Oregon wildlife troopers found five dead wolves in February, then a sixth in March, a seventh in April and an eighth in July.
By then, they knew the animals were killed by poisoning. Now, the state police are pleading with the public for help, saying that the authorities have “exhausted leads in the case.”
The Oregon State Police last week urged anyone with tips or information about the poisonings to contact them, after months investigating the killings.
All five wolves in a group called the Catherine Pack, found southeast of Mount Harris in Eastern Oregon, and three wolves from other packs were among the animals killed, the State Police said in a news release on Thursday.
The police declined to say what substances were used. They did not say whether they believed the poisonings were deliberate or what might have motivated them.
It is illegal to shoot wolves in Oregon, except in defense of human life and in some situations related to livestock depredation, according to Michelle Dennehy, a spokeswoman for the Oregon Department of Fish and Wildlife. Oregon does not allow any hunting of wolves at this time, she said, adding that penalties for wildlife crimes could include thousands of dollars and jail time, depending on the charges.
“The poisoning of an entire pack is significant,” Ms. Dennehy said. She said her department would have a clearer picture of how the deaths might have affected the overall population of wolves next year, after biologists complete their winter surveys over 2021-22.
News of the deaths concerned regional and national wildlife advocates, especially as the topic of wolf hunting has become a conflict in states like Wisconsin, where hunters killed more than 200 wolves in less than 60 hours this spring. In the courts, federal officials and wildlife advocates are clashing over protections.
Maggie Howell, the executive director of the Wolf Conservation Center, an environmental nonprofit, said the Oregon case was “pretty unusual,” adding “the illegal killing of wolves every year remains a big concern.”
As wolf populations have slowly increased over decades of protection, debate has returned over the extent of their recovery, the laws about them and their effect on ranching and hunting.
Wolves were sometimes treated as a type of “political predator,” Ms. Howell said. “People love them. People hate them,” she added. “They definitely evoke a lot of emotions.”
Ms. Howell said that the loosening of protections, such as the delisting of the wolf from Oregon’s endangered list in 2015 and from the federal list this year, could have played a role in the Oregon case.
“Peer-reviewed research shows that poaching worsens when legal protections for wolves are relaxed,” she said.
Environmentalists have condemned the decision to take wolves off the federal endangered species list, calling it premature. Federal officials have argued that gray wolves’ population have reached conservation goals and are resilient enough to withstand some hunting.
In Oregon, state wildlife biologists counted 173 wolves in Oregon last winter, a 9.5 percent increase over last year’s count of 158, according to Ms. Dennehy, the Fish and Wildlife spokeswoman. Ms. Howell said that although the gray wolf population had been slowly increasing since the discovery of a pack in 2008, “all but three wolf packs are in northeast corner of the state, which is a small fraction” of the wolf’s historical range in Oregon.
This year’s investigation began on Feb. 9, when troopers from the Oregon State Police Fish and Wildlife Division received information from the Oregon Department of Fish and Wildlife about a tracked wolf that might have died.
When the troopers responded to the scene, they found three dead male wolves and two dead female ones — wolves later found to be members of the Catherine Pack, named because of their range in the area of Catherine Creek in northeastern Oregon. A dead magpie was also found near the wolves.
The animals were taken to a state’s forensic lab to determine their cause of death.
On March 11, troopers learned that another wolf’s collar had pinged a “mortality signal”: Its collar had been still for many hours, suggesting the animal was likely dead. Officials found a dead female wolf, along with a dead skunk and magpie nearby. Their remains were taken to a lab for testing.
As snow melted and harsh weather receded, the troopers found evidence that they suspected was linked to poisoning, and they had it submitted for testing.
In April, lab reports confirmed that poisoning was the cause of death for the six wolves, the skunk and two magpies, the police said. That same month, a male wolf was found dead from another group, called the Five Points Pack. In July, a young female wolf from another pack was also found dead.
“Toxicology reports confirmed the presence of differing types of poison in both wolves,” the police said.