Fall 2003

By Jack MacRae

Here's what's debuting on nature's stage in Chicago Wilderness

	In September, monarch butterflies sometimes congregate before taking off from Chicago Wilderness. they will spend winter in Mexico. Photo by Phyllis Cerny.

EARLY FALL

Silk Degrees
Tiger swallowtail butterflies are non-migratory. In the fall, the second-generation caterpillars (there are two generations each summer) will construct a resilient silk chamber on the underside of a leaf. Here they will spend the winter slowly transforming into adult butterflies. Real cold.

On the other hand, monarch butterflies are migratory. They'll spend the fall flying to the Michoacan Mountains in central Mexico. Sweet!

In-Flight Meals
Fall migrations provide endless opportunities to study predator-prey relationships. The last few years, research-ers have been looking at the association between small falcons and dragonflies.

During September, large, loose clusters of dragonflies, primarily green darners, will move south along ridges and lakeshores. Simultaneously, merlins and kestrels will be in flight, perhaps following the same geographic clues. Inevitably, the two groups will meet and the feasting will begin. The falcons eat on the wing until they're full. One study found that green darners accounted for 15 percent of kestrels' diet during migration.

A few years ago, a notable cloud of tens of thousands of green darners, red- and black-mantled gliders, and meadow-hawks impressed the afternoon crowd at the Skokie Lagoons, north of Chicago. Toward dusk, the insect mass began heading southeast toward the parks and beachy spaces near the big city.

Maybe Cry Wolf
My predictions are usually wrong, but I think it is only a matter of months — not years — before we have a legitimate timber wolf sighting in the region for the first time in nearly 200 years. After all, we have a healthy population of wolves only a few hundred miles to the north, and valid reports are continually getting closer. In recent years, at least three young wolves have been found DOR (dead on road) between Madison and Milwaukee. Most notable, however, is the year-old male that traveled from central Wisconsin, through Illinois, and into Indiana, where he was hit by a car and died in an adjacent bean field. His exact route through Illinois is unknown, but it is conceivable that his journey took him through Chicago Wilderness. How cool is that!

MIDDLE FALL

Ancient Beaver Food
Imagine the impact a few 500-pound beavers would have on our riverine and wetland vegetation, especially during the fall, when, scientists believe, these prehistoric creatures ate more to prepare for winter. We know these giant rodents lived here during the cool Pleistocene — we've found their bones near the Fox River.

We also may have found some of their food. Scientists discovered two spruce logs, radio-carbon-dated back 10,860 years, near Brewster Creek as it winds through DuPage County toward the Fox River. The logs shows definite gnaw marks, although the marks seem to be similar in size to contemporary beavers, not their massive ancestors.

Living Color
The burgundy red leaves of sumac can fill the fall woods with an unmistakable hue. The fiery color comes from the pigment anthocyanin, and is greatly influenced by the weather. Here is how: Cool nights (below 45 degrees) inhibit chlorophyll production. Without chlorophyll, sugars accumulate in the leaves. Increased levels of sugar lead to a rise in anthocyanin, and the more anthocyanin in the leaf, the more color. Simple, no? Warm sun following cool nights produces the most intense colors.

We have several kinds of sumac in the region. Some are rare (fragrant sumac), some are common (smooth sumac), and some are poisonous (poison sumac). Musically, my favorite is Yma Sumac, the multi-octave singer from Ichocan, Peru, a town high in the Andes.

LATE FALL

Mud Honeys
Fall is the season for mudpuppy boys to look for mudpuppy girls for the purpose of mudpuppy love. Their relationship is brief, the father doesn't stick around, and the young mother will deposit her fertilized eggs in the spring. People rarely encounter these large aquatic salamanders, though veteran fishermen will occasionally find one wriggling on the end of their hooks. Hip herpetologists know where to find these waterdogs — in their favorite habitat, along the southern shores of Lake Michigan.

Late Bats
I once was surprised to find five little brown bats huddled in the rafters of an old Civilian Conservation Corps shelter in a west-suburban park. I wasn't surprised to find the bats there — the structure provided nice habitat — but this was almost Thanksgiving and it had been a cold week, with blowing sleet and snow. Flying insects were scarce; perhaps the bats were already living off the layer of fat they put on when the skies were warmer and buggier.

Eventually, these cute little furballs left for a warmer winter home. They didn't have to fly too far. Perhaps they went to hang out with their compadres in those spooky old mines along the Illinois River in LaSalle County. They'll dangle by their toes, in a deep sleep, until spring.