(Salem, OR) -- Environmental groups are pulling out of negotiations over Oregon's plans for wolf management. The Oregonian reports that the groups are concerned about when and how livestock owners can kill wolves. Four organizations have joined to send a letter to Governor Kate Brown after getting a look at a draft of the plan before Christmas. The letter claims that every amendment they have proposed has been rejected by the Oregon Department of Fish and Wildlife. Ranchers say the wolves prey on their livestock, while environmentalists say the animals are an important part of the ecosystem.