A Bearing on Bears

"Tick . . .tick . . . tick . . . " intones the radio receiver. The sound carries distinctly in the chill New England air; the electro-magnetic pulse the only indication that a radio-collared bear lies concealed in a den somewhere in the snow ahead. The group of about 20 college students listens and waits in the forest while wildlife biologist John McDonald snowshoes ahead with a few rifle-toting assistants.

While the students stand and shiver in the woods, Todd Fuller, Director of Natural Resource Studies at the University of Massachusetts, lectures them on Ursus americanus, the black bear. The students - future biologists here for a session on outdoor field techniques - eagerly jot down notes.

Fuller stresses the importance of the radio collar. Without it, a hibernating bear would be virtually impossible to locate. The collar also has an added benefit of sounding a warning. "If she takes off and comes at us, the signal will get louder," Fuller says.

Fuller adds that McDonald, a Ph.D. candidate in wildlife biology, has the most dangerous and difficult job: "Imagine trying to sneak up on the bear in this snow, almost waist deep, and then jab her in the butt with a tranquilizer dart!"

After a long wait in the cold, the students are rewarded for their patience; McDonald has successfully extracted a female black bear from its den of logs and brush. After struggling uphill to the site, the students find an unexpected surprise in the form of a pair of weeks-old bear cubs. Too young to open their eyes yet, these fraternal twins begin to squeal when temporarily removed from their mother's body heat for a physical exam.

One of McDonald's assistants, Joan Milan, stuffs a kitten-sized cub inside her winter coat to keep it warm. The cub quiets instantly and clings to her sweater, crying out only when Milan tries to remove it. Everyone clusters around and wants to hold the other cub; it is easy to see why researchers call bears "charismatic megavertebrates."

Like the biology students on this field trip, humanity in general has long been fascinated by bears. There is archaeological evidence of bear skulls used in religious ceremonies by Neanderthal man. Early explorers of the North American continent reported that some Native Americans lived in dread of the bear's reputed supernatural powers.

McDonald admits that part of the appeal of studying bears is this very mysteriousness. A large man in his late twenties, bear-like himself in appearance, he becomes animated when talking about his favorite subject, and uses souvenirs from his fieldwork to illustrate his points. "They're secretive, curious animals," he said during a recent interview, "the ones that generate the most excitement, folktale and myth. Like most big animals," he adds, "there's more of them out there than most people think."

There are more bears than ever in western Massachusetts, reflecting a phenomenal growth rate of 8 to 10 percent per year in the bear population. Todd Fuller estimates that there were about 10 bears in the entire state in the 1940s. Now Massachusetts can claim "somewhere between 975 and 1175 bears," according to Jim Cardoza, a state wildlife biologist and bear project leader with the Division of Fisheries & Wildlife. The bulk of the population is located in rural areas west of the Connecticut River, but there are probably 50 to 100 bears well into the outermost suburbs of Boston.

McDonald hopes to use his data project future bear populations by figuring out the relationship between the amount of available food, the mother bear's resulting body weight, and the number of cubs that grow into adulthood. McDonald thinks the major reason for the bear population increase lies in the humble acorn, and hopes this knowledge can be used to predict bear numbers and behavior. "Acorns are really high in fat and a good energy source for bears," he explained. "They can gain a couple of pounds a day in a good mast (acorn) year, like this year." By way of example, he cites the documented case of a bear in Minnesota that gained 250 pounds in two months from such a diet.

The significance of this, he said, is that the heavier the female bear, the more likely she is to successfully give birth. Knowing this fact carries many implications; McDonald noted "It's expensive to follow bears around and put radio collars on them. So if we can go out and count acorns and predict from that what the reproduction's going to be, it's going to be a lot cheaper for the state."

Besides predicting the number of bears, acorn counts can be used to predict bear behavior. When the acorn crop is good, bears remain in the woods. When the acorns crop is poor, however, bears start foraging outside the forest, invading corn-fields, beehives, gardens, and backyards in their frantic search for food to carry them through the winter. Sometimes these foraging bears will scare people in their homes. "There's one in Ashfield that came into someone's house a couple of times," McDonald commented.

When incidents like that occur, more people start demanding that bears be removed. Todd Fuller, McDonald's doctoral adviser, declared the results of this study "crucial, in the sense that we can determine if there are too many bears, or it's just a strange year in terms of food supplies in the woods."

McDonald gave more details during interviews at his 200 year-old home in the rural town of Goshen. Crammed with zoology texts and reports, the space reflects the interests of McDonald and his wife Jennifer, a forester. The bookshelves harbor a collection of miscellaneous bear skulls, rabbit feet and squirrel tails, as well as a fantail of grouse feathers. A nearby table is like- wise covered with walkie-talkies, receivers, radio collars, and vials of animal tranquilizers.

While McDonald talked in front of the living-room woodstove, the family dog, Sassafras, sat on a tall snowbank outside the house and peered in through the plateglass window. This golden retriever has experience with bears as well - she treed a bear in the front yard two winters ago.

