By Richard P. Smith
Coyotes aren’t the only predators impacting fawn survival rates.
It’s about time black bears get the credit they deserve as whitetail predators. On a year-round basis, where they are present, bears might not kill as many deer as coyotes or wolves, but if you focus on which predator takes more fawns, bears are right at the top. And if you assume black bears don’t prey on adult deer, guess again.
Where black bears are common, as they are in Michigan’s Upper Peninsula (UP), northern Wisconsin and Minnesota, they’re deadly on fawns, often taking more than the much more common coyotes.
A fawn survival study has been under way in the UP for a number of years. As part of the study, a sample of pregnant does are live-trapped each year and fitted with GPS collars. The researchers also put collars on as many of the fawns as possible soon after they are born. They then try to document the cause of death of collared fawns.
Most fawns are born in June. By late August 2014, seven collared fawns had died. It was determined that bears killed four, and one each was preyed upon by a coyote and a bobcat. The identity of the predator that killed the seventh fawn is unknown. That means bears were responsible for at least 57% of the fawn mortality documented during the first months of the collared fawns’ lives.
Black bears accounted for a similar mortality rate of collared fawns during a study conducted in Wisconsin’s Chequamegon National Forest. During that study, 45 fawns were fitted with transmitters in the same area where 52 bears were wearing radio collars. Bears were responsible for seven out of 12 fawn deaths (58%). Coyotes only accounted for the loss of three fawns.
The loss of four or seven fawns to bears during the course of a year might not seem significant, but the results of those studies are a small part of the picture. Those studies only document a fraction of the number of fawns killed by bears (as well as other predators) in the study areas.
Dr. Lynn Rogers from Ely, Minnesota, pioneered a unique approach to studying black bears that involves habituating study animals to the presence of people so researchers and volunteers can walk with the bruins to observe their behavior. One adult female black bear that was part of that study was observed eating six fawns during the course of one fawning season in northern Minnesota, where deer numbers are already low.
Over a five-year period (1986-1990), fawn predation by five habituated bears was monitored. Each bear at least one year old preyed upon an average of two fawns per year.
Terry DeBruyn, now the forest ecologist with the Hiawatha National Forest in the UP, also walked with some of his study bears in the UP’s Alger County, and he observed bears taking multiple fawns each year, too. The most fawns a single bear killed during one year was six.
I was a volunteer helping DeBruyn during his study, and I was with him and his bears on two occasions when the bears killed fawns. I was with him when he documented the first instance of a study bear preying on a fawn. The date was July 10, and we were walking with an adult female that had three cubs.
At one point, the bear stepped up on a fallen tree and then pounced on a fawn that was hiding next to the trunk. That fawn was more than 30 days old. Most fawns killed by black bears are less than two weeks old. That’s when fawns rely on hiding rather than running and are most vulnerable. But when bears catch fawns that are more than 14 days old by surprise, like the one we observed, they will take advantage of the opportunity.
Black bears are primarily opportunistic feeders, meaning they don’t actively hunt whitetail fawns, but stumble upon them during their everyday travels. A couple of things about the biology and life history of black bears increases their tendency to stumble upon newborn fawns, however.
The bear breeding season, for example, coincides with peak fawning across most of North America. Black bears begin breeding during late May, with the peak normally in June and activity continuing into July and August. Adult males travel widely in search of receptive females during this time. It’s not unusual for them to stumble upon fawns during those travels.
Mother black bears also separate from their yearlings when the cubs reach 1 1/2 years old. That’s usually during late May or early June, just prior to breeding. Yearlings that separate from their mothers often cover a lot of ground when they disperse from her territory, and this is especially true of males. Dispersing yearlings frequently stumble on fawns and are just as capable of killing them as adults.
In fact, yearlings may even be more efficient predators of fawns than older, larger bears because they can run faster and are more agile.
Retired Michigan Department of Natural Resources deer researcher John Ozoga was one of the first to document how much impact black bears can have on fawns. He was studying whitetails in a 1-square-mile enclosure at a research facility in the UP.
Yearling black bears got in that enclosure twice while fawns were being born. One of the yearlings weighed 100 pounds, and the other was 66 pounds. Both times black bears got in the enclosure, they increased fawn mortality on that square mile by 22%. Ozoga trapped both bruins to remove them from the enclosure, but he reported that one of them killed as many as nine fawns before he was able to catch it.
Although most fawn predation by bears is opportunistic, older bruins that have had experience catching fawns often get better at it simply because they know what to do when they encounter a fawn. They also learn where and when they’ve found fawns in the past, which helps them locate more in the future.
Experienced bears learn to associate the presence of adult does with the availability of fawns at certain times of year, too. Terry DeBruyn said the older female he walked with searched for fawns on a number of occasions after she encountered an adult doe.
The Quality Deer Management Association’s Kip Adams explained his experience with how much impact black bears can have on fawn survival in Pennsylvania in the QDMA’s 2015 Whitetail Report. Adams manages a 700-acre farm on which bears are abundant.
“We have a lot of coyotes, a lot of bears and a lot fewer deer than in the past,” he wrote. “During 2002 and 2003, hunters on the farm averaged seeing 3.5 deer per hour. The last three years, they’ve averaged seeing .8 deer per hour, a 77% reduction.”
Bears are so abundant that hunting camps in his area are now taking more bruins than bucks. During a recent hunting season, six local camps shot 19 bears and 17 bucks. Adams reported the average lactation rate (does nursing fawns) for does that were at least 2 1/2 years old from 2002-2011 was 70%. The lactation rate dropped to 25% during 2012 and 2013, and the quality of the habitat remains good.
The fawn recruitment rate on the farm used to be 1 1/2 fawns per 2 does, according to Adams. That has dropped to 1 fawn per 2 does. He added that 30 does on the farm used to produce 22 to 23 fawns. The same number of does now produces 18 fawns because predators are killing so many.
While black bears typically eat more fawns, they are capable of preying on adult deer. During DeBruyn’s study in the UP, he observed a habituated bruin and her yearlings feeding on the carcass of a deer. It was following a severe winter, and DeBruyn suspects the deer was in a weakened condition – which enabled the bears to catch and kill it.
During the first phase of the fawn survival study under way in upper Michigan, researchers also documented the predation of a healthy radio-collared doe by a bear. When the doe’s collar went into mortality mode, Nate Svobota and Heather Stricker went to investigate. They found the doe’s carcass in thick lowland habitat comprised primarily of tag alders. All of the small trees within a 33-foot radius had been broken, indicating a major struggle took place.
Nate said the doe’s carcass was partially covered with sticks and grass, which is behavior typical of black bears when they cache food for a later meal. There was a bear den 10 feet from the deer carcass.
According to Svobota, the bear didn’t eat much of the deer before caching it. The body cavity had been opened and the rumen or stomach had been eaten. The carcass contained puncture wounds and claw marks.
“The deer probably caught the bear by surprise when it was in its den or preparing the den,” Svobota said. “There was a deer trail 40 to 50 meters from the den. The deer probably came walking along without knowing the bear was there and got too close. As an opportunistic predator, the bear took advantage of the opportunity it was presented with.”
While bears alone aren’t responsible for the dramatic increase in whitetail predation in recent years, they seem to fly under the radar when the problem is discussed. Coyotes are a major contributor, but we can’t focus on one predator if we’re going to understand this new dynamic in deer management.
Editor’s note: The author has written a number of books about deer hunting as well as a comprehensive book about black bear hunting. He also produced a DVD about field-judging black bears. For more information, go to richardpsmith.com.
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