Underreporting Wolf Poaching
by Cat Urbigkit, Pinedale Online!
February 9, 2017
A Wisconsin researcher and his colleagues have released a new paper alleging that the Wisconsin Department of Natural Resources has vastly underestimated the number of wolves that die from illegal poaching. The paper, Gray Wolf Mortality Patterns in Wisconsin from 1979 to 2012, was published in the Journal of Mammalogy, with Adrian Treves as the primary author.
Lee Bergquist of the Milwaukee Journal Sentinel notes that Treves has been a critic of the state’s wolf hunting and trapping seasons. Bergquist’s article (linked below) notes that retired wolf ecologist Adrian Wydeven disagrees with Treves’ interpretation of the DNR data. Although some may assume that the DNR intentionally under-reported poaching, the Treves research "really just represents use of different models or agency reporting raw data," Bergquisst reported.
Treves and his team reassessed wolf mortality data and came up with a different interpretation of that data than did DNR, using a variety of modeling and new estimates and assumptions. The paper claimed that by correcting sampling and measuring biases, the authors were able to "reconstruct the numbers and causes of some wolf deaths that were never reported." The authors report that one-half of all poached wolves went unreported, and that mortality rates were substantially higher for unmonitored wolves than for monitored wolves.
The authors also reclassified wolves that had died from other events, such as vehicle collisions, or mange, if those animals had evidence of previous gunshot wounds. The authors noted, "Therefore, the vast majority of poaching was by gunshot and more than one-
third of collisions were associated with some old or recent gun-
shot, which might have been perimortem. The latter suggest vehicles might have been used as weapons."
Thirty-five percent of the animals that had been necropsied were reclassified for cause of death. For example, one wolf classified as dead from sarcoptic mange by DNR was reclassified as poached because the necropsy found that the wolf had had two previous traumas that predisposed it to developing severe mange – an injury to a foot associated with being trapped six months prior, and an injury to its back "apparently associated with being shot" some time before. According to the paper, "We reclassified the wolf as poached because it was debilitated by illegal trapping and gun-
shot."
Another wolf that was killed by a vehicle collision was reclassified as poached because it had a healed minor gunshot wound that might have predisposed the wolf to the collision.
Another wolf found dead at a road intersection had fractures in its hindquarters compatible with vehicle trauma. It also had a fatal gunshot wound in the head "which might have reasonably been done to ‘put it out of its misery’" but since there was no confirmation that this was done, the authors reclassified the wolf as poached.
Treves is also the author of a controversial paper released last year entitled "Predator control should not be a shot in the dark." {See link below.}
Here are some of the paper’s highlights, according to Treves’ UW-Madison Carnivore Coexistence Lab:
• We investigated causes of death of 937 gray wolves in Wisconsin from October 1979 to April 2012. We discovered that poaching (illegal killing of wolves) was the most common cause of death. We documented that wolf population growth slowed by 4% in each of the last few years as a result of increased mortality. Our results cast doubt on the adequacy of state regulatory mechanisms to protect wolves and the quality of science used to set policy.
• From 431 deaths and disappearances of radiocollared wolves aged > 7.5 months, we estimated human causes accounted for two-thirds of reported and reconstructed deaths, including poaching in 39–45%, vehicle collisions in 13%, legal killing by state agents in 6%, and nonhuman causes in 36–42%. Poaching risk for wolves without radio collars appears to have been even higher. There is a list of 504 reported deaths for non-collared wolves but it’s not easily comparable.
• When the government did recover wolf carcasses, the agencies systematically under-estimated poaching by more than 5% and probably more than 11%. Two forms of scientific bias (defined as non-random errors) explain the systematic under-estimation. The first – sampling error – occurred when the government radio-collared wolves in core areas of the wolf range where wolves experience less mortality overall and especially less human-caused mortality. We also found measurement error when poaching was missed by the agency and assigned to another cause of death. For example, a subsample of radiographed wolf carcasses revealed that 37% of vehicular collisions also included metal consistent with gunshot wounds.
• We reconstructed the fates of missing wolves and estimated that wolves without radio-collars experienced 28% higher rates of mortality (per capita hazard) than did radio-collared wolves. The finding that radio-collared wolves suffered lower rates of mortality and the risk of poaching was systematically under-estimated, will present a scientific challenge because official estimates of population dynamics based on radio-collared wolves are inaccurate a by sizable margins.
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