MEMORANDUM
DATE: April 2, 2002
TO: John Goss, Director DNR
FROM: Jim Mitchell Ph. D. Deer Management Biologist
SUBJECT: White-tailed deer reductions and resulting recovery of state parks' ecology
For the 9 years that span the deer reductions on Indiana state parks, I have participated in the evaluation of need for reductions, in the planning and implementation of reductions and in the evaluation of the reductions. Prior to the first reduction in any park (Brown County State Park) I recommended that park personnel collect deer harvest data whenever a deer reduction is implemented.
The data to be collected was the total number of deer removed, the number of hunter efforts required to remove the deer and the size of the area where the deer removal occurred. The collected data would enable the reductions on each park to be evaluated through time, would allow comparisons to be made between multiple parks and also would allow deer herd management on the parks to be compared to deer management on other properties in Indiana such as Military bases, Wildlife Refuges or Fish and Wildlife properties.
The basis for the recommendation was that harvest data are very economically collected, are quantifiable data, and are very sensitive predictive indicators of deer population trends. Additionally, harvest data analysis had been the exclusive data required to successfully manage the deer herds at levels compatible with maintaining vegetative diversity on 5 Military Bases (Camp Atterbury Army National Guard Training Site, Indiana Army Ammunition Plant - Charlestown, Jefferson Proving Ground - Big Oaks National Wildlife Refuge, Naval Surface Warfare Center - Crane, Newport Chemical Depot) and 1 National Wildlife Refuge (Muscatatuck National Wildlife Refuge) for many years prior to the first state park deer reduction.
The requested data had been used extensively for a significant time to successfully manage deer in Indiana on areas ranging in size from 6 square miles to 100 square miles. Park personnel have collected the requested harvest data for every state park deer reduction that has been conducted.
Dr. George Parker of Purdue University has independently evaluated the data that has been collected over the past 9 years for a total of 70 deer herd reduction events on 17 Indiana state parks. He has concluded that the technique (that has proven successful for the last 20 years of deer management on Military areas) should now be applied to deer management on Indiana state parks.
I have reviewed Dr. Parker's analysis, his conclusions and his
recommendations. I find his analysis to be accurate. I agree with his recommendation
that we should replace our criteria for implementing a deer reduction on each
state park that is currently based on annual analysis of vegetative damage with
a system based on harvest data.
I agree that our current system of park deer management, based on initiating
reductions only after documentation of existing damage, will result in our never
being able to prevent damage.
Now that we have reduced the intensity of the damage to our park vegetation, we need to take the next 2 steps: 1. although vegetative damage has been significantly reduced, it still exists and we must continue to reduce the damage, and 2. prevent future damage.
I agree with Dr. Parker that vegetative monitoring should continue on the state parks at intervals longer than annual so that the gradual improvement in vegetative condition can be evaluated and used to maximize the deer populations and minimize the deer reductions that are compatible with restoration of vegetative health to the parks.
It will be important to monitor vegetation in such a manner that we will be able to detect whether wildflowers (forbes) that are present when in the blossom stage are able to continue to survive to produce seed or whether the deer population is sufficiently high that the blossoms, immature seeds or the entire plants are consumed prior to producing viable seeds. Prior to the deer reductions on Indiana state parks, the high deer population ate all of the forbes prior to flowers being produced. Now that the deer populations are lower, we are documenting the return of flowers to the parks. The final goal should be a deer herd which consumes some of the flowers while leaving others to go to seed and complete the reproductive cycle.
By long term monitoring of the condition of vegetation on the parks and then correlation of deer harvest data with the vegetative data, we will be able to fine tune the level of harvest for each individual park that is compatible with the above goals.
In Indiana, we find that healthy female deer (does) have an average of approximately 1 fawn per year that lives beyond September to be recruited into the herd. Additionally, approximately half of the fawns are males and half females. Therefore, in Indiana, a deer herd that is not hunted will approximately double in size every 2 years . Certainly by the 3rd year, any unhunted deer herd will significantly more than double in size.
If we are to minimize the vegetative damage of deer in our parks while maximizing the number of deer available for park visitors to observe, the deer reduction should take place at least every other year. As we continue the long term vegetative monitoring as described above, we may find that although a reduction every other year may balance the ecosystem in some parks, the vegetation in other parks may not be adequately protected unless reductions are more frequent than every other year.
However, as deer reduction continues in our parks, we will continue to build upon our vegetative and harvest data bases to allow our deer management to continually improve.