07/28/2004
Moving Down from the North
I have no more than a handful of memories of my childhood in Denver, Colorado, where I was born and lived until the age of 5. One memory is of a trip to the mountains and feeding peanuts to the chipmunks. Ever since, I’ve thought of the chipmunk as a cute little critter. Within the past year or two the chipmunk population in our town seems to have exploded and a few have chosen our yard as their abode. In fact, we’ve been waging a battle with them over property rights to the entrances to our kitchen and our porch. If you follow the comic strip “Over the Hedge”, it’s much like the ongoing conflict between the humans and the raccoon and turtle and their animal companions.
Actually, we do have a raccoon that tips over our garbage cans. The chipmunks are tunneling under the bricks comprising our kitchen entrance. As a result, the bricks are sinking. Chipmunks like to dig their tunnel entrances in obscure places under stones. A pile of dirt keeps appearing on top of the flagstone step to our porch. We put the dirt back in the hole and the next day it’s back again. My wife thought mothballs in the hole would stop the activity but the dirt plus the mothballs end up on the flagstone.
After weeks of fighting a losing battle, I wasn’t surprised to read of the work at the University of Illinois at Urbana-Champaign that confirms the hardiness and stubbornness of the chipmunk. The university’s Web site cites the work of graduate student Kevin Rowe, working with Prof. Ken Paige and with Edward Heske and Patrick Brown of the Illinois Natural History Survey. These guys trapped 244 chipmunks, nipped off bits of tissue from the tips of their ears and released the animals at the sites of the trappings. They then analyzed DNA from the tissues.
When you think of the Ice Age in North America, you think of huge sheets of ice spreading down out of Canada driving any animals southward. As the glaciers melted back, the animals returned northward. There were many periods of glaciation and meltback over the past million years. The ebb and flow of the animals being pushed southward and then returning as the glaciers melted has been the commonly accepted scenario. My 1962 World Book Encyclopedia describes such a pattern.
Now it seems that at least one animal was an exception. The Illinois researchers were surprised to find that the DNA samples show that the chipmunks now living in Wisconsin and Illinois have ancestors who survived the last North American ice age. These sturdy contrarians stayed up north, then came down and mixed in with other groups of chipmunks coming from the warmer southern and eastern climes.
The researchers’ findings indicate that during the ice ages there were patches of land, “refugia”, that were not covered with ice but were forests with enough plant life to sustain our hardy chipmunks. Apparently, there is now some geological evidence that supports this conclusion. According to Prof. Paige, their study shows that it will not be as straightforward as thought previously to predict the movements of various animals during the global climate changes now underway.
Back in Denver some years ago, my wife and I took a side trip to Yellowstone and to Jackson Hole. We stayed in a cabin at Jackson Hole Lodge for a couple of nights and I may have written earlier of our experience with another small rodent. The first night, we were awakened by a mouse nibbling on my wife’s purse and spent most of the night chasing it. The mouse kept returning to the purse. The next morning I went to the Lodge desk and asked if they had a mousetrap. Yes, they would loan me a trap. However, they warned that, if I killed the mouse, I would have violated park, maybe even Federal rules against harming a wild animal in a national park.
Fortunately, I found the hole that the mouse used to gain entrance to our cabin and plugged it with aluminum foil. It worked and I didn’t have to worry about being jailed for killing a mouse! The incident brought home to me the complexity of trying to save our environment. On that same trip, we saw in Yellowstone the beginnings of recovery of areas that had been burned out during a period of severe wildfires. These fires, you may recall, stimulated much discussion and controversy about when we should intervene to stop such fires and about the possible benefits of controlled burns and logging. The controversy still continues, with defenders and critics of the Bush administration’s policies in this area.
Among the casualties of the Yellowstone fires were aspen trees, whose yellowed leaves in the fall provide a glorious golden hue to Western vistas. But aspens, cottonwoods and other trees have also been in trouble in Yellowstone in areas unaffected by fire such as the Lamar Valley. The problem is not that there aren’t aspens and cottonwoods around. There are but they are old, maybe 70-100 years old. Until very recently, however, there were no young trees to replace the geriatric trees. What was the problem and what was the solution? That’s the subject of “Lessons from the Wolf”, an article by Jim Robbins in the June 2004 issue of Scientific American.
Photos from the early 1900s show a Lamar Valley loaded with young aspen and willow trees. By the 1930s, there were virtually no young trees in the valley. William Ripple of Oregon State University was intrigued and began taking cores from the trees. He found that none of the sampled trees grew from the 1930s to the 1990s. Only two of the trees sampled had started to grow after the 1920s. Ripple realized that the 1920s were when the last of the gray wolves in Yellowstone had been killed or driven out.
With the wolves gone, the elk needed no longer fear being eaten and they came forth and multiplied, gulping down every young tree that emerged from the ground. Hordes of elk stripped the valley of vegetation. Beavers no longer had food and they departed in the 1950s. Without the beaver ponds to encourage the growth of succulent plants, grizzlies could no linger rely on the succulents that furnished them sustenance when they came out of hibernation. What to do? Bring back the wolves!
In 1995, the experiment began. Where to get the wolves? There were wolves in neighboring Montana but these wolves were used to preying on deer. In Canada, there were wolves that preyed on elk. A group of 14 wolves was brought in from Canada in 1995 and another 17 in 1996. To avoid genetic problems from inbreeding, the wolves were taken from different packs in Canada. To keep the wolves from becoming used to humans, they were kept away from human contact in 1-acre holding pens for two months before being released. As of the end of last year, the wolves had formed 16 packs with a total of 170 wolves. (An article by John Pickrell dated December 4, 2003 on the National Geographic Web site gives figures of 21 packs and 220 wolves in Yellowstone and the surrounding areas at the end of 2001.)
Whatever the wolf numbers, the elk population has dropped significantly and the remaining elk have become smarter. They have decided that grazing in river bottoms and places where they don’t have a panoramic view of their surroundings makes them prime targets. They have wisely opted to move to places where they can command better views of their surroundings and any predators. Young trees are thriving in areas that have been vacated by the elk. Beaver have returned and started building their dams. The trees also help stem erosion and the woody debris pools in the river, promoting slower flow and trout habitat.
The wolves also typically leave the elk carcasses before fully consuming them, thus providing food for scavengers such as coyotes, ravens, grizzlies, eagles, magpies and the like. Songbirds are back. Obviously, the wolf has done its job well. Or has it? A recurring theme in these columns is that there are always skeptics and this case is no exception. Skeptics point out that there hasn’t been a truly harsh winter since the wolves were introduced, that the climate has been warmer and that there has been flooding along the river. It may take years for the wolf’s full effect to be determined but, in the meantime, I’ll consider the experiment a big success.
Interestingly, just a couple weeks ago, Gail Norton, Secretary of the Interior, proposed to remove the gray wolf from the endangered list from Maine to the Dakotas. In an AP dispatch on AOL News Steve Karnowski reports that the new regulation would, however, maintain the “threatened” status for the gray wolf across the West, including Yellowstone.
As for me, what to do about those pesky chipmunks?
Allen F. Bortrum
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