The groups say inadequate state management plans are partly to blame. The Humane Society's Dave Pauli says Idaho's plan seeks to reduce its population from 800 to 100 wolves. Pauli says if that continues, the survival of the grey wolf population will soon be in jeopardy.

"The delisting was a victory; it was a celebration of the protection of the species. It shouldn't be the opening of an open season on them," said Pauli. Officials say since the delisting took effect on March 28, nearly three dozen wolves have been killed in Wyoming alone.