Thinking Like an Arboretum

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The annual “Thinking Like an Arboretum” tour derives from the work of three men, who live only in memory and were all important to the UW–Madison Arboretum: Aldo Leopold, Orie Loucks, and Ken Wood.

Leopold wrote an essay called “Thinking Like a Mountain,” which described the dawning of his awareness of predator-prey relationships. Prior to the events described in that story, he had regarded most predators—particularly wolves—as varmints and enemies. Eliminating them by hunting or other means was a good thing, he thought. But something about the wolf he killed one climactic day in New Mexico changed his attitude, and he began to understand how both prey and predator are necessary parts of every ecosystem, pulling it into balance and preserving its wholeness.

In 1975, Orie Loucks, then serving on the Arboretum Committee, took Leopold’s idea and refashioned it as “Thinking Like an Arboretum” (“Community Integrity in the Arboretum”), for an address delivered to the Friends of the Arboretum that year. The idea was the same: whether one is considering the soil community or any other ecosystem, each living thing plays an essential part and is vital in sustaining the health of the whole. Value judgments and personal biases have no place in such a scheme.

But Loucks did a great deal more than just write that article and give that address. He was an ecologist and scientific activist who over his long career held faculty positions at the UW, Butler University, and Miami University of Ohio. In Wisconsin in the late 1960s, he was a key scientific witness in the successful effort to get the pesticide DDT banned. He also fought Project Sanguine at Clam Lake and helped negotiate the first Great Lakes Water Quality Agreement between the United States and Canada.

Orie Loucks died this past September at age 85. I wish I had known that he’d returned to the Madison area. I would have liked to meet him and tell him that his name is mentioned every November at the Arboretum.

The final man in this trilogy was Ken Wood, a longtime Arboretum naturalist who died in 2013. It was Ken who, 30 years ago, synthesized the thoughts of Leopold and Loucks and suggested a tour called “Thinking Like an Arboretum” where we explore the roles of predator and prey. Ken’s writeup, including the full texts by both authors, still resides in our naturalists’ files.

Because the central relationship in Leopold’s essay is the one between deer and wolves, I like to use a particular Wingra Woods route for this tour. It’s one where buck rub—vivid linear scratches on tree trunks where male deer have rubbed their hardening antlers—can reliably be seen, mostly on balsam fir trees. This fresh deer sign provides a fine backdrop for discussion of the animals.

But first, we angled across a little bit of Longenecker Horticultural Gardens. I had no sooner pointed out the retained fruit on some trees in the crabapple collection and described the same as good food for our wild turkeys, than in fact we saw a sizable group of turkeys indulging! These birds were only eating the crabapples off the ground. In winter when there is snow cover, they will often fly up into the trees to get at the higher fruit. Large bird + small tree = comical sight.

Just into Wingra Woods from trail marker M3, we noted a tree on the right-hand side of the path which had a conspicuous hole about 4 ½ feet up from the ground. It had obviously been used as a bird family’s home; nesting material could still be seen in the opening. Since we had just walked past a (human-constructed) bluebird house in the Gardens, it was the perfect opening for a few words about cavity vs. free-standing nests.

About those deer. Based on evidence from wildlife cameras, we think we have 50–60 of them living in the Arboretum. It is breeding season, so there is a great deal of activity going on. Later in the winter (once romance and rivalry have cooled) and through about January, the bucks will shed their antlers. Fawns will be born in late spring and early summer; around the same time, adult deer will molt to the redder coats they wear in the warm season and the bucks will begin to grow new antlers. Late summer/early fall will find them rubbing those fresh antlers against tree trunks as described earlier. By September the molt to the heavier, grayish winter coat will be taking place. Late fall begins the rutting season all over again, and the life cycle repeats.

We don’t have wolves in the Arboretum. Our limited acreage and our position in the middle of a city won’t allow it. Wolves have re-established themselves in northern Wisconsin over the last four decades or so, to the point where we may have close to 1,000 by now. They are currently back on the federal endangered-species list, which limits what local wildlife managers can do to try and control the population. Wolves are expert killers: it’s relevant to our predator-prey discourse to know that just over half of a typical Wisconsin wolf’s diet consists of deer. Dinner on the hoof, quite literally.

Other highlights along our hike included the still-tawny tamaracks visible from the Big Spring overlook, and a yellow birch or two along the lower trail. I have always said that if I had naming rights to that tree, it would be called the GOLDEN birch, since its bark has an almost metallic sheen when touched by sunlight. The trees in the Arboretum woods are nearly all bare now, and one finds color where one can.

Our final stop, and where I read the last installment of Leopold’s essay, was at the yew collection near the Visitor Center. Yew shrubs are the favorite wintertime food of—you guessed it—white-tailed deer. If we didn’t double-fence our yew collection every winter, it would be gone by spring. One last predator-prey relationship, before we all returned to our indoor lives.

—Kathy Miner

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