The dynamics of bear populations can be thought of as a game of energy, McDonald said. Getting plenty of food is key. A female bear, or sow, has a taxing job. "She's got to store half a year's worth of energy in less than half a year's worth of eating," said McDonald. After mating, a sow has only a few months in the late summer and fall to store enough body fat to meet the energy needs of three bears - herself and two newborns - through-out the winter. Just giving birth in the coldest season of the year is a tremendous energy burden, not to mention nursing her young until the first berries ripen in the late spring.

And all this energy-draining activity occurs during the period of semi-wakefulness known as hibernation, when a bear does not eat, urinate, or defecate. By the time winter is over, the bears "are pretty well tapped out," commented McDonald.

However, sows have a few tricks up their furry sleeves to even up the score. One important, little-understood aspect of bear physiology is a thing called 'delayed implantation.' After a sow breeds in July, the fertilized egg develops to a few hundred cells and then stops. All summer and fall it floats free in the uterus, drifting in a state of suspended animation. It doesn't implant and resume growth until early December. As a result, the sow is truly pregnant for only about six weeks before giving birth in January.

McDonald said that researchers hypothesize that one advantage of delayed implantation to the sow is that "Her body can tell, based on how fat it is, if she's going to have enough energy to support her and her cubs until she comes out of the den." If the sow reaches the threshold weight that will allow her to carry and nurse her young, the embryonic cells will implant and begin normal growth; if not, the embryonic cells will be resorbed, and the sow will not be burdened with the energy demands of pregnancy and nursing. No one yet understands exactly how the delayed implantation process works, but McDonald thinks that there's some hormonal signals playing a role.

Scientists also suspect that delayed implantation may enable a sow to hold fertilized eggs from several different males at the same time; allowing her, in a sense, to bank fertilized eggs for the future. If true, this would guarantee the sow a pregnancy, an important consideration to a mammal that normally comes into heat only once every two years. One curious result is that sibling cubs have the same mother, but may possibly have different fathers.

Besides delayed implantation, the sow's most important survival strategy is to expend as little energy as possible while storing up as much energy as she can. Bears are opportunists, typically feeding on whatever resource is most readily available, in the greatest quantity, and requiring the least amount of effort to obtain. This is why bears, omnivores like ourselves, tend to consume much greater quantities of plants, fruits and nuts than they do meat. As McDonald points out, "It costs a lot more energetically to chase down a healthy deer than it costs to chase acorns."

Likewise, bears prefer to stay in one spot and stuff themselves. If given the chance, an average bear will eat 20,000 calories in one day; ten times what the same-sized human consumes. When a bear invades a cornfield or a blueberry patch, it may gorge itself until quite literally sick. Sometimes these foods ferment in their stomachs and cause them to regurgitate, leaving what looks like a bucketful of corn or blueberries that someone has dumped upon the ground. Their preferred food is acorns however. McDonald remarked, "If there's a lot of acorns they'll eat all day and they'll eat all night."

One possible reason there are more acorns available for bears to eat is due to a change in the landscape. Hike in the deepest woods here, and old stone walls and cellar holes pop up, the remnants of farms from a century or more ago. At that time, much of the land was scalped bare of trees so that crops could be planted. Historians note that Massachusetts was largely cleared of its forests by the mid- nineteenth century. With this loss of habitat, woodland animals began to fade away.

"Bears didn't disappear, but they came darn close to it," said state wildlife biologist Jim Cardoza, who made some of the initial studies of black bears in Massachusetts during the early 1970s. "They needed forests to sustain themselves, and there weren't any forests. We probably lost our resident population some- time between the Civil War and the 1880s when all we had were wandering males that came in from the north of us."

This situation changed as farmers moved west and New England agriculture declined. Fields were abandoned, leaving only mute stone walls behind. Trees slowly colonized this available ecological niche, arriving in successive waves of pioneering sumacs, birches, conifers, and finally, sugar maples and oaks.

This transformation took many generations, but on a recent hike I was able to stand in the stony remains of an old farmhouse and look up at a huge red oak sprouting out of what had once been a chimney foundation. Wrapping my arms around the tree trunk, I found my fingertips would not meet.

Such mature trees are once again dominating the landscape, and the oaks within them are prolific acorn producers. As a result, one unanticipated effect of the decline of agriculture has been the development of forests that provide plenty of food and cover for large mammals.

"A lot of people don't realize that there are things like bears and moose and fisher in the state," commented Cardoza. "They think Massachusetts is basically Boston and Cape Cod."

McDonald said this heavily forested landscape is comparable to western Pennsylvania, home of the largest black bears in the East, and not coincidentally the place where he was raised. (He first developed his interest in bears while hunting in the countryside west of Wilkes-Barre.)

In the years since he first took an interest in bears, McDonald has found that the hardest part of his fieldwork is learning how to immobilize a bear properly, McDonald observed. A dart full of an immobilizing drug is placed on the end of a long wooden pole, and then injected into the bear. "The first time I did that was quite an experience," McDonald said. "The bear was in a big bulldozed pile of roots, next to where somebody had built a house. You're poking around in all these holes and looking for the bear, and you know she's in there, but you don't know what hole she's going to be coming out of."

