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Know CWD website

Know CWD [exit DNR] General information about CWD in Wisconsin including common misconceptions.

Contact information
For information on CWD, contact:
Timothy Marien
CWD wildlife biologist
Bureau of Wildlife Management

Former CWD management zone population

Monitoring changes in deer populations in the former chronic wasting disease management zone (CWD-MZ) is important for understanding changes in CWD transmission and prevalence rates and the effectiveness of management efforts. Trends in the size of the deer population in the CWD-MZ are being monitoring using a combination of helicopter and fixed-wing aircraft surveys and population modeling.

Fixed-wing survey methods

  • Surveys consist of transects oriented east-west that extend across the length of DMUs.
  • There are three people in the fixed-wing aircraft: the pilot and two observers. Diagram of observation areas [PDF]
  • Transects are spaced two miles apart on the centerline. Transects are 1/4 mile wide, about 200 yards are searched on each side of the plane.
  • Average speed is 95 mph.
  • Transects are flown when there is at least 4-6 inches of snow cover.
  • Currently, over 4,200 miles are flown each winter, surveying 17 DMUs in the CWD management zone.
  • The surveys do not directly provide a population estimate, but an index of relative abundance.

Helicopter survey methods

Helicopter surveys have not been done for the last couple of winters but may be continued in the future.

  • Randomly selected square mile quadrats are surveyed, covering about 20-30 percent of the study area.
  • There are three people in the helicopter: the pilot and two observers.
  • Transects are flown when there is at least 4-6 inches of snow cover.
  • Depending on wind conditions, transects are either flown north and south or east and west.
  • Enough transects flown in each section to be able to see all areas of the section.
  • Fly around 100ft above tree tops at 30-35 mph.
  • The location and number of deer are recorded on aerial photos.
  • Care is taken to prevent double counting of running deer.

Deer population trends

Current analyses that incorporate data from helicopter and fixed-wing surveys with historic harvest data suggest that the deer population in the CWD-MZ increased substantially during the 1990s, peaked at over 200,000 in 2002, and has been slowly declining since then.

Last revised: Wednesday February 07 2018