The chips are down, beaver chewed chips

PHOTOS BY GARRY BRANDENBURG — Beaver chewed cottonwood tree bark and sapwood is now nothing but chips. Numerous cottonwoods adjacent to the Iowa River have been scarred by the gnawing of our largest resident rodent. When this tree eventually falls, its smaller branches will be cut by the beaver and drug into the river and the underwater entrance burrow to its bank den. Today's aerial image was made at another location, namely Minerva Creek, in 2011. The image illustrates a typical beaver dam of sticks and mud holding back stream flow waters. Deeper water creates habitat for many aquatic critters and fishes. A dam like this is temporary since the next high flow flood will wipe it away. The beaver image is of a display mount found in a museum.
Beaver (Castor canadensis), is this week’s featured creature. Last week while I was exploring natural areas adjacent to the Iowa River, I spotted at a distance several cottonwood trees with damaged bases.
It turns out the damage was caused by the teeth of beavers who had made serious attempts to fell these not so small trees. I examined the profuse pile of wood chips at the tree base, an amount not insignificant.
I am sure the beavers returned to complete their task. It will be a new site for my examination when I return.
The beaver family, most likely more than one, had created an access from the open river waters up a steep bank and through a small canyon-like trail their feet had scratched out of the river bank edge. Many travel trips up and down this trail had made the route quite evident. Once several of the nearby cottonwood trees are felled, this rodent family will have plenty of tender bark tops from manageable smaller branches to eat.
Beaver can be thought of as one of Mother Nature’s best engineers. If dam building is one of the criteria, that definition will work well. Dam building is a sure sign of a beaver family at work nearby.

The evidence is most likely a small mud and stick dam across a small to medium sized stream. Other evidence can be nearby crop field damage, or the cutting of willow and other small to medium sized waterway trees.
I have not observed a beaver dam across the Iowa River in Marshall County during my 50 plus years of river watching. Perhaps because of the river size, beavers prefer to use smaller tributary water flows.
However, as one travels upstream on the Iowa into Hardin and Franklin County, where the river becomes a smaller and smaller channel, beaver dam building attempts are possible. Local farmers will be displeased with beaver primarily if impounded waters block the outlet to field tile lines. A backhoe will be employed to dig out the dam. The pest side of beaver actions is all too common.
Beaver impoundments do create new wildlife habitat. New water and deeper water will be utilized by many fish species and birds. Local wood duck pairs may find a water filled stream an excellent close by location for their tree cavity nesting activities this spring.
Otter may explore the same waters as will muskrats. Diving birds like the Kingfisher will find its fish foods in those mini lakes.

