Fairbanks, Alaska - State officials have begun issuing permits for aerial hunters to kill wolves in parts of Alaska in an effort to boost moose and caribou populations.

The first pilot-gunner teams killed four wolves last week after the Alaska Department of Fish and Game began issuing the permits earlier this month. More hunters are expected to take to the air beginning Wednesday.

Officials want to cull about 500 wolves in various parts of the state to control their numbers this winter.

Alaska's wolf population is estimated at 8,000 to 11,000 and hunters and trappers kill an average of 1,500 a year, officials said.

The aerial hunting program is being met with protests by several wildlife advocacy groups.

Friends of Animals, based in Connecticut, is organizing a tourism boycott of Alaska and ''howl-in'' demonstrations in more than two dozen cities. The group organized a similar campaign during last year's aerial hunting campaign.

Washington-based Defenders of Wildlife, meanwhile, has petitioned U.S. Interior Secretary Gale Norton to halt the program under the Federal Airborne Hunting Act.

The group is also collecting signatures on a petition to send to President Bush.