GENERALIZED SUSTAINED YIELD TABLE FOR FREE-RANGING WHITE-TAILED DEER
This yield table is a comparison chart showing results using different deer management programs.
Michigan has a total of 58,000 square miles, 45,000 of which is suitable deer habitat. It has been estimated that the maximum carrying capacity is around 2.2 million deer or 48.9 deer per square mile. The desired population goal as stated by the DNR is 1.3 million. This is 60% of the carrying capacity or 28.9 deer per square mile. This 60% goal is a proper goal. Many studies have shown that this population density will produce the maximum sustained yield, while at the same time insure deer health and the habitat, with normal maintenance continuous forage productivity.
The sustained yield chart shows an increase of harvestable deer while even having fewer deer (90% density versus 60% density). Available data gives results from 100% density to 10% density. For our needs we will compare 100%, 90%, and two types of 60% deer management.
The data shown is from many years of research at the enclosed George Reserve in Michigan by Professor Dale McCullough and his associates. Professors Robert L. Downing and David C. Guynn, Jr. used Professor McCullough’s model at Clemson University, South Carolina with adaptation to free-ranging deer. The 60% QDM data is further adapted to conform to known results using a high grade QDM program.
The 100% deer density management reflects conditions where no hunting is allowed. Because no bucks are harvested, the buck-to-doe ratio drops to 1:1.1 and the bucks are allowed to die of old age. The population density stays somewhat stable; however, the habitat gets stressed, lowering the number of deer that can be supported through the years. The deer are stressed from population density and lack of proper nourishment to the point where as many deer die and disperse as there are born. Note the low number of fawns born (39.6) versus 53.6 at 90% density traditional bucks only harvested chart. This condition seen at large federal preserves is not a pretty picture.
The 90% traditional bucks only harvested chart reflects the deer management that has been in place for the most part in Michigan until the late fifties, where a legal buck needs to have at least one spike a minimum of 3" long. With bucks only being harvested, the buck-to-doe ratio changed to 1:3.3. The fawn crop increased 26% (53.6) with 10% less deer. The deer are still being stressed and this is shown by the same low adult doe-to-fawn ratio (1:0.77) and the buck harvest crop is subject to a varied number from year-to-year depending on weather conditions. The losses from mortality and dispersal remain high at 45% (40.8) and this is primarily due to the high deer density and its consequences.
The 60% traditional bucks and does harvested is pretty much due to the deer management that is in place or intended to be in place throughout Michigan presently. This 60% bucks and does harvest program graphically illustrates how you can have more by having less. The 12.9 bucks harvested versus the 12.8 at 90% is unchanged. Total harvest now is 28 (220% increase). The deer are healthier and larger (records are broken constantly) and the deer harvest numbers are more constant. Blips will occur, but the overall picture shows steadiness. The data as shown is not only true but also very interesting. It shows a 1:2 buck-to-doe ratio which, incidentally, may be misleading and not believed by some. This ratio is true but only true if no more than 70% of the bucks are harvested. Unless there are natural conditions or a rule in place that protects at least 30% of the total buck population, this whole data column is not valid. This also applies to the 90% - 1:3.3 ratio. Conditions in some areas of the Upper Peninsula may satisfy the 30% minimum protection requirement.
In the past we have heard statements by the DNR of a 1:3 buck-to-doe ratio. Lately, we hear claims of 1:2 or 1:2.5. In theory, and in some locations, these are correct. In high-hunter-density-areas, where up to 95% of all bucks are harvested, it’s not unusual to have a buck-to-doe ratio of 1:10. One offshoot of this is that it doesn’t get better. The excess number of adult does take charge of the area, disperse 90% of their male yearlings, and keep wandering young bucks from other areas from settling in. The only bucks allowed are the gigolos temporarily used for breeding.
Another interesting fact in the 60% program is that yearling does now have fetuses on May 1st. This is due to the population density stress being removed. This does not help the Upper Peninsula yearling doe. She rarely, if ever, becomes pregnant as a fawn due to the short summer and long, cold winter (weather stress). Notice the adult doe-to-fawn ratio that now has doubled to 1:1.46 versus the 90% density. These adult doe-to-fawn ratios keep right on improving through a 10% deer density condition with a 1:2 ratio.
