BOVINE TB: Aerial survey shows drop in deer numbers

After several years of aggressive removal efforts, deer numbers continue to decline in the core area of a minor bovine tuberculosis outbreak near Skime, Minn., but more culling is scheduled to begin later this month.

After several years of aggressive removal efforts, deer numbers continue to decline in the core area of a minor bovine tuberculosis outbreak near Skime, Minn., but more culling is scheduled to begin later this month.

And this time, crews plan to expand the cull to an area just west of the core, where a 3ยฝ-year-old whitetail buck tested positive for the disease last fall. It was the first positive case to be found outside the core since 2005, when the disease was detected in cattle herds, and later deer, near Skime.

According to Michelle Carstensen, wildlife health program coordinator for the Minnesota Department of Natural Resources, deer populations in the core are estimated at 422, down from 664 last year and 807 in 2008, based on an aerial survey conducted in late January. As part of the survey, crews flew part of the core area and then used the deer count to develop an estimate for the entire core, which covers 164 square miles.

The first aerial survey, in 2007, produced an estimate of 935 deer in the core.

"We're seeing a decreasing trend," Carstensen said. "There isn't always year-to-year significance, but there was between last year and this year."


Still, Carstensen cautions against reading too much into the latest estimate.

"It's a snapshot in time," she said. "It doesn't mean there's going to be 422 deer in the core tomorrow. It's a fluid environment.

"For what they counted, it's a good sign deer numbers are going down in that critical area. I was happy to see that trend going down. There's been just an immense amount of pressure, yet there's deer still there."

The DNR has focused on removing deer from the core and testing for bovine TB in an effort to reduce the opportunities for further transmitting the disease, which can spread by close contact. The DNR has sampled more than 7,500 deer since 2005, and 27 have tested positive for the disease.

Expanded area

Carstensen said aerial crews also flew transects in a two-mile radius around the area where the buck last fall tested positive for TB. While not part of the formal survey, crews counted 300 deer within the expanded area, which lies two miles west of the core, Carstensen said.

And in one section of private land with standing corn, Carstensen said the crews counted 190 deer.

"It's concerning that deer in that area are in higher numbers than we'd like to see congregated," Carstensen said. "If there's a disease that's still existing in deer, that's a perfect time for it to be spread and transmitted as they're congregated in standing corn."


Carstensen said the DNR and federal sharpshooters from the U.S. Department of Agriculture now are working to gain access to the private lands in the area west of the core.

"It's a whole new set of private lands," Carstensen said. And as was the case in the core area, not all of the landowners approve of the culling effort.

No aerial shooting

Carstensen said this winter's sharpshooting campaign could last into April if the crews continue to kill deer but could end earlier if there aren't enough animals to justify the effort.

One thing's for sure, Carstensen said -- there won't be any aerial sharpshooting this winter.

"The numbers are down enough, and we know of only one positive from the fall, so that's a positive trend, and the chopper is extremely expensive," Carstensen said. "We don't think we need to go that extra level, given the trend."

Carstensen said the DNR sampled almost 1,500 deer this fall in the core and adjacent areas during the various hunting seasons. The goal, she said, was to sample 1,500 deer in a larger area outside the core but that effort fell short by about 500 deer. The hope, she said, is that the sharpshooting campaign will bring that number closer to the target.

"We want to keep seeing less and less infections," she said. "It would be great to get through this sharpshooting season and not have any surprises."


Dokken reports on outdoors. Reach him at (701) 780-1148; (800) 477-6572, ext. 148; or send e-mail to .

Brad Dokken joined the Herald company in November 1985 as a copy editor for Agweek magazine and has been the Grand Forks Herald's outdoors editor since 1998.

Besides his role as an outdoors writer, Dokken has an extensive background in northwest Minnesota and Canadian border issues and provides occasional coverage on those topics.

Reach him at, by phone at (701) 780-1148 or on Twitter at @gfhoutdoor.
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