White-tailed Deer Studies in Northeastern Minnesota
Editor’s Note: The following is a summary from research being done by Drs. L. David Mech and Michael Nelson, Research Biologists with the Biological Resources Division of the US Geological Survey.
White-tailed deer have been intensively studied near Ely, in northeastern Minnesota, since about 1974 in conjunction with on-going research on wolves. The deer portion of the research has focused on deer population size, survival, mortality factors, movements, genetics, and social organization. The broad objective is to understand how deer survive on the north-central edge of their range in North America where they are preyed upon by wolves and harvested by humans. Live-trapping, radio-collaring, and radio-tracking are the primary techniques being used.
In 1986 and 1987 deer densities averaged 13 deer per mi2 near Ely but only about 5 per mi2 just 30 miles southeast near Isabella. Numbers in the Boundary Waters Canoe Area Wilderness are even lower, probably closer to 1 deer per mi2.
Wolf predation and hunting are the major causes of deer mortality. From 1974 through 1984, each year an average of 53% of radio-collared males and 21% of radio-collared females died. Of those that died, about 80% of the females and 30% of the males were killed by wolves. Hunting accounted for 53% of buck deaths. The average age of does shot by hunters was 4 years while that of bucks was 2 years old. As with most young wild animals, fawns have the lowest survival, only 30-50% survive their first year. In a two year study, wolves and black bears were the primary cause of early fawn mortality, divided about equally. A 1975-1997 analysis of wolf and deer numbers indicates that deer increased and decreased independently of wolf numbers.
The doe population in Northeast Minnesota produces an average of 1.6 fawns per doe. All fawns spend their first year with their mothers but after that, sons strike out on their own while most daughters remain with their mothers. Most deer migrate between summer and winter home ranges which averages 10 miles apart. Buck summer ranges average about 1 mi2 while doe ranges are two-thirds smaller at 0.3 mi2. During the fall, bucks roam an average distance of 2 miles from the center of their home range searching for does.
About 80% of does use their mothers’ home range for their entire lives. Sixty percent of bucks, however, establish new summer ranges when they are 1 year old. Yet, 95% of new home ranges are never farther than 24 miles from birth sites.
Genetic studies revealed that deer in the study area are the descendants of eleven different deer lineage’s, most probably entering the region after extensive logging at the turn of the century changed the forests to favorable deer habitat. Deer in the Ely, Babbit and Isabella area are very similar genetically but show slight differences from deer near Cook, Two Harbors and Grand Marais.
For further reading:
Mech, L. D. 1984. Predators and predation. In White-tailed deer ecology and management. R.E. McCabe and L.R. Jahn editors. Stackpole Books, Harrisburg, PA 17105.
Mech, L. D. and M. E. Nelson. 2000. Do wolves affect white-tailed buck harvest in Minnesota? Journal of Wildlife Management 64:129-136.
Nelson, M. E. and L.D. Mech. 1981. Deer social organization and wolf predation in Northeastern Minnesota. Journal of Wildlife Management, Wildlife Monograph No. 77.
Nelson, M. E. and L.D. Mech. 1986. Mortality of white-tailed deer in Northeastern Minnesota. Journal of Wildlife Management. 50(4):691-698.
Nelson, M. E. and L.D. Mech. 1992. Dispersal in female white-tailed deer. Journal of Mammalogy 73(4):891-894.
Nelson, M. E. and L.D. Mech. 1993. Prey escaping wolves, Canis lupus, despite close proximity. The Canadian Field Naturalist. Vol 107:245-246.
Nelson, M.E. 1993. Natal Dispersal and gene flow in white-tailed deer in northeastern Minnesota. Journal of Mammalogy 74(2):316-322.
Nelson, M.E. 1995. Winter range arrival and departure of white-tailed deer in northeaster Minnesota. Canadian Journal of Zoology 73:1069-1076.
Nelson, M.E. 1998. Development of migratory behavior in norther white-tailed deer. Canadian Journal of Zoology 76(3):426-432.
Nelson, M.E. and Mech L.D. 1999. Twenty-year home-range dynamics of a white-tailed deer matriline. Canadian Journal of Zoology 77:1128-1135.