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.