Predator Impacts On Wisconsin Deer

[Fitter]

Scientists with the Department of Natural Resources and the University of Wisconsin will launch an ambitious, multi-year field research effort to better understand the impacts predators such as wolves, bears, coyotes and bobcats have on white-tailed deer in Wisconsin.

A review of existing literature on predation and a mathematical analysis using Wisconsin’s extensive harvest and population data suggest a low level impact, but just how much, at what times, by what predators and under what conditions are all relatively unknown at this time, scientists said.

“The literature review and data analysis are first steps that identified the need for specific field research on deer predation and how that research might be designed,” said DNR research scientist, Christopher Jacques.

A particular concern being raised by hunters is the fact of expanding wolf and bear populations in Wisconsin. Both are large predators that feed on deer either primarily as in the case of wolves or occasionally as in the case of bears.

Some hunters argue an expanded wolf population, in particular, has resulted in fewer deer in the northern and central forests.

Review of published research and preliminary data analysis suggests bears are having a small but measurable impact on fawn mortality and that wolves have a small impact on the mortality rate of adult does.

One study in northern Wisconsin will use radio telemetry to track fawns and determine how many are killed by predators and by which predators. Almost nothing is known, for example, about the impact of coyote and bobcat predation on deer in Wisconsin. Similar research is underway in Michigan’s Upper Peninsula, and the two states are sharing results.

Another study, set to run for five years, will use a combination of field research methods, including radio telemetry, to study buck mortality. This research, on the DNR wish list for more than a decade, was recommended by independent auditors in 2006 to fine tune Wisconsin’s procedures for estimating herd size.

The review of published research on predation and the early analysis of Wisconsin data were done by researchers Jacques of the DNR Bureau of Science Services and Tim Van Deelen of the University of Wisconsin- Madison. They unearthed 90 studies from the U.S. and Canada, most conducted in recent years with a few dating back to the 1960s and 1970s. Their complete review is available on the Wisconsin wildlife survey page of the DNR Web site (look under deer).

Many deer hunters tend to believe that every deer killed by a predator results in one less deer available for a human hunter to harvest. Research has found the truth to be more complicated. Predators do not, in fact, always reduce the population growth rates of prey.

Biologists use the terms “compensatory” and “additive” to describe the impact of predation on any given wildlife population. If predation is “compensatory,” it means the total number of prey to die in any given year does not change as a result of predation. It means the predators remove the number of animals that would have been lost anyway to other causes.

If predation is “additive,” then the predator is killing prey animals that otherwise would have survived the cycle of seasons. In these cases, the predator is slowing the growth of the prey population, or in some instances, causing that population to decline.

Not surprisingly, the truth in any given predator-prey system often lies somewhere between with some predation being compensatory and some being additive. The trick is to determine degree. If predation has an “additive,” or negative, effect on prey population growth, is the effect small or large?

Jacques and Van Deelen applied statistical analysis to ten years of field and registration data (1998-2008) supplied by hunters from 57 deer management units, or DMUs, in the northern and central forests.

This 10 year period coincides with a steady increase in wolf populations and a probable increase in bear populations in the northern and central forests.

The Wisconsin researchers were looking for relationships, or correlations, within this large mass of data. For instance, do the data show a relationship between increasing wolf numbers in a given area and the growth rate of the deer herd? If such a relationship is revealed, researchers call this a “signal.” The signal can be positive or negative, weak or strong.

This statistical analysis does not show cause and effect, Van Deelen cautions. Nevertheless, the numerical “signals” it produces are valuable markers, pointing to areas where further research is needed to explain the numbers.

The statistical model created by Jacques and Van Deelen suggests black bear presence is associated with a reduced population growth rate for deer of less than one percent. Under this model deer herds would still grow in the presence of a large bear population, just at a slightly reduced rate. The model also suggests that the presence of wolves is related to a slightly increased rate of doe mortality.

“This early analysis appears to say that impacts on deer populations associated with bears and wolves are clearly minor relative to impacts associated with hunting by humans,” said Van Deelen.