Take a look at the lowered yearly non-harvest losses. With only 33% less deer the mortality rate drops 65% (40.8 versus 14.2). This results in a rate of recruitment increasing to 47%. The 47% rate of recruitment (28 deer) means this is the number that should be harvested to maintain high deer productivity. Not harvesting an adequate number of anterless deer quickly puts you right back into the stressed 90% low quality group.
How about those fawns? Should we protect any, including the button-buck? With a 60% density program, you are insuring a surplus of fawns being born (42.2) for a recruitment of 28 (yearly harvest). The surplus 14.2 fawns equal the non-harvest losses. Some of these fawns will be lost shortly after birth; some from accidents, others from winter and nutritional stress, and others to grow into adults but still are a non-harvest loss later in life. The 5.8 fawns need to be harvested or they add to the population. Do not replace these fawns by harvesting additional adult does. They are needed for production. It is okay to protect button-bucks. It is not a catastrophe if one is taken.
Who turned the light on and let this advanced and much improved deer management style be our present day practice? We owe much gratitude to the many DNR, university, and private biologists, living and deceased, who pioneered deer research. However, the job is not quite yet done! There is nothing in place to insure protection of at least 30% of the adult bucks, and this is not a high protection rate. There should be a natural buck-to-doe ratio of 1:1.3. There should be an emphasis on the health of the deer through ensuring year-round nutritious forage whether on public or private land.
The 60% Quality Deer Management (QDM) Program is the next step up in deer management. The main focus of QDM is the welfare of the deer population. The QDM goal is a large, healthy and consistent fawn crop (44.6). The key to this goal is a healthy doe population generating a high adult doe-to-fawn ratio (1:1.8). What about this concept of protecting young bucks that QDM is so often associated with? Well, it is important and necessary. The natural 1:1.3 adult buck-to-doe ratio won’t happen without it. But ask yourself this question. What good will it do to protect young bucks in a deer herd that is nutritionally and population density stressed? Those young bucks you protected will probably move on to greener pastures.
There is very little difference in 60% traditional and 60% QDM production rates. The rates are higher with QDM and this is partly due to the 1:1.3 buck-to-doe ratio. With older bucks being present, the social order becomes normal. The rut intensifies and starts at the right time. This insures that all or most adult does get pregnant their first estrous. More doe fawns get pregnant. This is not necessarily viewed as a positive, except it does indicate a healthy fawn crop. All these fawns born at the same and right time lowers the predation (safety in numbers) and these fawns have access to early, more nutritious forage. This all adds up to more and healthier fawns entering the winter season in good shape, thus improving survival.
Harvesting no more than 10% of the yearling bucks and about 80% of the older bucks assures the appearance of the older dominant buck. This guy is important in controlling the social order and suppressing the breeding instincts of lessor bucks thus assuring the passing of better genes. The table shows a lower buck harvest (10.3) versus the 60% traditional (12.9). This is the trade-off in achieving a healthier and balanced deer herd. Buck sightings soar due to the same young buck being seen again and again. This experience is new and exciting. You wonder what he’ll be like next year!
As in the 60% traditional, the 60% QDM program requires an adult doe and fawn harvest. The 1:1.1 buck-to-doe harvest ratio is necessary to maintain the balance. This ratio has been proven through many years of experience. Notice the 9.4 fawns that need to be harvested. Be observant and count the fawns in relation to does. Are 80% or more of the adult does with fawns? Do the doe/fawn families consist of at least 50% twin fawns? If the answers are yes, you may need to harvest 9.4 fawns per 10.3 total bucks harvested to maintain the 60 quality deer being present the following spring. If you are located in high-stress areas like the Upper Peninsula where the winter kill will selectively crop them off naturally, leaving the hardiest, you may want to contact your local DNR biologist for advice. Remember 8 fawns already have been allocated to non-harvest losses.
The numbers as shown are accurate. The need to follow them is important. Following them exactly is not important. Over-harvesting to a 40% or 50% density causes no harm. Under-harvesting temporarily up to 70% density is acceptable. Be alert for the flashing red lights. Note any changes like lower dress weights, lower adult doe -to- fawn ratios and a change in the buck-to-doe ratio. Watch closely the adult doe harvest (the KEY element). If the adult doe harvest consists of more than 50% 2½ yr. olds and younger you are harvesting too many does and keep a keen eye on the browse damage, for you have just become a deer manager!
Good luck and keep the fun in hunting!
