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Population Management. Minnesota DNR divides the state into many administrative zones to manage the wildlife ( i ncluding deer). Minnesota DNR Administrative Areas. 36 Wildlife Administrative Areas or “wildlife work areas” as depicted by the black lines on the  area manager map

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population management

Population Management

Minnesota DNR divides the state into many administrative zones to manage the wildlife (including deer)

minnesota dnr administrative areas
Minnesota DNR Administrative Areas

36 Wildlife Administrative Areas or “wildlife work areas” as depicted by the black lines on the area manager map

Each has an area wildlife manager who makes decisions regarding deer management and provides recommendations regarding season setting. 

each state has its own system for determining populations
Each state has its own system for determining populations.
  • Systems used
    • Sex-Age-Kill– a census system based on bucks and antlerless deer harvested at ages 1 - 4 1/2 years old.
    • Pellet count – a census system based on droppings. A series of plots around a deer yard area. This system is very time consuming and costly. it is no longer used in Minnesota.
    • Trail count – a system of counting deer along trails.
    • Aerial count – airplanes or helicopters are used to count deer that can be seen from the plane. This system has been criticized for not being accurate.
    • Infrared photography
    • Simulation model – a computer used to evaluate the population dynamics of deer in the forested area
    • Proportion of fawns in prefawning population – the number of fawns in the spring divided by the total population.
possible systems continued
Possible Systems (Continued)
  • Proportion of adult males in prefawning population – the number of adult bucks divided by the total population.
  • Summer mortality – the proportion of deer that will die during the period from post hunting to pre-fawning (late November to mid-May).
  • Winter mortality – the proportion of deer that will die during the period from post hunting to pre-hunting (early June to late October).
  • Fawns per pregnant adult doe – the number of “new” fawns divided by the number of pregnant fawn does. Based on data collected from 1971-1981 describing the number of fetuses per pregnant doe and summarized according to DMU.
  • Winter severity index (WSI) – the number of days with 18” snow cover on the ground plus the number of days temperature is 0 F or less = WSI. Winter is mild if WSI = > 119, winter is moderate if WSI = 119-170, winter is severe if WSI = < 170.
minnesotas methods
Minnesotas Methods
  • In 2013, Minnesota currently has 129 deer permit areas. 
  • For each permit area, population goals are set using a public input process (5-10 year basis) and estimate populations on an annual basis. 
  • The DNR uses both population modeling and aerial surveys. 
  • Each year, aerial surveys are conducted on a portion of the DPAs to recalibrate the models. 
  • In farmland areas, the DNR uses distance sampling (instead of aerial surveys) to recalibrate the models. 
minnesota deer management
Minnesota Deer Management
  • Forest Wildlife Populations and Research Group
    • Manages the Northeastern forested area of Minnesota
  • Farmland Wildlife Population and Research Group
    • Manages the rest of the state
minnesota dnr forest wildlife populations research group
Minnesota DNR Forest Wildlife Populations Research Group
  • The role of the Forest Wildlife Populations and Research Group is to provide inventory information on wildlife populations, project how populations will respond to management, and develop a better understanding of how populations are impacted by changes in their environment

The forests of northern Minnesota create their own special blend of problems for wildlife managers and it is the responsibility of this group to help solve these problems.

  • Important wildlife species such as white-tailed deer, moose, black bear, grouse and furbearers are particularly difficult to inventory because of the enormous area they inhabit and the difficulty in observing these species in a forested environment. For these reasons, most species are monitored with a combination of surveys and computer simulation models. The group is responsible for designing and coordinating all surveys and analyzing the results. They have developed population models for most species that allow wildlife managers to project the outcome of specific management practices.

