IN NATURE’S LABORATORY

A number of features make Isle Royale an ideal place in which to study ecology. Because the island is uninhabited by humans and is protected as a national park, scientists can study moose–wolf interactions in a nearly natural environment, undisturbed by settlement, hunting, or logging.

Isle Royale is also an ideal distance from shore—close enough to the mainland for moose and wolves to have reached it, but far enough away that other animals do not migrate easily to it. Because there are no other predators or prey on the island, the only things eating moose are wolves, and moose are just about the only thing wolves eat. These simplified conditions allow scientists a good look at the two residents’ behavior and ecological impact.

Another feature that makes Isle Royale good for research is its size. The island is not so big as to have an unmanageably large population of moose, and not so small as to be unsupportive of a wolf population. “It’s a little bit of the Goldilocks thing,” says Vucetich, now a professor of ecology at Michigan Technical University. “Isle Royale is not too big and it’s not too small and it’s not too close and not too far. It’s just the right size to have a population of wolves and moose that we can study.”

Vucetich began studying wolves as a college student at Michigan Tech in the early 1990s. In 2001, he became coleader of the Isle Royale study, working alongside his former teacher and mentor, Rolf Peterson. It’s challenging work at times, but Vucetich says he may have been destined for this career path: “Vuk”—the root of his last name—“is the Croatian word for wolf.”

Ecologists study organisms at a number of levels. They can look at an individual organism, such as a single moose or wolf, studying how it fares in its surroundings. They may also look at a group of individuals of the same species living in the same place—a herd of moose, or a pack of wolves, for example—watching what happens to this population over time. Two or more interacting populations of different species constitute a community. Isle Royale, for example, is home to a community of wolves, moose, and the plants the moose feed on.

Finally, ecologists may want to understand the functioning of an entire ecosystem, all the living organisms in an area and the nonliving components of the environment with which they interact. When moose eat trees, for example, they reduce the available habitat for other animals, such as birds. However, the heat of summer can reduce the ability of moose to feed, which in turn improves tree growth (INFOGRAPHIC 21.1).

Vucetich was initially drawn to ecology as a way to experience the outdoors, his first love. Only later did he realize he was actually quite good at something ecology has a lot of: math. “As a high school student, I didn’t like math at all,” he says. But when he saw that math allowed him to spend more time outdoors he became, as he says, “interested and inspired to learn a great deal about math.”

Vucetich is a population ecologist, and population ecology is all about numbers. On Isle Royale, the main numbers the researchers are interested in year after year are the numbers of wolves and moose. “In any given season there are more or less of those species and we want to understand why,” says Vucetich. Answering the “why” involves a lot of time, patience, and, of course, counting.

Much of the counting is done from the air. Sitting one in front of the other inside a tiny two-person plane, pilot and observer circle the island scanning for evidence of wolves and moose. Wolves are relatively easy to find and count, especially in the snow: “You follow the wolf tracks until you find the wolves,” says Vucetich. The other thing that makes counting wolves easy is that they live in packs: if you find one wolf, you’ve generally found the others. And since there are usually no more than a couple dozen wolves on the island at any time, it’s possible to count every one.

It’s a different story with moose. There can be more than a thousand moose on the island—too many to count all at once. Besides, moose are relatively solitary creatures, and their brown coloring makes them harder to spot against the backdrop of dark evergreen trees. When moose are feeding in the forest—which is much of the time—counting them is, according to Vucetich, “like trying to count fleas on a dog from across the room.” It’s simply not possible to count them all.

Instead, the team uses a shortcut: they count all the moose in a series of square-kilometer plots representing about 20% of the island, average the number of moose per plot, and then extrapolate to the rest of the island. But even this shortcut requires many careful hours of study in the plane, straining to see the moose through the trees. To help himself concentrate, Vucetich recites a sort of mantra: “Think moose, think moose, look for the moose.” (INFOGRAPHIC 21.2)

The somewhat random dispersion of individually roaming moose represents one type of distribution pattern found in nature. Distribution patterns generally reflect behavioral or ecological adaptation. For moose, being solitary and randomly distributed may help protect them from predation, since single moose are harder to spot in the forest than a large group would be. A random distribution may also allow individuals to maximize their access to resources. Pine trees, for example, have air-blown seeds that are spread far and wide by gusty winds, resulting in a random distribution of trees in the forests on the island.

A truly random distribution is rare in nature; even wind-blown seeds must fall on fertile soil to grow, and this does not always happen. More common is a clustered, or clumped, distribution, which results when resources are unevenly distributed across the landscape, or when social behavior dictates grouping, as it does with the highly social wolf. Clumping has its advantages: for wolves, clumping helps them to gang up on moose; they circle their prey and close in for the kill. Clumping can also be a defense against predation, as it is for a school of fish.

A third distribution pattern found in nature is uniform distribution. In this case, individuals keep apart from one another at regular distances, usually because of some kind of territorial behavior. Birds such as penguins that nest in defined spaces a few feet away from one another are a good example (INFOGRAPHIC 21.3).