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Original Issue

The Case of the Vanishing Bark

For years green firs and black bears grew up together in the vast forests of the Northwest. Then something happened that radically altered their peaceful coexistence

In the summer of 1945, a road crew, working on a Simpson Logging Co. tree farm at the southern tip of the Olympic Peninsula in Washington, reported unusual damage to a number of young fir trees. These 10- to 20-year-old Douglas firs had been completely girdled: the bark had been torn from the trees all the way around, as if with a deliberate design to destroy them. The damage was severe and thorough, unlike the random damage caused by the scraping of the antlers of a deer or an elk. In fact, tooth and claw marks indicated that it was the work of the black bear (Ursus americanus), the quaint, shrewd, timid animal that the Northwest Indians called Ichfat.

The first reports of these girdled trees aroused no great alarm. Bears, for some mysterious reason, have always been known to mark certain trees. More than a century ago John James Audubon described seeing a bear approach a tree that another bear had scraped and examine it minutely, "at the same time looking around and sniffing the air. It then," he went on, "rises on its hind legs, approaches the trunk, embraces it with the forelegs, and scratches the bark with its teeth and claws for several minutes in continuance. Its jaws clash against each other until a mass of foam runs down on both sides of the mouth. After this, it continues its rambles."

Audubon did not know what to make of this, but some later naturalists concluded that the trees singled out were measuring trees. Each bear put its teeth marks as high as possible in the bark, and, as Naturalist John Burnham put it, "the one that makes the tallest mark bosses the road."

The scarred trees remained a mystery, and one that, in the wilderness of the Olympic Peninsula, was destined to assume alarming overtones. When the Simpson road crew returned in the summer of 1946 they reported that the trees girdled the summer before had died. A careful check made for signs of new damage disclosed that the bears which were causing the trouble seemed to be moving eastward. The first damage had been found in the wild country of the Wynoochee and the Wishkoh rivers, but the depredation, on a considerably larger scale, now turned up beyond the Satsop, a river flowing southward out of the foothills of the Olympic Mountains. The same pattern of expansion continued through 1947 and 1948.

By 1950 the area was aroused. Reports of the same kind of damage to young trees were coming from all the forests of the Pacific Coast, with the heaviest damage still concentrated in the Olympic Peninsula. It reached epidemic proportions in 1950. In some plantings 90% of the young trees were destroyed.

For the lumber companies this represented a considerable loss. A big company may plant a billion trees annually—43,000 seeds per acre. At the end of five years the Douglas firs are about five feet high. When they are 35 they will be anywhere from six to 16 inches in diameter, and 70 to 90 feet tall. When they reach the age of 50, natural losses will have reduced their numbers to 250 an acre. In another 30 years, at the age of 80, they are ready to be harvested.

Now this tedious cycle was being interrupted abruptly. Bears, judging by all the signs, were undoubtedly the culprits, but it seemed impossible there could be enough of them to do so much damage. The Society of American Foresters admitted the problem of tree damage was serious, and at a meeting early in 1951 set up a committee "to determine the reasons for this excessive damage, and, if possible, what measures would best solve the problem."

In the spring of that year, an experimental control area of 8,000 acres was set up in the South Olympic Tree Farm, under the direction of Oscar Levin, then managing forester. Forestry students from the University of Washington came to live on intimate terms with every tree in the control area.

The exact cause of the wreckage soon became clear. The students found that the black bears sat quietly on the ground, wrapped their forelegs around the trunk of a small Douglas fir and chewed. Finishing one tree, they moved to another. One bear could chew as many as 40 a day. The process started about April 15, when the bears woke up from their half slumber of the winter, and continued until the middle of July or early August. Then they turned to ripening berries, which provided a tastier food.

But why did the black bears suddenly make green firs a major staple of their diet? It was well known that bears had an insatiable appetite for sweets, and that they knew the delicate cambium layer beneath the bark could be pierced to let the sweet juices ooze out. But they had never indulged their appetite for sweets on such a systematic scale before.

Two reasons were finally found for this change of diet. First of all, the bears were hungry, not just for sweets but for food. Second, in the past they had never had many young trees they could tap. In the primeval, rainy forest of the Pacific Northwest no light struck down to the undergrowth. Young trees were few and far between, occasional replacements for the forest giants. The bark of the old trees was too thick to be stripped and the seedlings were too small.

When the lumber companies' large-scale reforesting projects began, that situation changed. Large blocks of the forest were cut down and tiny seedlings planted in place of the gigantic old trees. The area came alive with blackberries, salal and grasses, which made it an ideal feeding ground for bears.

Bears came from all over and started congregating in the tree farm regions. They lived well on the berries and grasses. The bear population got bigger and bigger. In the middle '20s Ernest Thompson Seton had estimated that there were 15,000 wild bears in the Oregon and Washington national forests, or, roughly, one black bear to three square miles. In the tree farms, concentrations rose to four bears to one square mile, a population Burton Lauckhart, chief of the game department in Washington, calls "heavy" and which spells damage, always.


There was little to disturb or hinder this rapid population growth. Few bears were hunted; the bears were too smart and hunters preferred to go after deer and elk, whose hunting season was roughly the same as that of the bears.

So many bears finally accumulated on the tree farms that they reached a point where they could not survive on the available supply of their traditional diet of berries. The young trees, so laboriously planted by the lumber companies some 20 or 30 years before, were at hand. They tasted good and kept the bears from starving. It was as simple as that.

"This damage to trees is not a fad or the passing fancy of a few individual bears," said Lauckhart. "It apparently is a matter of eating forest trees or starving. There is nothing really unusual in this change in their diet. I do not believe that bears had to be taught to bark trees or that it was necessary for one bear to observe another bear feeding on trees before it would develop the habit."

As a result of the findings of the Foresters Society and the revelation that damage in the experimental area went in some places as high as 75%, the state game commission declared bears predators in the five counties that make up the Olympic Peninsula (mountain area roughly the size of New Jersey). There was no season, no license was required, and bear carcasses could be left in the woods. Elsewhere in Washington there was no limit on bears but a license was required. Oregon permitted hunting at any time, but did not class the bear as a predator.

Bear hunting emerged from the woods and became a respectable profession, a way of life for many. Bear hunters in Washington, for instance, may now get $475 per month, plus $25 for each black bear they kill.

Logging companies threw their lands open to sportsmen. Some 455 of the biggest timber owners invited hunters into about 42 million acres. Last spring officials of tree farms and individual land owners formed cooperative agreements so hunters would not merely be chasing bears out of tree farms into safe territory.


Some people, particularly Oscar Levin, who has emerged as the northwestern authority on bears and their feeding habits, felt that trapping was a better way to get rid of the bears than shooting them. The traps could be concentrated in the area where the bears were doing the damage and, unlike hunters, would not chase them out of the area to start new outbreaks.

Once the hunting started, the carnage was considerable. The bear kill in Washington alone came to 5,200 in 1957 and 6,900 last year. The growth of the bear population has been checked.

Tree damage, which started the whole thing, is no longer as critical as it was 10 years ago, but it is still costly. Since 1945 bears have killed a hundred trees in the Northwest forest for every one destroyed by fire. Bears are now used to a diet that includes young fir trees, and thinning out their numbers on the tree farms is not in itself enough. The big logging companies certainly don't want to exterminate the bears.

The final solution to the problem will come from the laboratory rather than from guns. It may be an almost absurdly simple one. The Pacific Northwest Injurious Animal Control has been working on something that will so change the flavor of sap that bears will leave trees alone.

"People don't chew two-by-fours, anyway," said a lumber official recently. "It won't make any difference to them if their lumber tastes bad 80 years from now."