The ecosystems inhabited by wildlife are not static and the group conducts research to better understand how wildlife responds to its changing environment. The winters of 1995-96 and 1996-97, for example, were two of the of the most severe on record and research by the group was instrumental in understanding how deer responded. This research will provide long term information on how deer respond to increased logging on their winter range. The group is internationally famous for its work on black bear population dynamics and methods for managing and studying bear are used throughout the world.

mn dnr farmland wildlife population and research group
MN DNR Farmland Wildlife Population and Research Group
  • This group is responsible for providing information needed to manage major wildlife species in Minnesota's farmland zone which comprises all or parts of 74 counties and totals almost 49,000 square miles. To accomplish this responsibility, the group (1) coordinates and interprets population surveys; (2) conducts research which provides wildlife management information; (3) develops techniques needed to monitor and manipulate wildlife populations, manage critical wildlife habitats, and reduce or prevent wildlife damage; (4) evaluate management practices and programs; and (5) provides technical assistance and information to other DNR staff and the public.
mn dnr farmland wildlife population and research group1
MN DNR Farmland Wildlife Population and Research Group
  • Managing Minnesota's productive farmland deer populations requires information from several annual surveys. Reproduction is determined from examining over 300 does during the months of February through May. The age and sex composition of the deer harvest is collected by biologists at selected registration stations. And, car-killed deer information is summarized from peace officers and highway maintenance reports. All this information is combined with the registered deer harvest in a population model developed by the staff. Modeling results project deer densities and desired antlerless permit numbers for each of the 84 quota areas in the farmland zone.
research program evaluation and technical assistance
Research, Program Evaluation and Technical Assistance
  • The staff is presently involved in several timely research and evaluation projects. One field project, using radio telemetry, is attempting to determine deer population dynamics and movements in the vicinity of the Mille Lacs Wildlife Management Area. This information will be used to determine the potential impacts of late fall and early winter harvest of deer by American Indians allowed under the resolution of the 1837 Treaty court case. With this information, American Indians and DNR will be able to adjust harvesting regulations so that the area's deer populations will not be negatively impacted.
urban area deer
Urban Area Deer
  • Deer populations in urban areas present the need for unique management strategies. Over the last several years, we have evaluated the effectiveness, costs, and acceptability of several hunting strategies (e.g., sharp shooting, trap and shot, special hunts). Presently, a field study is using radio marked deer to better understand the population dynamics and movement of deer in an urban landscape. All this information should help perpetuate deer in our urban areas while reducing, to an acceptable level, problems caused by deer.
minnesota deer population estimating
Minnesota Deer Population Estimating
  • 2012 Report: The DNR will conduct aerial surveys over portions of the state later this winter. Population modeling, coupled with select aerial surveys, will be used to determine deer density. Management designations for 2013 deer permit areas will be determined once the new density estimates are compared to established population goals.
  • Upon estimating the final population they reduce this by 10% to ensure they are on the conservative (safe) side of the population estimate that may account for any errors or factors that may not be accounted for or over looked.
what is an appropriate population density to maintain
What is an appropriate population density to maintain?
  • Populations in land areas vary greatly and relies on a wide range of factors. Each area has its unique features of cover, openings, edges, browse and water. Each area must be analyzed on its own merits.
  • An area’s ability to sustain a healthy habitat depends on numerous factors.
  • Evidence of an overpopulated area is revealed by an increase in “road kill” reports and an increase in “nuisance” complaints filed by citizens.
what are mortality factors that affect white tailed deer populations
What are mortality factors that affect white-tailed deer populations?
  • Starvation
    • During winter months deer “yard up.”
      • Helps deer conserve energy
      • Avoid heavy winds
      • “Yardingup” also restricts their browse area and leads to over-browsing which in return leads to starvation.
    • During winter deer use up their body fat reserves and begin to suffer from malnutrition which also leads to starvation.
    • Severe winters where below 0 degree temperatures last for days and the snow is deep
winter severity index
Winter Severity Index
  • The Minnesota Department of Natural Resources measures the Winter Severity Index (WSI) by applying a point for everyday the temperature is below zero and applying a point for every day the snow is 15-inches or deeper.
  • A typical Minnesota winter scores a WSI of about 120.
  • Once the WSI begins to rise above that point, a winter is considered harsh, particularly if it reaches the 140 or 150 range.)

Winter severity, specifically snow depth and duration of snow cover, is the most critical factor affecting white-tailed deer survival in the northern forest. 

