DNR Study: The last 2 winters were hard on deer
MARQUETTE – The effects of the past two harsh winters have been bad on white-tailed deer populations in an ongoing study, but ultimately good for the researchers who are involved in the lengthy inquiry to learn more about the mortality of the animals across areas of varying snowfall depths in the Upper Peninsula.
The planned nine-year study is being undertaken by the Michigan Department of Natural Resources in collaboration with the Carnivore Ecology Laboratory at the Forest and Wildlife Research Center at Mississippi State University.
“The study is designed to examine the role of winter weather, habitat and predation on fawn survival across an environmental gradient in the Upper Peninsula,” said Dean Beyer, Jr., a wildlife research biologist with the DNR in Marquette. “Because winter conditions can have strong direct and indirect effects on a deer population, we chose to work across the gradient of snowfall.”
Researchers hope to complete the study over three general snow depth areas, moving from low snowfall to medium and high snowfall parts of the region.
“We completed three years of fieldwork in Phase 1, in the low-snowfall zone and are just starting our second year in the mid-snowfall zone, with one more year scheduled,” Beyer said. “If we are successful in obtaining funding for Phase 3, in the high snowfall zone, we will conduct three years of fieldwork. We would have a one-year transition between Phase 2 and 3.”
The initial low-snowfall zone work began in 2009 in a study area encompassing southwestern Delta County and central Menominee County. The current mid-snowfall zone is situated in an area covering a portion of western Marquette County, southeastern Baraga County, northeastern Iron County and a small section of northwestern Dickinson County.
A significant portion of the study involves capturing female deer, fawns and predators including black bears, coyotes, gray wolves and bobcats.
Does are fitted with radio collars and vaginal radio transmitters, which let researchers know when a deer gives birth. Researchers then quickly find the fawns and place transmitters on them, monitoring their activity, especially over the first three months of their lives.
If the fawns die or are killed, researchers work to determine what caused the mortality. Predators are also monitored after capture to determine where they might be clustering. Researchers want to know how many deer are killed by predators.
During the initial winter of study, researchers discovered one dead fawn after finding 85 bear clusters. However, they found seven dead fawns and three dead adult deer from 57 bobcat clusters. The following winter, 121 bobcat clusters yielded 17 dead fawns and one adult deer, giving researchers new insight into fawn predation.
The study’s most recent quarterly progress report covered the research period of Dec. 16 through March 15. Those results showed 68 deer were captured including 45 adults, 11 yearlings and 12 fawns. Of those deer, 41 females were radio-collared and 40 of those fitted with vaginal implant transmitters.
Eleven deer deaths were investigated, which included eight adult does, two male and one female fawns.
Researchers attributed three of the adult deer deaths to starvation or exposure; two to wolf predation; two to coyote predation; an one to apparent birthing complications. Two of the fawn deaths were thought to have been caused by apparent starvation or exposure and the third was attributed to predation by coyote.
Beyer said it’s too early to make meaningful comparisons between the low and mid snowfall zones, with only one complete season logged in the middle zone.
“However, the purpose of working across the environmental gradient is to capture the range of variability in conditions,” Beyer said. “The severe conditions in the last two winters are important in that they ensure we are getting one end of the continuum.”
As an example, Beyer said the extended winter of 2012-13 resulted in the lowest apparent fawn survival for the four years of the study so far.
“With the severe conditions this winter, the apparent mortality rate of adult does is the worst we have documented during the study,” Beyer said. “So, the past two winters have been bad for deer, but in the long run, likely good for our understanding of this complex ecological system.”
The recent progress report said six male and eight female adult black bears were immobilized in their dens, along with three male and one female yearlings. Twelve cubs were observed from five females.
Three bobcats were captured and collared. To estimate bobcat abundance, hair snares were set up along with remote cameras at 64 sites. A total of 179 hair samples were recovered and more than 620,000 camera images.
In the mid-1990s, the U.P. experienced two back-to-back record snowfall winters, which dramatically impacted the region’s deer herd. The ongoing DNR-Mississippi State study is part of a subsequent effort to try to determine why the deer population has not rebounded as successfully as was expected after those severe seasons.
At the National Weather Service office in Negaunee Township, a total of 251.4 inches of snow fell during the winter of 1995-96, followed by 272.2 inches of snow in winter 1996-97. This winter’s snowfall has totaled 195.3 inches, 7.3 inches below normal. However, there were 79 consecutive days below freezing and frost reached depths of eight feet into the ground in some areas.
A DNR Review of Deer Management in Michigan said about 200,000 died in the U.P. during the winter of 1995-96, about a third of the total. The review said even in mild winters, a loss of 10 to 15 percent of the winter deer herd is not uncommon in the region. Of the deer dying in severe winters, the review said about two-thirds are fawns, aged 8 to 11 months old.
Safari Club International and its Michigan Involvement Committee have provided significant support for the ongoing winter study project. Other groups in the region have also contributed to the project.
To learn more about the study, or to review past progress reports, videos and research photographs, visit: www.fwrc.msstate.edu/carnivore/predatorprey/index.asp.
John Pepin can be reached at 906-228-2500, ext. 206. His email address is firstname.lastname@example.org.