MILWAUKEE — A University of Wisconsin-Madisonstudy shows the human toll on wolves is higher than previously estimated and that state officials have underreported wolf deaths in past analyses.
For years, wolves have been shot illegally, struck by cars and trucks or legally killed by authorities acting on reports that wolves were killing and threatening livestock and pets.
But in a study published Monday in the Journal of Mammalogy, UW researcher Adrian Treves and a group of scientists found higher levels of illegal killing of wolves in Wisconsin than reported by the Department of Natural Resources.
As part of the study, the researchers reinvestigated fatalities of a subset of wolves and found “abundant evidence” of gunshot wounds and injuries from trapping that may have been overlooked as a factor in their deaths, the authors said.
The study is likely to be controversial. As wolves have recolonized and their population has grown to an official count of nearly 900, the debate over their impact has only intensified.
Treves, for example, has been a critic of the design of the state’s hunting and trapping season for wolves and its potential to damage a healthy wolf population over the long term.
In an open letter in November 2015, Treves was one of more than 70 scientists and wolf experts who said studies show citizens are more tolerant of wolves than commonly assumed. The scientists questioned whether wolves can sustain their populations under state hunting and trapping seasons.
Adrian Wydeven, a retired DNR wolf ecologist, who read an advance copy of the study, disagreed with aspects of the research, including Treves’ interpretation of DNR data.
The study “seems to suggest … intent by (the DNR) to under-report (poaching) when it really just represents use of different models or agency reporting raw data,” Wydeven said in an email to several wolf experts that was shared with the Milwaukee Journal Sentinel.
“We always tried to report exactly what we found in the field,” Wydeven said in an interview.
Wydeven retired from the DNR in 2015 and is coordinator of the Timberwolf Alliance at Northland College in Ashland.
In a statement, DNR spokesman Jim Dick said: “While the (DNR) data collected is useful in determining wolves killed, that’s not its intended purpose. The data collected is meant to determine population and such things as pack territories. Wolf mortality numbers are based on actual dead animals detected.”
Treves said he and his fellow researchers examined the DNR’s methodology and are not claiming that officials are purposefully underestimating wolf deaths.
In the paper, the researchers say that failing to accurately account for wolf deaths, especially in future hunting and trapping seasons, is “risky.” Also, if officials continue to underreport poaching, it “will risk unsustainable mortality and raise the probability of a population crash,” they write.
“My argument is that scientifically you have to put your best foot forward,” said Treves, founder of the Carnivore Coexistence Lab at UW-Madison. “And when the DNR didn’t, they were doing it with an illegal activity (poaching).”
The UW study investigated the deaths of 937 gray wolves from October 1979 to April 2012 — a period that ends before Wisconsin initiated hunting seasons for wolves. Of the 937 wolves that died and whose deaths were investigated, 431 wore radio collars.
The UW researchers said that their analysis showed that the death of radio-collared wolves attributed to human causes was 64%. But the DNR calculated 55% and said an additional 18% of deaths were due to unknown causes, according to a DNR report in 2012.
Said Treves: “That’s a big number. We dug deeper and maybe it’s poaching.”
The researchers re-examined government records of necropsies and X-rays and found in some instances that gunshot wounds were a factor in the cause of death when other causes were cited.
But the study said that figure lends credibility to the researchers’ claim that more wolves have been subject to poaching than the DNR reported.
Julie Langenberg, one of the authors of the study and a former DNR veterinarian, re-examined wolf death records.
She found evidence of gunshots that in the initial analysis were either mentioned briefly or not identified. Sometimes it was her own work.
“You are not looking at alternative facts,” Langenberg said of her review of wolf mortality in the study. “You are looking at the same facts, but because you are asking different questions, you are doing a different kind of assessment.”
She said the DNR’s job was to simply determine the cause of death.
Wisconsin officials reported that 528 wolves were killed during the state’s wolf hunting seasons in 2012, 2013 and 2014.
During 2013, 257 wolves were killed — nearly half of all wolves harvested during the three years. Then the wolf population dropped 18% from 809 in 2013 to 660 in 2014.
The hunts were halted in December 2014 by a federal judge who said Wisconsin, Minnesota and Michigan were violating the Endangered Species Act. This year, Congress, including Republicans and Democrats from Wisconsin, introduced a bill to replace federal protections with state management.