The Lekwa family has more than usual to be thankful for as we approach Thanksgiving this year. There is, of course, my pretty complete recovery from last year’s battle with cancer. We have even more to be thankful for now. Our daughter and her family lived in Washington, Ill. Their home was damaged beyond repair in the Nov. 17 tornado that literally destroyed a large part of their community. They survived the storm huddled in their basement bathroom tub and were completely unhurt. The walls and part of the roof are still standing, so some of their things will be salvageable, but some of their neighbors will be able to salvage little or nothing. They are staying with our son-in-law’s parents in a neighboring community for the time being.
Several folks have asked me about increased beaver activity in the past few days. I’m not surprised. Most of the past 20+ years have seen above average precipitation that resulted in consistently high stream flows. Resident beavers didn’t need to bother with dams to keep water at comfortable depths for their underwater bank den entrances. Their feeding could be more spread out, too. Droughts tend to concentrate beaver activity, though. They build dams to hold back enough water to keep their den entrances safely under water when stream flows diminish and may be driven out of smaller streams that go completely dry.
Beavers are a normal and important part of riparian forest ecology. They cut trees near the water as building material, but also to get at the tender bark in the higher, smaller branches. Thin, tender bark and the thin living layer of tissue between the corky outer bark and the heart wood of the tree’s trunk are primary foods for beavers. They supplement that with other greens in season and, especially in Iowa, corn. The trees they cut tend to sprout back rapidly from the still-living stumps and roots. Those bushy, fast growing sprouts become an important food source for deer. Beaver’s pond-building activity provides some of the only places where a wide range of fish and aquatic wildlife find refuge to survive drought periods.
There are, of course, times when beavers cause problems, too. People love living near water and really get upset when local beavers decide that their ornamental trees are a buffet set out just for them. Beavers don’t like getting very far from water, but will go several hundred feet to get to favored trees if they’re hungry and have to limit their feeding to areas around their isolated pools when it’s dry. They can also back up drainage tile when their ponds get too deep. I can’t remember how many times I had to clear miniature dams from the spillway pipe at McFarland Lake. Sometimes the beavers would have them rebuilt by the next day. They had a bad habit of eating new young trees we had planted in the park, too.
We even trapped a few of the beavers, but more always moved in fairly soon. An adult pair of beavers usually has three to four young, known as kits, each year. The young stay with the parent colony until their second fall, when they disperse and establish colonies of their own. Beavers have few natural enemies any more. They are mostly nocturnal and seldom seen, but are established in just about all the available habitat in Iowa.
Prized trees near streams and ponds may need to be loosely wrapped with chicken wire three feet high to discourage beaver damage. The wire needs to be loosened periodically to keep it from becoming too tight as the tree grows. Smaller trees can be protected with various forms of tree-wrapping material or by placing a piece of plastic drainage tile over them. Repellant sprays may be effective for a short time, but need to be replaced every few weeks or after heavy rains.
(Steve Lekwa is the former director of Story County Conservation.)