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WI: Wisconsin wolf numbers have increased as the DNR has implemented a new population model

Paul A. Smith Milwaukee Journal Sentinel

The population of gray wolves in Wisconsin was estimated at 1,195 last winter, a year-over-year increase of 14%, according to the Department of Natural Resources.

The number of wolf packs was up too, from 243 in 2018-19 to 256 in 2019-20.

The data, released Thursday in the “Wisconsin Gray Wolf Monitoring Report, 15 April 2019 through 14 April 2020,” represent a notable increase in wolf numbers after three years of stable counts.

It’s the first time since wolves were effectively eliminated from the state by bounties and unregulated hunting in the 1950s that the native species has officially been tabbed at more than 1,000 animals in the annual winter survey.

The 2019-20 estimate represents the latest chapter of the robust comeback for the wolf in Wisconsin, largely thanks to protections of the federal Endangered Species Act first enacted in the 1970s. The apex predator has shown marked increases in numbers and geographical distribution in the Badger State over the last five decades.

The population of gray wolves in Wisconsin has increased to a modern-era high of 1,034 in late winter 2020, according to estimates from the Department of Natural Resources.

The only substantial deviation was a decline in population observed in 2014 after a three-year period of state management that included a hunting and trapping season.

Wildlife managers at the DNR said at the time the goal of the harvest season was to put “downward pressure” on the state’s wolf population.

In the latest chapter of a see-saw of litigation and management authority over the species, the wolf in Wisconsin and most other states has been protected under the ESA since a federal judge’s ruling in Dec. 2014. The status prevents lethal control of wolves except when human life is threatened.

This year’s Wisconsin report also marks a shift in the method used to describe the state’s wolf population.

The 2019-20 wolf survey is based on an occupancy-based model rather than the territory mapping technique used since 1979.

Whereas over the last four decades state wildlife officials reported a minimum wolf count based on a tracking survey, this year it provided a true population estimate, said Jennifer Price Tack, DNR large carnivore research scientist.

“When the state’s wolf population was much smaller, the territory method was workable,” Price Tack said. “Now, with the larger population, the new approach provides a reliable and more feasible method for monitoring wolves and eliminates the need to try to map every pack and count every pack member.”

A similar occupancy-based model for wolves has been used by wildlife officials in Montana since 2007 and in Idaho since 2009.Get the Coronavirus Watch newsletter in your inbox.

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Wildlife population experts at the DNR and University of Wisconsin-Madison began an effort a couple years ago to customize an occupancy-based model for the Wisconsin wolf population. Glenn Stauffer of the DNR and Tim Van Deelen of UW led the work, Price Tack said. 

The new method still requires hard data inputs, which will be supplied in part by ongoing tracking observations by volunteers, tribal members and DNR staff.

Last winter, the tracking survey covered at least 12,969 miles, according to the report.

A map shows gray wolf packs in Wisconsin detected in a 2019-20 winter tracking survey.

Price Tack said researchers compared data from both methods over the last three years and calculated both the outgoing minimum count using territory mapping and the incoming population range using the occupancy model.

Each year the minimum count fell within the occupancy model’s population range, which is expressed at the 95% confidence level.

For the winter 2019-20, the model showed between 957 and 1,573 wolves in Wisconsin, with the most likely estimate being 1,195 wolves, according to the DNR.

Calculating backward for 2018-19, it found a range of 835 to 1,333 wolves, with the mostly likely estimate 1,047.

The annual report was delayed by about five months this year by a multitude of factors, including personnel turnover, the new model and new smartphone app for its volunteer trackers.

The DNR was without a large carnivore specialist, the person who heads up wolf and bear management, from December when Scott Walter transferred to another position in the agency until early July, when Randy Johnson was tabbed to fill the job.

The smartphone app had some snafus, according to volunteers, and not everyone used it, so DNR staff had a longer than normal process to check the data.

The Department of Natural Resources has adopted a new method of estimating the number of gray wolves in Wisconsin with an occupancy-based model. It replaces a territory mapping technique which produced a minimum count of wolves.

The 2019-20 report found an average of 4.0-4.1 wolves per pack, up from 3.8-3.9 in recent years. An additional 16 non-pack associated wolves were noted.

The annual wolf work is conducted in winter when the animals are easiest to observe and track and when the population is at its annual low.

Forty-eight wolves in Wisconsin are wearing radio- or GPS-collars and being monitored by the DNR, according to the agency.

Wolf numbers roughly double in spring when pups are born then begin to decline through the year due to various sources of mortality, according to wolf experts.

Fifty-two wolf mortalities were detected in the 2019-20 report.

Cause of death could not be determined for eight wolves (15%). For the 44 known-cause mortalities, 38 (86%) were due to humans and six (14%) to natural causes.

Vehicle collisions (40%) and illegal kills (31%) were the leading causes of death for detected mortalities.

General body condition was reported for 25 wolves that were captured during the monitoring period. Twenty-two (88%) were reported to be in good, very good, or excellent body condition, and three (12%) were reported to be in thin condition.

Average weight of seven live-captured adult males was 78 pounds (range 73 to 85), and average weight of three adult females was 71 (range 65 to 77). No mange was reported in any wolf assessed last year in the state.

The DNR’s report comes as the U.S. Fish and Wildlife Service is reportedly close to issuing a decision on wolf delisting in the Lower 48 states.

If wolf management is returned to Wisconsin, the DNR is required by state law to hold a public hunting and/or trapping season. It’s not clear if that could occur this year, but the DNR has been preparing for that possibility, Johnson said.

One of the big unknowns, Johnson said, is the effective date of any delisting rule. It could, for example, take effect after the normal time period Wisconsin has held its wolf harvest season.

And of course, the possibility of another law suit also looms.

For now, the annual report has made at least one thing clear: Wisconsin is home to a healthy wolf population.