  • Deer movement is now heavily restricted, especially up in the border country.  Deer are in heavy conifer cover. 
  • With restricted mobility, wolf predation will increase as the tables have now turned against deer. .
  • Most common predators of white tailed deer include: wolves, hunters, and occasionally bobcats, bears and coyotes.
  • Old, weak and diseases deer are preyed upon as they are easier to catch
  • Predation alone does not severely reduce the deer population. Approximately 1.2 million white-tailed deer live in Minnesota.
  • Minnesota hunters harvested: 1991 2012
  • Firearms season 206,284 155,599
  • Bow and arrow season 12,964 21,556
  • Muzzleloader season 961 7,494
  • Total 220,209 184,649
  • Automobile collisions with white-tailed deer are significant in Minnesota
  • 2009 – over 2,600 collisions
  • 2010 0ver 1,900 collisions
incidental causes
Incidental Causes
  • Disease
    • Weakens deer making them more open to starvation, predation or accidents.
    • Many diseases are found in deer, among them brucellosis and leptospirosiscan be transferred to humans and cattle
  • Parasites
    • Parasites do not kill deer directly.
    • The most common parasite found in deer are the liver fluke, bladder worm and the throat bots.
    • Deer also host to the Deer Tick (IxodesDammini) that causes lyme disease in humans and dogs, but not the deer.
  • Competitors
    • Competitors such as the snowshoe hare compete for winter food with the deer.
    • Humans and livestock also compete with deer for food and space. Over Population
  • Overpopulation of deer causes stress and starvation.
what mortality factors affect black bear
What mortality factors affect Black Bear?
  • Predation
    • Predators mainly include humans. Small cubs have been known to be preyed upon by wolves and adult male bear.
    • In 2012, Minnesota hunters harvested 2,604 black bear.
    • Highest harvest was in 1995 – 4,956 bears taken
    • Approximately20,000 black bear live in Minnesota.
  • Incidental Causes
    • Bear rarely die from disease and parasites directly. Diseases and parasites will usually make the bear more susceptible to other mortality factors.
what mortality factors affect moose
What Mortality Factors Affect Moose
  • Parasites
    • Parasites in moose are often transmitted by white-tailed deer.
    • The most common and deadly parasite is the “brain worm.” It is transmitted to the moose by shared browsing and watering sites. The worm works its way to the moose brain and deteriorates it slowly.
    • Tick infestations can be serious if they cause the moose to rub off its coat, leaving bare patches which is dangerous for a moose during winter weather.
  • Disease
    • Moose are very susceptible to many diseases that are transmitted by livestock and white-tailed deer.
  • Incidental Causes
    • Malnutrition leading to starvation during severe winters is possible. Competitors for habitat such as white-tailed deer and humans lead to moose migration and possible loss of life because of reduced habitat.
  • Predators include: wolves, humans and occasionally bear may prey on young calves.
  • In addition to the chart (on right) in 2012 Indian Reservations issued permits and harvested 34 moose
what mortality factors affect wolves
What Mortality factors Affect Wolves
  • Disease
    • Diseases that kill wolves include: Rabies, Distemper and Parvovirus.
  • Predation
    • Predators of wolves are very few. Usually only young pups are preyed upon by eagles and occasionally bear. Adult wolves will kill other wolves if they intrude on their territory.
    • Wolves are no longer protected from hunting by the federal “Endangered Species Protection Act.” They can now be hunted by humans.
  • Wolves can go long periods without eating. Two weeks without food doesn’t weaken their muscle activity
  • Incidental Causes
    • Injury, pack stress, parasites and some diseases such as arthritis make the wolf more susceptible to predation, malnutrition, and accidental death.
what are common predators of large wildlife mammals in minnesota
What are common predators of large wildlife mammals in Minnesota
  • Coyote
    • Minnesota’s most abundant predator.
    • Prefer habitat is the transitional land area, but also live in prairie and dense coniferous forest.
    • They are omnivorous and can adapt readily to changing habitat conditions.
  • Coyote feed mostly on small mammals such as: snowshoe hare, mice, squirrels, grouse, muskrat, moles and small young livestock. They have also been found to prey on white-tailed deer (mostly fawns). Coyote generally consume deer meat that is carrion, a result of road kill, disease, starvation or another predator’s leftovers
