Wolves have killed a cow calf and a horse near Pinedale, the first livestock deaths caused by wolves this year.

U.S. Fish and Wildlife Service officials say wolves from the Black Butte pack killed the calf at a ranch in mid-March. Agents then killed three wolves from the pack — a radio-collared adult, a pup and a yearling.

They say wolves from the pack attacked horses at another ranch last week. One horse was killed and another was injured.

Officials believe there are probably two wolves left in the pack and they plan to put them down.

Wolf management project leader Mike Jimenez believes the pack is the same one that killed about 37 sheep and a steer last summer. He says two-thirds of the state's packs don't cause chronic problems.

Copyright 2010 The Associated Press.