These statistical relationships reflect what could be happening across large regions according to biologists. The numbers have nothing to say when it comes to an individual hunter and the 40 or 80 acres he or she hunts.

“If you happen to be hunting in an area of wolf activity,” Jacques said, “it could affect deer behavior or movement patterns and the number of deer you see.”

DNR wildlife officials are committed to continually improving the quality of the state’s deer management program. Hunters play a critical role in this process, and as the agency moves forward with its ambitious research program, hunter involvement will be more important than ever.

FOR MORE INFORMATION CONTACT: Keith Warnke, DNR big game ecologist, (608) 264-6023 or Bob Manwell, DNR communications, (608) 264-9248

I went to a DNR meeting on the deer hunting situation, and naturally the discussion came around to this point on a couple of occasions. The DNR did some sidestepping and circumspect commenting on the issue, but they feel that it is not a major contributor to reduced numbers of deer seen this fall. As you might guess it was not a real popular stance!

However, I have to agree with the comments they were making, and can probably shed some light on the attitudes expressed by the hunters at the meeting.

The DNR states that their study shows the wolf kills are "complimentary" rather than "additive", if the deer densities remain above 10 per sq mile. They define that as the deer killed by wolves do not overall greatly affect the annual population numbers from year-to-year, unless the densities are down too low - then they will decline precipitously. What this means to hunters is that wolves compete with us for available deer, but don't reduce year-to-year numbers. If there are 20 deer in March, they will have about 15 offspring, resulting in 35. Some will die from Weather, PREDATION, Car kills, and other problems before they ever get to deer hunting season. If there are no wolves around, the only predation window of opportunity is during the fawning stage. If there are wolves around - it is year-round hunting season on deer (yes, even adult bucks). If the 35 deer see "normal" mortality (without wolves) there will probably be between 30 and 25 deer at the beginning of the season - if the "overwinter goal" is 20, then the DNR will issue tags accordingly to reduce nubmers to 20. If there are wolves around, the September population density might be only 22. If the DNR is on top of things, they can only issue 2 permits per square mile, however they likely won't be that closely tuned, so they will still issue approximately 10. If we only see about 2 dumb deer walking around in broad daylight, then the overwinter number is still 20 and the wolves have been a "complimentary" predator. If we get lucky and we shoot 6, then there are still 4 whiners out there crying that the DNR can't count deer, and the overwinter population is 16.

This is not necessarily a bad thing, because deer are resiliant, and the carrying capacity of the land sets the birth rate. The next spring IF the weather is good and the food is plenty, the fawning season will probalby provide a crop of 20 or 25 fawns, instead of last year's 15. This bouncing ball will continue to work out the inaccuracies for decades until something happens. It is possible that a drought could drop populations precipitously - requiring a cancellation of deer hunting season to avoid dropping below the point where the wolves become "additive". If we decide to hunt anyway, we are the "additive" preditors. It is also possible that the wolve population explodes faster than the deer can rebound, and the wolves over predate the population. This would most likely happen if the hunters don't do thier job and the deer population explodes (more food = more puppies). It is also possible to happen (since wolves live to be in their teens), if the tree huggers don't let us hunt the wolves and they have good habitat and plenty of prey (as central/northern WI offers). I don't know if we are there, yet, as I don't spend much time "up north", but I suspect it may be on the horizon from the stories I hear from my friends that do.

Of course, we would all love to be able to say "The DNR knows best and if they say it is not a problem, then it isn't." I have to give the DNR kudos for launching the study, and at least admitting that they don't know if Wisconsin is the same as the rest of the country so they will study it. They also may be looking at it as "ammo" to use against the Anti's argument that "wolves are cute and we can't hunt them." Of course they will not put it that way, but hide it in some sort of a study that will say wolves are not the problem. If you have to argue against such a study - the best way is to use another study of your very own stating the opposite outcome. At least it puts you on even ground at that point, and most ANTI studies are bogus and most judges see that - if you give them a valid study to measure up against.

