EDITOR'S NOTE: This story was provided by the Michigan Department of Natural Resources and Environment as an update to a research effort begun in the southern part of the Upper Peninsula in 2009. The DNRE is committed to the conservation, protection, management, and accessible use and enjoyment of the state's environment, natural resources and related economic interests for current and future generations.
MARQUETTE - If just the name of the study - "Role of Predators, Winter Weather and Habitat on White-Tailed Deer Fawn Survival" - seems like a mouthful, you can imagine how complex the study is.
It is complex. The Department of Natural Resources and Environment, in collaboration with Mississippi State University, is in the midst of what might turn out to be a long-term study that is attempting to quantify which factors influence fawn survival. And there are a lot of questions.
A fawn on Presque Isle park scratches. (Journal photo by Taylor Jones)
"The big picture is, we know the factors that influence deer vary along a latitudinal gradient in Michigan," explained Dean Beyer, an Upper Peninsula wildlife research biologist. "Michigan is a long state - more than 300 miles north to south. Winter weather is not that big a factor in southern Michigan, but it can be an important factor in the Upper Peninsula. In order to do a good job managing deer we need to understand how those factors vary across the landscape."
Beyer said he's seen studies in southern Michigan that show over-winter survival of up to 75 percent of fawns, yet by comparing fecundity rates of U.P. does with hunter sightings of fawns, the survival rate of fawns - from birth to hunting season - in the U.P. appears to be less than 50 percent.
"The fundamental question," Beyer said, "is: 'What the heck is going on here?' "
So is it predators? It's not that simple.
"Predator-prey relationships are really complex," said Beyer, who is working with faculty and graduate students from Mississippi State University to try to get the bottom of the issue. "There is general agreement in the scientific community that you see predators limiting prey populations most often when there are multiple predator species in the system.
"When you look at the U.P. we've got four predators that routinely target deer bobcats, coyotes, wolves and bears."
The study began is the southern Upper Peninsula in what Beyer calls "the low snowfall zone." And the study is looking at a variety of factors, including weather and habitat.
"We started this in 2009 when we began trapping deer in the winter time," Beyer explained. "We'd catch does, determine whether they were pregnant (with an ultrasound) then, if they were pregnant, fit them with vaginal implant transmitters and standard radio collars."
When the doe delivers a fawn, the transmitter drops, too. The temperature-sensitive transmitter begins sending out as different signal, alerting researchers to the birth.
"We can tell within a half hour of when the fawn was born," Beyer said. "You want to get in on these fawns as quickly as possible - a lot of bad things can happen to fawns within their first few days of life."
Essentially, crews go to the transmitter site and begin looking for fawns. Any fawns that are found are outfitted with expandable-collar radio transmitters
"We monitor those fawns very frequently during their first three months of the life," Beyer said. "If they die, we try to go in and determine what their cause of death was."
That's the prey part of the equation.
"We're also coming at this from the predator perspective," Beyer said. "We capture bears, wolves, bobcats and coyotes, fit them with GPS collars, and set them up to collect locations very frequently during fawn drop and early growth stages. We look for clusters of locations places where a predator spent a significant amount of time and search the clusters (often with a dog) for kill sites.
"We're trying to estimate the number of fawns that are killed by these different species of predator," Beyer continued. "That's hard to accomplish in the summer. These collars give us a tool to estimate what predation is in the summer months."
What researchers have found, so far, is not what you might think they'd find.
For instance, the first year, researchers searched 85 bear clusters and found one dead fawn. But searches of 57 bobcat clusters turned up seven fawns (and three adult deer). So the researchers redoubled their efforts the following year and searched 121 bobcat clusters. They found 17 dead fawns and one adult deer.
"It's surprising to a lot of folks that bobcats are such an efficient predator on fawns," Beyer said.
Oddly enough, a study in Minnesota found the same thing, Beyer added. But knowing the rate that various predators kill fawns is only part of the equation; knowing the abundance of the predator species and the abundance of deer will clarify the picture.
In addition to checking the clusters, researchers are doing all sorts of vegetative studies at mortality sites, birth sites and cluster sites - to see if there's a habitat component to the predation - as well as doing diet analysis of predator scats.
Why? Researchers are trying to see if the availability of alternative prey species - (turkey, grouse, snowshoe hare, beaver, etc.) reduces predation on deer fawns. The project incorporates a number of methods for gauging the relative populations of alternative prey species to see if predation on those species increases as they become more available.
The first phase of the research project is scheduled to run for one more year, Beyer said. Then, depending on the availability of funding, Beyer hopes to conduct the same sort of research in medium snowfall locations (he's already scoping out potential study sites) and then high snowfall locations.
The research is being funded through a variety of sources. The Safari Club International Foundation is a big player, as is its SCI's Michigan Involvement Committee and SCI's Northwoods Chapter. Donations have also come in from UP Whitetails of Menominee County and Wildlife Unlimited of Delta County. And, of course, federal funds that are matched with state funds are being used.
Michigan's Upper Peninsula deer population crashed hard after difficult winters in 1995 and 1996 and the population has not responded in the following 15 years in the way many had predicted it would. So is the culprit predation? Habitat? Weather? Odds are it is some combination of the three. And that's what this research project is designed to find out.