving down wolf numbers to reduce attacks on livestock and big game herds.

Notwithstanding protests from wildlife advocates over the increasingly aggressive tactics hunters can use — including higher bag limits, longer seasons and the use of electronic calls — officials from both states contend they have enough wolves to ensure the species won’t be returned to the endangered list.

Wolf attacks on livestock were up last year, primarily due to large numbers of sheep being killed in a limited number of instances. Confirmed wolf depredations for 2012 included 194 cattle, 470 sheep, and six dogs.

In response to those attacks, wildlife agents and ranchers killed 229 wolves. That figure was up almost 30 percent from the prior year.

Wolves were exterminated across the Lower 48 states last century except in the Great Lakes region.

The Northern Rockies population has grown from 66 animals reintroduced to Yellowstone National Park and central Idaho in 1995 and 1996. Other animals wandered down into northern Montana and Idaho from Canada.