Harvesting Does

As October 1st, 2019 looms on the horizon, hunters across the state are preparing for opening day of the whitetail deer hunting season. Licenses and tags along with extra doe tags, where they are available, will be purchased.

State goals for the Iowa deer herd have been to reduce the deer population to numbers matching levels that existed in the mid 1990’s. Iowa’s hunters have done an excellent job of reducing deer numbers to the goal developed by the deer study advisory committee in 2009. This level provides a good balance between the desires of hunters and the concerns by citizens about overabundant deer.

Each year the Iowa Department of Natural Resources releases the number of extra doe tags that are available by county. If you’ve been following any of the trends in doe harvests, you’ll have noticed that some counties do not have any extra tags available; the reduction in the antlerless quotas, the elimination of the January antlerless season as well restricting hunters in 27 counties in northwest Iowa has allowed deer numbers to stabilize.

What benefit are we gaining by harvesting these does, and are there any negative impacts with these extra tags that are sold on an annual basis? “From a population management perspective, antlerless tag allocation is used to limit population growth”, said Iowa Department of Natural Resources Biometrician Andrew Norton. “Because a single buck can breed multiple does, harvesting bucks has relatively little impact on population growth rates; you essentially are only removing that individual from the population.”

Since a mature doe will give birth annually, usually to multiple fawns, removing does has a much greater impact on population growth rates. In a productive environment with limited predators, similar to much of Iowa, it is likely the deer population would grow up to 25% in a single year if there was no doe harvest.

TYPICAL DOE & BUCK MOVEMENT
“Deer are very social animals; they tend to stay in the same area for an extended period of time”, said Department of Natural Resources Wildlife Technician Jim Coffey. “These deer populations can get out of control and cause issues with vegetation and localized farming.”

A doe will have a fawn or two in one area and then her offspring will do the same within that same geographical area and it just keeps growing. Coffey called this the “rose pedal” affect. “I put a radio color on a fawn out at Waterworks Park and 12 years later I found the doe dead, 200 yards from where I originally put the collar on her”, he explained. “Though she probably roamed more than 200 yards in that time frame, it was perfect example of how these deer tend to stay in the same area throughout their lives.”

Does compared to bucks
Does typically have a smaller annual range, around 1 square mile, they tend to stay in their natal range their whole life; however, 10-20% will disperse on their first birthday. These can be very long range dispersals and have been documented to be over 100 miles, but generally are closer to the 10 mile range. This is thought to occur around the birthing season when their mother may abandon them or drive them off to isolate herself in order to enhance protection for her new fawns. Otherwise, the one year old does go on forays, likely when mother is giving birth, and then they may return to their core range.

Bucks generally have a slightly larger annual home range (although their core range can be contracted). Mature buck movement increases quite a bit during the rut when they break up from bachelor groups and are searching for does in estrus. Dispersal occurs a much higher rate in bucks (50-75%) compared to does, however, they do not travel as far, on average about 5 miles. Similar to does, bucks will stay with their mother until their first birthday at which time some will disperse. Bucks also have a second dispersal period, during the rut when they are 1.5 years old. Because they are subdominant it is thought aggression from other bucks permanently drives the 1.5 year olds out of their home range.

MANAGING DEER POPULATIONS
“If we discontinued doe hunting, across much of Iowa, deer populations would quickly grow to levels that would create unacceptably high conflict with agricultural depredation, deer-vehicle collisions, over browsing, and potential for disease transmission (Lyme disease and Chronic Wasting Disease)” explains Norton. This varies regionally, and areas across much of northwest Iowa, where populations are lower with less available habitat, it will take longer for an unregulated deer population to grow. “Because wildlife in North America is considered as a public trust, the DNR is tasked with conserving wildlife populations that are compatible with modern landscapes, and maximize the benefit to all stakeholders.”

In general, hunters need to harvest about 2 out of every 10 does in order to hold the population stable. As you can imagine this leads to the variable county antlerless quota. If doe densities are 5 per square mile, 1 doe would need to be harvested per square mile, compared to areas where there are 15 does per square mile, 3 does would need to be harvested.

Because deer are relatively prolific and successfully disperse long distances, as we’ve already mentioned above, if does are over-harvested in a particular area, populations can recover in a few years. “As an agency, the Iowa DNR attempts to use variable county antlerless quotas to stabilize regional deer populations at acceptable levels, and create consistent recreational opportunity”, added Norton. “Recreational opportunity provided by deer hunting is just as, if not more important than managing the deer population, and providing additional antlerless tags can further increase recreation opportunity.”

Creating recreational opportunity has additional benefits beyond recreation. Venison provides a source of healthy, natural food, and hunting has been demonstrated to develop a connection between the individual and their appreciation and involvement in conservation of our natural resources. Because most hunters are required to have hunter education and gain experience using a firearm, hunting can also promote gun safety.

Iowa has a healthy deer herd that all can enjoy. There will always be challenges to managing deer throughout the State, in urban areas and other refuges like State and County parks where restricted hunting opportunity exists. However, special hunts have been successful in reducing deer numbers in those areas. Iowa’s hunters play an important role in managing deer populations. Always report your harvest as required by Iowa DNR regulations, take care of the resource we have. The future of this great sport that we so enjoy lies in the hands of those that we mentor and bring up to respect and take care of the resource we have in Iowa. Whether you mentor your own son or daughter, or take time to share your knowledge with a novice hunter, young or old, rewards will last a lifetime. Good hunting!