Written by Glen Schmitt
Times outdoors writer
This past winter, wildlife officials with the Minnesota Department of Natural Resources conducted a survey of the state’s wolf population. It was the first such study done since 2008, at which time the wolf population was estimated to be in the 2,900 range.
The DNR announced results from this past winter’s survey earlier this week. It showed that Minnesota’s wolf population had dropped 710 wolves from five years ago, but left researchers confident that numbers remain firmly established across the wolf range.
The most recent survey reflected an estimated population of 2,211 wolves across the northern-forested region last winter. That total consisted of 438 packs and the overall population estimate remains the highest in the lower 48 states.
Dan Stark, DNR large carnivore specialist, said it’s worth noting that the survey data was collected during the middle of winter, before pups were born.
Even if half of the pups born since the survey don’t make it through the summer months, the wolf population heading into this fall will likely exceed 3,000 animals.
“The results of the survey show that Minnesota’s wolf population is fully recovered,” Stark said. “The once-threatened status of the population is responding naturally to the availability of deer, wolves’ primary food source.”
Despite a lower estimate than 2008, the current population is above the state’s minimum management goal of at least 1,600 wolves. It’s also well above the federal recovery goal range of 1,251 to 1,400 wolves.
Decline in numbers
The decline in total wolf numbers was likely the result of several contributing factors, according to John Erb, research biologist with the DNR.
Erb noted territorial changes, prey opportunities, and the first regulated wolf hunt in the state last fall as parts of the equation.
While the overall occupied range of wolves didn’t change that drastically, the average wolf pack territory size jumped to 62 square miles, up 13 percent from the last survey. The increase in territory size was likely caused by fewer deer per square mile, which were reduced by design, as much as 25 percent in the forested region since the 2008 survey.
“The average pack is using more land than in the past because deer density has declined,” Erb said. “They’re utilizing more area to find prey than we’ve seen, but that’s expected.”
The average number of wolves per pack decreased by 12 percent since 2008, down from 4.9 to 4.3. But Erb says that too can be contributed to a decline in prey, moderate winter weather that made it difficult for wolves to catch deer, and the wolf harvest that took place prior to last winter’s survey.
Hunters and trappers took 413 wolves last season during the state’s first regulated and somewhat controversial harvest season. Also adding to the population decline was the fact that over 200 wolves were taken via livestock depredation complaints.
“I would say it’s obvious with the (hunting and trapping) harvest just before we did our count that we expected population estimates to be below 2008,” Erb said. “But it was not the only contributing factor.”
Stark agreed, noting that wildlife officials projected the wolf population prior to last fall’s hunting and trapping season to be around 2,600 animals. He also pointed out that the influence of a harvest season only diminishes the population on a short-term basis.
Hunting, trapping
The DNR expects to hold another hunting and trapping season this fall. The agency will use the current survey data to help establish framework for the upcoming season, which will likely include a lower harvest quota than last year.
Stark said details on the hunt, including a harvest target will be available late in July or early August. A proposal is in the works for the upcoming season that will continue to closely monitor and regulate the harvest of wolves in order to ensure that human-caused mortality will not exceed safe levels for long-term population sustainability.
“Data from the wolf harvest is well supported and the population remains resilient and highly reproductive,” he said. “This survey showed wolves are still widely distributed, we’re seeing expansion to the west and south, and we remain confident that we can manage a regulated season without minimizing the population.”
Those in favor of continuing a wolf harvest season have suggested that the state’s population estimates have been too low in the past. Based on depredation complaints, general sightings, and the gap between population surveys there is some anecdotal belief that wolf numbers could have been higher than expected in recent years.
Erb says there may have been some signs that the population could have been greater a couple years ago than initially thought, but he didn’t suggest that the state had over 7,000 wolves at any one time.
In addition, there’s always some margin of error when populations of a specific animal are counted. For the most recent survey, there was a plus/minus of 500 animals, but Erb is confident with the population estimate established this past winter.
“These survey results don’t validate or invalidate past results, it stands alone and makes biological sense,” he said. “I think our estimates have been pretty reliable, keep in mind it’s a mid-winter survey and I stand by our numbers.”
The only real comparison between the present and past wolf population estimates is that they have been conducted during the same time period over the past 40 years. Erb added that it’s done during the winter because wolves are easier to count and that it would be nearly impossible to do so any other time of the year.
Hunting opposition
Opponents to the wolf hunt aren’t so comfortable with the current population estimates and some groups continue to show frustration with the DNR for continuing hunting and trapping the animals.
With an estimated 25 percent drop from the last time the survey was conducted, there’s a general feeling among most animal rights groups that wolves continue to struggle and they have not fully recovered as much as state and federal officials believe they have.
Dr. Maureen Hackett, founder of Howling For Wolves, will continue to oppose any hunting or trapping. After the survey results were announced on Tuesday, she said there is still no scientific reason to harvest wolves.
Earlier this spring, her organization along with several others, took their opposition to the wolf hunting season and challenged it in the Minnesota Court of Appeals. The Court rejected those efforts on the basis that they couldn’t prove the DNR had caused damage to the wolf population by implementing a season.
“We are disappointed that the survey shows a significant decline in the Minnesota wolf population,” Dr. Hackett said. “This is a strong indication that we can’t afford another recreational wolf hunting and trapping season.”
She added that Howling For Wolves is committed to finding non-lethal solutions that minimize conflicts with wolves and increase tolerance in Minnesota for the predators.
Hackett says wolves are valued by the vast majority of Minnesotans and that they don’t need to be hunted.
Stark said the DNR will continue to monitor pack and territory sizes over the next few years. This will include more frequent radio collaring of wolf packs that will provide additional information on the population’s response to wolf season harvest.
Detailing Minnesota’s wolf population survey
According to historical records from the Department of Natural Resources, estimating Minnesota’s wolf population was a crude endeavor decades ago. It often involved nothing more than bounty records or anecdotal information, which was more out of necessity than it was accurate.
With advancements of radio telemetry, improved geographical information and global positioning systems, wildlife officials have been able to monitor and map wolf numbers more accurately.
Since the late 1970s, Minnesota has monitored its statewide wolf population using a combination of territory mapping and an ad hoc approach to determine the total area occupied by wolves. These methods have not changed much over the past 40 years.
Population surveys were conducted every 10 years from 1978 to 1998, and every five years since. Results indicated a wolf population that was expanding both geographically and numerically through the late 1990s, with limited expansion through 2007.
The most recent survey conducted last winter, prior to wolf pups being born, reflected a population that declined slightly from the same survey conducted five years ago. But the population remains strong and is deemed by DNR officials as fully recovered in the state.
When dividing the estimated occupied range — which has shown expansion to the south and west from traditional wolf boundaries — by average territory size, wildlife researchers estimated that 438 wolf packs roam Minnesota, or 13 percent fewer packs than in the winter of 2007-08.
By multiplying the average pack size (4.29) and accounting for an estimated 15 percent lone wolf average, the population estimate comes out to 2,211 wolves. The confidence interval ranges from 1,652 wolves on the low end to 2,640 wolves on the high end, with a plus/minus factor of 500 animals.
The current population estimate is 700 wolves fewer than 2007. But the confidence interval for the current population estimate overlaps the confidence interval from 2007, which means the population is not that much statistically different.
However, the totality of last winter’s survey information — which included lower prey densities, larger wolf pack territory, smaller pack size and limited opportunity for any population response following a hunting and trapping season — indicates the 2012-13 mid-winter population was lower than the estimated population during the 2007 survey.