President, Mid Michigan Branch QDMA
Phone (810) 784-8090
Web Page http://members.tripod.com/~mmbqdm/index.html<
For information on the Quality Deer Management Association, Phone its National Office at 1-800-209-DEER.
|GENERALIZED SUSTAINED YIELD TABLE FOR FREE RANGING WHITE-TAILED DEER|
|DEER DENSITY AND HARVEST METHOD||DATA IN SPRING PRE-BIRTH, MAY 1st||DATA AT BIRTH||YEARLY NON-HARVEST LOSSES THRU MORTALITY AND DISPERSAL||RATE OF RECRUITMENT OCTOBER 1st||YEARLY HARVEST|
|MALES: ADULTS AND YEARLING||FEMALES: 1 YEAR||FEMALES: 2 YRS+||BUCK TO DOE RATIO||FETUS'S YEARLING DOES||FETUS'S ADULT DOES||TOTAL FAWNS BORN||ADULT DOE TO FAWN RATIO||MALE FAWNS %||ADULT MALES||ADULT FEMALES||FAWNS||TOTAL||%||TOTAL No.||ADULT MALES||ADULT FEMALES||FAWNS||TOTAL|
|100% NONE||48||8||44||1 : 1.1||0||39.6||39.6||1 : 0.76||58||11.04||7.8||20.8||39.6||0||0||0||0||0||0|
|90% TRAD. 70% BUCKS ONLY||20.7||10.8||58.5||1 : 3.3||0||53.6||53.6||1 : 0.77||58||2.08||10.6||28.1||40.8||14||12.8||12.8 VARIES||0||0||12.8|
|60% TRAD. 70% BUCKS & DOES||19.8||12.9||27.3||1 : 2||2.2||40.0||42.2||1 : 1.46||52||2.3||5.5||6.4||14.2||47||28||12.9 CONST.||9.3||5.8||28|
|60% QDM SELECTIVE||15; 1 YR 11; 2 YR+ 26; TOT.||12.2||21.8||1:1.3 NATURAL||5.4||39.2||44.6 QDM GOAL||1:1.8 QDM KEY||52||2.4||3.2||8.0||13.6||52||31||1.5;1 YR 8.8;2 YR+ 10.3;TOT.||11.3||9.4||31|
|QDM BUCK TO DOE HARVEST RATIO IS 1 : 1.1|
|CHART DATA IS FROM PROFESSOR DALE McCOLLOUGH'S RESEARCH AT GEORGE RESERVE MICH., (AN 1100 ACRE ENCLOSURE). IT HAS BEEN UPDATED TO APPLY TO FREE RANGING DEER AT CLEMSON UNIV. S.C. BY PROFESSOR ROBERT L. DOWNING AND PROFESSOR DAVID C. GUYNN JR..|
|60% QDM DATA REFLECTS A HIGH GRADE QDM PROGRAM PROTECTING 90% OF YEARLING BUCKS, HARVESTING 80% OF 2 1/2+ YEAR OLDS AND HAVING A BUCK TO DOE RATIO OF 1 : 1.3 (NATURAL RATIO). HARVESTING AN ADEQUATE NUMBER OF BOTH DOES AND FAWNS IS VITAL. HABITAT IS MAINTAINED WITH CUTTINGS AND PLANTINGS FOR YEAR ROUND NUTRITIOUS FORAGE.|
|90% TRADITIONAL 70% BUCKS ONLY HARVEST SHOWS A BUCK TO DOE RATIO OF 1 : 3.3, AND 60% TRADITIONAL 70% BUCKS & DOES HARVESTED SHOWS A BUCK TO DOE RATIO OF 1 : 2. THESE SENSIBLE BUCK TO DOE RATIOS ARE ACCURATE AS CLAIMED BY MOST STATE DNR AGENCIES, BUT ARE ONLY TRUE IF A 70 % MAXIMUM BUCK HARVEST IS ACCOMPLISHED. IT IS IMPORTANT TO ENFORCE THIS CRITICAL FUNCTION. IT IS VERY EASY TO GET A SKEWED 1 : 5 OR WORSE BUCK TO DOE RATIO IN A HIGH HUNTER DENSITY AREA WHERE TOO MANY BUCKS AND NOT ENOUGH DOES ARE HARVESTED. IF YOU ARE NOT SEEING ANY BUCKS, THERE'S A REASON FOR IT. AS PROFESSOR DAVID GUYNN ONCE TOLD ME "IT'S BECAUSE THEY'RE NOT THERE".|
|ED SPINAZZOLA PRESIDENT MID-MICH. BRANCH QDMA|