  • The coyote population is stable in northern Minnesota and is increasing in density in southern Minnesota.
  • The coyote is often called the “Brush Wolf.” It should not be confused with the wolf.
other predators bobcat
Other Predators Bobcat
  • Bobcat
    • Prefer habitat in the northern third of Minnesota, specifically areas with heavy brush in dense timber.
    • Primary prey consist of snowshoe hare, closely followed by white-tailed deer.
    • Generally they do not east carrion and instead prefer fresh meat.
    • The are nocturnal and hunt solitary.
    • The bobcat is 20-30 inches at the shoulder and weighs between 15-40 pounds. It has a distinctive feature of short black tufts coming from the tips of its ears
other predators lynx
Other Predators - Lynx
  • Rare Wildcat in Minnesota
  • Prefer mature forests of northern Minnesota. The most northern counties in Minnesota are the southern boundary for lynx.
  • Primary prey and diet consists of the snowshoe hare. Occasionally will eat white-tailed deer.
  • It is larger than the bobcat, 2 feet at the shoulder.
  • Its most distinctive features include: long feathered ear tufts, ear to chin ruff and usually a pale grey or buff color with streaks of brown.
  • Primarily is a nocturnal hunter.
other predators wolf
Other Predators - Wolf
  • Takes advantage of weak, ill, old or diseased animals for prey. These animals are easier to catch.
  • Wolves usually hunt in packs with the alpha leading the hunt.
  • The dominant wolves will generally feed first, then allow the others to finish the remains.
  • Generally wolves will go without eating for 3-4 days. When they make a kill they will gorge themselves filling their large stomachs.
  • Wolves leave little remains of a carcass. Only large bones such as the spinal column, skull and large leg bones and hair are left for scavengers such as ravens, black birds and possibly coyotes.
other predators black bear
Other Predators – Black Bear
  • The bear is an omnivore and will eat animal matter such as: grubs, insects, worms, mice, snakes or nesting birds. Occasionally, but rarely, they prey upon larger mammals such as fawns, cubs, or young livestock.
  • Less than five percent of the bear’s diet consists of fresh meat.
  • The bear relies heavily on its senses in the search for food.
  • The bear is solitary in its search for food but will share common feeding grounds.
other predators humans
Other Predators - Humans
  • Humans prey on wildlife during highly regulated hunting seasons.
  • Reasons for hunting include:
    • food and fiber
    • population management of large mammals
    • monitor the environments
    • enjoy nature and the outdoors
    • provide funding for wildlife management programs
    • recreation
  • Poachers are humans that prey on wildlife during off seasons and illegally and unethically kill animals for economic gain.
what are the results of predation on wildlife populations
What are the results of predation on wildlife populations
  • Four results occur as a result of predation on wildlife populations:
    • Inferior prey animals are culled. These animals are typically old, weak, diseased, malnourished, or young.
    • Partial population control due to mortality caused by predator.
    • Stimulation of productivity in herds of prey animals. This is accomplished by eliminating the potential of over-browsed habitat by a high population which then results in better nutrition for the surviving animals which in return leads to better reproductive health.
    • Other wildlife populations are fed such as: ravens, coyote, bear, insects, fox, fishers, eagles, red squirrels, bobcats, etc.
what impact does large mammal disease and parasites have on large mammal populations
What impact does large mammal disease and parasites have on large mammal populations?
  • Most diseases and parasites do not have direct impact on the population. Instead disease and parasites may contribute to incidental mortality resulting from weakened condition caused by the disease or parasite. The exception are moose, they are more susceptible to death directly as a result of parasites or disease.
  • Some diseases and parasites carried by wildlife can be transferred to domestic animals and humans, such as: Lyme disease, brucellosis, rabies, leptospirosis. Many large mammals serve as host and do not actually become infected with the disease.