All at once five black shapes crested the bench, fluidly trotting through the elk. Wolves. We'd seen their tracks earlier that day, pressed into a skiff of snow on the Chief Mountain Highway. Few humans visited the park between late fall and spring; predators and other wildlife adapted to this by increasing their use of park roads that are closed to vehicle traffic in the off-season. Even through the blowing snow I could see that these wolves were muscular and well fed. They moved comfortably through the herd, shifting into a slow lope, tails high. The elk parted as the wolves passed, and then they regrouped a short distance away, heads up, bunched more tightly for safety. The wolves didn't stop but continued on their way, disappearing over an eskerine ridge. It was a long while before the elk settled and resumed feeding, and their vigilance level remained high for hours. Their earlier restlessness made perfect sense.
Aldo Leopold was among the first to observe the behavioral effects of lack of predation on his own land. In 1935 he bought an abandoned farm in southwesternWisconsin, to use as a hunting reserve. He subsequently dubbed the farm "the shack." This land, now known as the Leopold Memorial Reserve, lies 45 miles north of Madison, on the southern edge of Wisconsin's sand counties. The Leopold family spent every weekend there, restoring the land. Between 1939 and 1940, in his shack journals Leopold noted the effects of deer herbivory on herbaceous plants (plants whose leaves and stems die down to soil level at the end of the growing season) and trees he had planted on his land, which included oaks (Quercus spp.) and aspens (Populus tremuloides). He commented that some species were being nipped down to eighteen inches in height. In a game survey he also documented how humans had by then eliminated wolves from much of Wisconsin. Deer had exploded in northern Wisconsin, from several hundred in 1920 to at least 100,000, causing game managers to formally acknowledge the problem. Although things were not this bad at the shack, Leopold noted ongoing plant damage caused by deer, which in the absence of wolves calmly stood their ground and browsed young saplings down to nothing.
There is a saying that the more things change, the more they stay the same. And an older Romanian proverb from the Karpaten states that where wolves go around, the forest grows. Both pieces of folk wisdom came to mind when I visited the shack to see whether the current aspen growth pattern and deer behavior would fit Leopold's historical observations. It was mid-April as I drove along the rural road that runs through the Leopold Memorial Reserve, noting small herds of deer standing around with their heads down, eating shrubs. I spent the next few days examining the amount of browsing on aspen sprouts.
One day Aldo Leopold's daughter Nina Leopold Bradley joined me in the field. Her chocolate Labrador retriever, Maggie, ran glad circles around us as we examined the aspens around the shack for evidence of deer herbivory. Almost all the aspens below browse height (the height a deer can reach to eat) featured chisel-pointed ends where deer had bitten off the apical stem, the dominant growth bud. Many had zigzagging trunks, where they had been browsed and had healed, and then had grown in a different direction. I held my measuring rod to an aspen less than three feet tall and counted its browse wounds—eight in all, each marked by a crook in its trunk. I showed Nina how telltale signs on the aspen allowed us to distinguish browsing from disease, because the latter made the trees' growth tips atrophy. All aspens can sustain moderate browsing, but these bonsai aspens looked stunted and shrublike. With chronic herbivory they would eventually die. Indeed, we found many that had succumbed in this manner.
Nina and I reflected on how little things had changed at the shack since her dad's era. As we continued to walk she recalled his observations about the effect of wolf removal on deer behavior, and how deeply this awareness affected him. "My father always said it all had to do with relationships. But he couldn't convince managers of that. He was even unable to convince some of his best friends. He had found stacks of dead deer as big as a house in northern Wisconsin, and his colleagues would not vote for a doe-hunting season. I think we have the same problem today. I do not think that people, even at the highest level, quite understand the interdependence of all of these issues. We still have too many deer, we still have hunters thinking we don't have enough deer, and we still have no wolves here."