Wisconsin Department of Natural Resources
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Fawns per 100 Does
 
 
   Fawn to doe ratios collected in late summer give information on fawn recruitment and survival and are used as an input into the formula for annual deer herd abundance estimation. Fawn to doe ratios were summarized using groups of county deer management units. County deer management units were grouped based on location, habitat characteristics, and deer demography. For additional Information….
 
  
 
Background
Fawn to doe ratios (FDRs) are used for monitoring deer population status because they provide information about fawn production and survival which are strongly influenced by the nutritional condition of the population. Fawn production is strongly influenced by food availability which is in turn affected by the size of the deer population and the quality of the habitat. In addition, survival of newborn fawns is often related to predation and the nutritional status of the doe.
 
Collection and analysis methods
Each August and September, DNR employees (Summer Deer Observation Surveys) and volunteers (Operation Deer Watch) across the state keep records of the number of does, fawns, and bucks they see in August and September. The ratio of fawns to does in each deer management unit (DMU) provides an index to current reproductive rates and is an essential component in the formula used to estimate herd size. Due to sampling limitations, FDRs are estimated annually for 9 county groupings.
 
Using the metric
County group FDRs are shown as average number of fawns per 100 does annually with a 3-year running average to assess trend. Average FDRs vary across Wisconsin, generally lower in forested regions than in farmland regions and higher after mild winters in the north. Low FDRs in some counties may reflect higher levels of predation on newborn fawns and populations that are closer to carrying capacity. This metric is an input into the formula that is used to estimate annual deer population size by DMU.
 
Limitations and precautions
No unbiased method has been developed to measure the number of fawns per doe in late summer deer populations. However, trends in roadside observations of does and fawns, especially in forested regions, have tended to match expectations based on other measures of nutritional condition of the herd and severity of winter weather. The precision (repeatability) of FDRs is a function of the number of does and fawns observed. At the DMU level sample sizes have often been relatively low.
 
Future needs
Assessing whether there are more efficient ways to estimate FDR data is on-going. Trail cameras may provide one avenue for producing FDRs for deer that are away from roads and during any time of the day and night.
 
Additional background materials related to this metric
FDR reports are available for viewing on the Wisconsin DNR website dnr.wi.gov keyword “wildlife reports”. Learn how to participate in operation deer watch by visiting the DNR website dnr.wi.gov keyword “operation deer watch”.

 
Fawns per 100 Does
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For questions on this deer metric data contact:
Jennifer Stenglein 608-221-6334 Jennifer.Stenglein@wisconsin.gov
Kevin Wallenfang 608-261-7589 Kevin.Wallenfang@wisconsin.gov