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Predators and prey play an ancient game of survival

January 28, 2012
By GARRY BRANDENBURG , Times-Republican

WINTER seems to be much more enjoyable because of the wildlife we see. It can be a chance encounter of being in the right place at the right time or the alternative of using an active feeding station to draw birds of many species close to a favorite window of your home.

Both situations came about for this scribe this past week. My chance encounter involved eleven wild turkeys standing on the river snow covered ice downstream from Stanley Mill Bridge. My binoculars were a great aid in picking out the turkeys in the snowy tree snags and branches along the shoreline. Then the chance encounter happened ... when I spied a mature bald eagle cruising along the river going from north to south. He was headed in the direction of the turkeys. I speculated that perhaps the turkeys would break for deep cover as the eagle neared. Not so. Evidently the eagle was not hungry and the wild turkeys didn't panic at all. In fact they didn't move a bit. The eagle skimmed over the tree tops without showing any interest in a potential free lunch. I'm sure the turkeys were carefully watching the eagle. Eagle eyes probably did not miss the turkeys either.

The relationship between predator and prey is an on-going struggle of nature all the time. Prey species will loose some critters to the claws, or teeth of predators. Rabbit or squirrel will become a meal for the fox, coyote, owl or hawk. Prey species give life to the predator. Predators may be fewer in number but they too have their own gauntlet of things to overcome if survival is to be achieved. It is always an interesting concept to note how nature works. Humans however must be careful to not label them as winners or losers. Nature doesn't keep score in that manner. Abundant prey will always have predators but they will be proportionally much smaller in numbers.

Article Photos

A female cardinal works her bill over the outer shell of a sunflower seed. Finding food when the ground is covered with deep snow is entirely different than scrounging on the bare open land during the first half of our winter. Cardinals have a distinctive crest of feathers behind their head. Their bill is cone shaped and red in color, except for juvenile birds that have a black bill. Both females and males ‘sing’ all year long. As year round residents of the eastern two-thirds of the USA, the bright red male cardinal is easily noted, especially if it is sitting on snow covered branches of a deciduous tree.

Humans are part of the ecosystem. We are predators. We cultivate land to grow food. We manage livestock for food. Whether we hunt for our wild food or raise domesticated livestock to sustain us, we are still predators. Wildlife biologists manage those critters that are part of the wild biota coexisting with us on the land. If one looks back at America before settlement, one will note quickly that Native American Indians affected the ecosystem for at least 10,000 years. Iroquois used controlled burns to clear vegetation because they knew wildlife numbers would increase when the burned land sprouted new growth. The Cheyenne and other tribal nations hunted bison and one method was to calculate the right time to stampede the herd to run over a steep cliff, a bison jump site, where many animals died or were too injured to escape. Bison became the 'grocery store' each fall in order to put up enough stores of meat to last a long prairie winter. Other tribes farmed the land to grow crops. Others dug bear traps, used snares and other means to catch food that did affect wildlife populations. Deer skins had value and could be exchanged with the whites for trade goods. This supply/demand system worked too well and caused many wildlife populations to plummet.

In today's modern world scientific wildlife management principles can be applied to keep populations on a more even keel. Each hunting season sees limits for game, dates of effective takings, licensing requirements and other hunt restrictions put in place. Humans continue to have a big influence on all ecosystems, not all bad and not all good, but overall much better than the old market hunting free-for-all of this nation's early history. My point to remember is this: We are indeed fortunate that scientific processes are in place for wildlife management versus the old ways of take what you can where and when you can without regard to long term consequences. It is something to think about.


Iowa deer kill numbers from the current season shows almost 119,000 animals reduced from the population. Again as in past years, doe deer lead with 60,639. Bucks taken numbered 45,277. Button bucks tagged in at 12,081 and shed antlered bucks at 739. The trend line of fewer deer taken in 2011-12 from each of the previous years proves that management guidelines have met goals in many portions of Iowa. Fewer deer were taken because the population base has been systematically drawn down. I'll have more details on this in a future column.

Marshalltown's urban bow hunt for deer is currently showing 24 deer taken out. Twenty of them were doe deer, three were button bucks and one was a mature buck. The latter was taken on an incentive tag, one of only two tags issued. Twenty doe deer will result in approximately 50 to 60 less deer next year. Fawns from last spring would have had a single birth this spring. Mature doe deer would have had twins. They are not part of the equation any more. Winter aerial counts should confirm a modest decrease for the City. Depredation Biologist Bill Bunger with the DNR will have recommendations for the City later this winter as we move into the fall seasons of 2012.


CHRONIC WASTING DISEASE in whitetail deer has been confirmed in two free-ranging deer in central Missouri. CWD has also been confirmed in all the states surrounding Iowa, but not here. Iowa DNR biologists are quite aware of the potential for this disease to get here. They don't want it but it may be hard to contain. Iowa has tested our deer since the year 2000 with more than 39,000 samples taken. None of them have turned out positive for CWD. Just this past season nearly 4,500 new samples were obtained from sportsmen as part of the surveillance for the disease from every county in Iowa.

Chronic wasting disease is a brain affliction that can infect deer, moose, and elk. It is classed as a spongiform encephalopathy. An abnormal protein agent, called a prion, causes normal proteins of the brain to take on a different shape. Microscopic holes form in the brain of infected animals. It is a slow progressing disease. It does not sweep in like an epidemic. It is always fatal. It can and does remain dormant for a long time. The slow pace of CWD is what makes it seem less of a threat. In the later stages of an animal infected by CWD, the animal will appear emaciated, lethargic, and display repetitive behavioral changes. Excess thirst and salivation, tremors, and drooping heads and ears are often displayed.

Humans do not get this disease by eating venison. The affected diseased organs are things not normally eaten anyway, i.e. the brain, eyeballs, or spinal cord. The state of Illinois seems to be containing the infected area from further spreading. One of the best things anyone can do is to eliminate supplemental feeding sites where they may presently exist. Consider Iowa very fortunate at this point that chronic wasting disease is not here.


Garry Brandenburg is a graduate of Iowa State University with BS degree in Fish & Wildlife Biology. He is the retired director of the Marshall County Conservation Board. Contact him at PO Box 96, Albion, IA 50005.



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