Unfortunately, I think a lot of the bad wrap that the wolves get with regards to deer predation is that guys are upset that the wolves "get to kill MY deer". "I didn't see any deer this year - it must be the wolves' fault." I have heard it time and time again, but it is a hollow argument. There were a LOT of converging reasons that the deer hunt was a bummer this year, but the wolves were only a minor part. They may have helped push the deer to a nocturnal living - ie: they did not have a moment to rest during the wolves active hours, as well as they surely brought the pre-season numbers down some.

What everyone forgets is that the last 10 to 15 years we have had phenominal deer hunting. I don't recall a single hunter standing on a podium two years ago and preaching that "The DNR really pulled one off for us hunters this year!" Ten years before that we had dismal hunting the entire decade! I remember that we used to live in the woods and hunt HARD for 10 days straight. It was a great year when we had two deer on the meat pole, and I remember a couple of years that we did not shoot a single deer for 12 guys! I spent my first two years in the woods without even seeing a deer! There will be good hunting and there will be bad hunting, but the DNR is not to blame for either. We are hunters, and we should expect that we can't always connect with our hunted species.

As a varmint hunter, I think I may be preaching to the choir... I did not give up deer hunting even though I hunted from 12 to 23 years old before ever shooting a whitetailed deer! I have smacked a lot of deer over the years, but I never saw a single one this year during the gun season. I don't have any intentions, or even thoughts of quitting. I will look forward to it after a decade of never pulling the trigger. I still hunt preditors hard, and I still get warm all over when I see a coyote - even though it only happens about every 15th or so outing at best. The rarity of the opportunity is what makes it special!

We don't have to hunt to survive, we do it for the entertainment value. If you don't enjoy it without the kill, then get a job as a butcher and save the license costs! Of course the successful hunt is one of the best ways to spend time, but if it is not enjoyable without the successful harvest, then take up target shooting or join the army. There are much better things to do than hunting if you need immediate gratification!

I don't know where I got off track here, but I guess the point is the DNR is doing the right thing by conducting this survey. Let's hope it allows us to hunt the wolves and reduce their pressure on the deer (and more importantly the farmers). It will give us another ultimate hunt to look forward to, even if it is slow-going and long on hours in the field per connection. Wouldn't it be awesome to put the crosshairs just below a wolve's ear and begin the trigger pull sequence???????

[Fitter]

I had a two hour long conversation with the wolf project coordinator here for the U.P. a few years back and we talked about this very subject. We came to a momentary roadblock when I said that the predation of the whitetail may be more dramatic in one area than another and even devastating if not decimating to the overall herd at times. He disagreed at first and claimed that the wolves wouldn't hunt themselves out of food. I think that's where our conversation went astray since we know that a predator isn't going to walk away from lunch if it presents itself especially when the terrain throws the percentages in the predator's favor.

I don't have a problem with the wolves myself. I do have to say it was most un-welcome to see a wolf during firearm season but if you look at the upside you could say that if the wolves are around there is likely to be a deer....somewhere. I watched the deer herd here, which was way out of whack, crawl slowly from a herd of nuisance animals to not even seeing a deer track in the snow during the winter. That was one extreme to another and part of the basis of the conversation I mentioned earlier.

I hear you, predator, and I have a tendency to agree. I would love to see a wolf in the wild! However, I don't want enough around that the deer completely disappear. You need a healthy population (no - nuisance levels are NOT healthy!). Of all creatures, wherever they are on the food chain. The wolf population explosion is due to the deer population explosion and there is no other argument to be made. If the hunters were able to keep the deer in check, the wolves would not have such an easy living, and they would not increase in numbers. it is all a big circle that turns around on itself over and over again.

The right number of wolves in nature is that a person who reasonable wants to see one, could do some research and enter the right chunk of woods and IF LUCKY catch a glimpse of one exiting the vicinity after some hours of looking. To run into them on the road is too many! To be able to say "let's take a quick walk and I will show you my wolves" is WAAAAAY too many.