Human county and state engineers who have had to deal with beaver dams know all too well the problems that dam plugged culverts can impose to a roadway if heavy rains and flooding runoff waters cannot safely flow through a culvert. A washed out road is a big expensive repair project. Prevention is worth the effort if a beaver dam is being built in the wrong place and discovered before a big rain event.
The history of beaver in North America is part of the reason settlers came here and began exploring new land. They were people who saw an opportunity to live, survive off the land using just their know-how and ingenuity, and make money selling beaver pelts.
Castor oil was another product of financial interest to trappers as they bartered for other things they needed. Beaver pelts are luxurious furs and did find many uses in fledgling economies.
Sadly, at the time of early explorations, what we know today about conservation management, was not available then. Trapping was unregulated and overharvest was typical. Once a stream was devoid of beaver, trappers moved into smaller streams until every beaver pocket was found and exploited.
Beavers being beavers also means that they never give up. As forest trees were cut by loggers, in time new trees grew in their place. It only takes a pair of exploring beavers a little time to find new food sources, find a tiny stream, and create a new home for themselves.
Beavers have adaptations to live an aquatic life of finding food and building dams. They have big webbed hind feet to propel themselves through water or grip muddy river banks. They have unique nose and ear valves to keep water out.
Their eyes have nictitating membranes that protect their eyes like built in goggles. A scaled tail works like a rudder when swimming. On land the tail is a support to help balance the animal. Beaver incisor teeth never stop growing. Gnawing is a must do action to have the upper teeth rasping against bottom jaw teeth to keep these “tools” effective and sharp. Sharp teeth are what they use to cut slices from a tree, leaving big piles of chips as the tree trunk gets cut thinner and thinner until the tree topples. A six inch diameter tree can be cut through in 15 minutes.
The weight of an average adult beaver is 40 to 45 pounds and may be 35 to 40 inches long. However, adult animals have been noted to reach five feet in length and weigh 90 pounds. This is because beavers are always growing their entire lives. They are primarily nocturnal and complete vegans.
They like softwoods best such as cottonwood, alder, willow, aspen and birch. They also like soybeans and corn. They do not hibernate so bark from trees is a food source they have to stockpile or cut down all winter long.
The home for beaver families locally tends to be a bank den with an underwater entrance. In Minnesota or Canadian territories, a big lodge in pond shallows is typical. Underwater entry/exits are still the norm. Inside the den above the water line will be rooms for sleeping and feeding.
Breeding may take place at age two. Kits are born in May or June, usually three or four. A family, or colony, is the adult pair, their juvenile offspring of the prior year and the new kits.
Predators of beaver are coyotes, wolves, black bears, bobcats and otters. Therefore a beaver is well aware of dangers that it must face and evade. Another predator is a human trapper who upon instructions from a landowner wants the pests removed.
We could consider backhoe machinery to be a predator to remove beaver dams. Beaver can be a real rascal with perseverance that never quits. Learning to outsmart beaver is a human engineering plan that can be made to work, but is still work with a capital W. The end result is this animal is here to stay, hopefully in natural settings where its living does not interfere with people too much.
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Welcome to February, the month of only 28 days, except every fourth year when us humanoids have to adjust our calendars for day length correction of our earth orbit time around the sun. Beginning on Feb. 1, we will have a day length of 10 hours and one minute.
On Feb. 28, day length will be 11 hours and 11 minutes, a noticeable gain that tells us winter is half over. We must be prepared for any type of future winter weather from mild to windy to snowy to blizzards and even rain.
Mother Nature stands ready to sock it to us humans who may become complacent. Be ready for anything and just adapt to the flow of natural events as they transpire.
Natural happenings in February include eagles establishing territories, ice fishing huts on public waters becoming hazardous on thinning ice, paddlefish season opens on the Missouri and Big Sioux rivers of western Iowa, Great-horned owls are on nests, cardinal birds begin singing songs of territorial stakes and mate calling, backyard bird count events take place, walleye fish netting for hatchery work will begin again for another year. Also of note: William F. Cody, also known as “Buffalo Bill Cody” was born in Iowa at LeClaire, a City along the Mississippi River.
On Feb. 10 from 11:30 to 12:30 (noon time) is a very informative and excellent program coming to the Grimes Farm and Nature Center. Africa’s Best slide show will be presented by Ty Smedes, a professional photographer who has made nine trips to Africa.
He has 300,000 images on file. Obviously he will show maybe one hundred images from various photo safari excursions, just some of his best of Africa selections.
Ty has also agreed to present a program on the same topic about Africa on Feb. 13, a Thursday evening, at the Grimes Farm for the Izaak Walton League of Marshall County’s Wild Game Supper potluck. Various dishes of wild meats will be available for sampling.
In addition there will be plenty of desserts and other foods to fit anyone’s tastes. The public is welcome to attend, for free, to hear and see what Ty observed and captured with his camera gear. This is a must see program to learn more about the big wonderful world of nature on the continent of Africa. I’ll see you there.
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For your funny bone: “You know you have pulled off something pretty well when….you are grinning like a skunk eating onions.”
Anonymous
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Garry Brandenburg is the retired director of the Marshall County Conservation Board. He is a graduate of Iowa State University with a BS degree in Fish & Wildlife Biology.
Contact him at:
P.O. Box 96
Albion, IA 50005
- PHOTOS BY GARRY BRANDENBURG — Beaver chewed cottonwood tree bark and sapwood is now nothing but chips. Numerous cottonwoods adjacent to the Iowa River have been scarred by the gnawing of our largest resident rodent. When this tree eventually falls, its smaller branches will be cut by the beaver and drug into the river and the underwater entrance burrow to its bank den. Today’s aerial image was made at another location, namely Minerva Creek, in 2011. The image illustrates a typical beaver dam of sticks and mud holding back stream flow waters. Deeper water creates habitat for many aquatic critters and fishes. A dam like this is temporary since the next high flow flood will wipe it away. The beaver image is of a display mount found in a museum.