He learned that there's one crucial step: after injecting the drug, be sure to wait 10 to 12 minutes. "Then you grab them by the back of the head and shake them to see if they're awake or not."

Further guidance on the craft of bear handling was provided by 79 year-old Ethan Howard, described as an instructor in woodcraft. Howard claims to have been in the woods all of his life; he's worked for the University of Massachusetts at Amherst since 1949, and still teaches the mysteries of tracking, snaring, telemetry and denwork. "I have a lot of respect for bears," he said. "All of them are dangerous to some degree. If you know what you're doing, you don't have a problem. I don't, anyway," he added.

The techniques of field research have changed dramatically since the time Howard started. In the days before radio collars and global positioning systems, research was more or less a visual count, and a good deal of wildlife biology meant looking for tracks in the snow. The work done now is much more sophisticated, involving people from several disciplines - some of them out of the ordinary. (See accompanying article, Not So Gummy Bears.)

On the last few bear trips, McDonald and his team of helpers (including Howard's son) have attached radio collars, and then drawn blood and milk samples. Occasionally, a local dentist, John Grippo, takes dental impressions for a study he's doing on bear teeth. McDonald told of someone who once went so far as to do a spectrographic analysis of a hibernating sow.

Their findings? "The nipples are the warmest part. The cubs go right to them."

The final part of our particular expedition involves weighing the bears. After this step, the team will carefully put the sow back in her den, on top of a dry bed of freshly-placed evergreen boughs. Her cubs will be returned to her just before the den is sealed up again.

Weighing the cubs is easy - they're simply placed in a wool cap hanging on the end of a scale. Weighing their mother is more difficult, however, and several men are necessary to hoist her into place. In the process, I brush her paw; it feels hard and leathery. It is amazing to think that a bear's claws have touched me; this is the closest I have ever come to a bear in the wild - or care to. It is closer by far than some sightings of grizzlies made during camping trips in Yellowstone National Park.

Everyone takes a guess as to the bear's weight; surprisingly, she weights only 155 pounds, one of the smallest sows studied. Later, McDonald comments that bears always look bigger to the public than they really are.

"No one's ever seen a bear smaller than 300 pounds," he confides, "and the biggest ones we've ever tagged are 300 pounds. Everybody sees them but us."

Massachusetts Wildlife Magazine

----------------------------

Not So Gummy Bears

Do humans brush their teeth too hard? A dentist in western Massachusetts, John Grippo, hopes to find out - by studying bear teeth.

For years, dentists have noticed that longitudinal grooves are showing up more frequently on people's inside lower teeth, usually near the gum line. Most have blamed this on overly vigorous brushing, but Grippo suspects other factors, such as an aging population and the increased consumption of more acidic foods. Grippo is especially interested in the role of fruit juice; he theorizes that the acids contained in fruit may help eat away the dentin of the teeth.

"What I'm trying to do is basically say that tooth-brushing isn't the whole story," said Grippo. "What we're trying to introduce is the concept of stress corrosion."

Grippo explained: "When you have a liquid that's acidic, like orange juice, that flows over the tooth, the movement is erosive and the acid activity is corrosive." These two processes are most effective near the gum line, a weak spot especially vulnerable to acidic activity. Teeth there are already under a lot of stress, and subject to constant bending and flexing, a process that Grippo likens to "pulling on a bow and arrow."

To prove his idea, Grippo started looking at bear teeth. A bear's diet is much like a human's, he says: both eat similar combinations of meat, fruit and vegetables. Bears also consume a lot of acidic foods, such as berries and acorns. Since bears obviously never brush, any grooves found in their teeth would have to be caused by something other than tooth-brushing.

So, for the past two winters, this 66-year-old dentist has snowshoed along with wildlife biologists on their forays into bear dens.

After the hibernating bear has been immobilized with a drug injection, Grippo VERY carefully reaches in the bear's mouth with a mold and makes an impression of its teeth. He has to be cautious, even though the bear is tranquilized and has a gag in its mouth. "It could spit it out and take your hand off," he commented. "Their molars and incisors are huge."

There are other problems for Grippo as well, such as getting himself hung up on barbed wire while trekking out to the den. Or having his dental materials freeze. Luckily, there is no lack of bears, and John McDonald, head of the bear research team, welcomes having Grippo come along.

As to the results of the bear tooth study, Grippo said, "I was amazed at how worn their teeth were." Even the teeth of young bears, under three years old, showed wear. Grippo has studied two bears so far, and hopes to study ten more.

Grippo admits that there may be other factors involved in the creation of grooves in teeth. To round out his studies, he plans to examine the teeth of other species, and to look at their diets. So far, he has looked at the teeth of cats, deer, whales and bears; he plans on looking at chimps next. Hess confident of his findings, and has co-authored an article on tooth corrosion to be published this year in the Journal of the American Dental Association.

What's the most striking difference between the teeth of humans and those of bears?

"You might say we don't have big fangs," said Grippo.

Massachusetts Wildlife Magazine

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