Begins Dec. 1 and runs for 14 days

Status/Trend UPDATE: March 2006.  Click here..

The 2004 posthunt deer population in Colorado was estimated to be 600,900.  The 2004 statewide objective for mule deer was 630,000.  After a series of mild winters, deer herds appear to be increasing across much of the state.  Over 80% of the deer in Colorado are found west of the Continental Divide.  It is estimated that white-tailed deer, found almost exclusively on the eastern plains, make up less than 3% of the statewide deer population. 

All deer licenses in Colorado became limited in 1999 because of concern about declining deer populations and low buck:doe ratios.  Prior to 1999, most licenses for antlered deer had been unlimited and issued over-the-counter.  As a result of limitations, the number of deer hunters in Colorado dropped from an average of 185,300/year from 1980-1998 to 84,400/year from 1999-2005 and statewide harvest dropped from an average of 64,000 deer/year to 36,600 deer/year during the same periods.  Concurrently, average annual hunter success rates increased from 34% to 43%.  Observed, posthunt buck:doe ratios (i.e., bucks/100 does) prior to limitation were between 10-20 for most units in the state.   Since limitation, buck:doe ratios have increased significantly in most units.   In 2004, the mean statewide posthunt buck:doe ratio was 31 calculated by weighting observed ratios by estimated posthunt population size.  Along with the increased buck:doe ratios, deer hunter satisfaction in Colorado has increased greatly, particularly among organized hunting groups, and mature bucks make up a larger proportion of the harvest.  Even so, demand for limited deer licenses in many units has remained relatively low.  In most units, hunters have an opportunity to draw a deer license without preference points.   Some Colorado deer hunters appear to have shifted to elk hunting, where unlimited licenses are still available, whereas others appear to have stopped hunting big game in Colorado altogether.

The decline in Colorado’s deer populations in the 1990’s appeared to result primarily from reduced early fawn survival.   During this period, posthunt fawn:doe ratios steadily declined in most of the state with the exception of the eastern plains.  Radio-telemetry studies of early fawn mortality in western Colorado indicated that disease and malnutrition were at least as important as predation in reducing early fawn survival.  Another study showed that improved nutrition and condition of does during the winter resulted in higher survival of fawns the following summer.  Improved nutrition and condition of fawns during the winter resulted in highly significant increases in survival.  The predation rate on fawns was inversely related to fawn nutritional status and condition.  A study is currently underway to evaluate the effects of habitat manipulation on fawn survival and deer density.

Although a full analysis is still pending, there does not appear to be a clear relationship between reduced buck harvest and posthunt fawn:doe ratios (i.e., fawns/100 does) in Colorado.   In some units where major reductions in hunter numbers resulted in large increases in buck:doe ratios, fawn:doe ratios have remained low.  Conversely, in some units with only minor reductions in hunter numbers and small increases in buck:doe ratios, fawn:doe ratios have increased considerably.  In many units, observed fawn:doe ratios went from being consistently low in the late 1990’s to showing considerable year to year variation since 2000.  In 2004, the mean, posthunt statewide fawn:doe ratio was 58 calculated by weighting observed ratios by estimated posthunt population size.

Colorado estimates posthunt deer populations each year.  Estimates are derived using spreadsheet population models on the basis of Data Analysis Units (DAUs) that represent relatively discrete deer herds.  The population models use probabilistic harvest data (estimated using random phone surveys) and observed posthunt sex and age ratios (estimated using helicopter flights) as the primary inputs.  In addition, in 4 representative DAUs, annual doe survival rates and winter fawn survival rates are estimated each year using radio-collared animals and stratified, random quadrat surveys are periodically used to derive probabilistic population estimates.   Kaplan-Meier survival rates from these DAUs are used as the basis for calculating survival rates in other DAUs with similar habitat.   In 2004, 62,173 deer were classified by sex and age, annual doe survival rates averaged 81.5%, and winter fawn survival rates averaged 77%.

Since deer licenses were limited in 1999, doe harvest has been a controversial issue in western Colorado and there have been objections to increased harvesting of does in some areas.   In the early 1990’s, doe harvest in Colorado ranged from 20,000–30,000/yr.  By the late 1990’s, antlerless deer harvest decreased below 10,000/yr where it has remained through 2005.  As populations increase and exceed population objectives, increased doe harvests will likely be recommended in the future.

Chronic wasting disease CWD) has been documented in Colorado’s deer and elk herds since 1980.  CWD is known to occur in most units in the northern half of the state and appears to be gradually spreading to the south especially along the Front Range.   With the exception of Grand Mesa, CWD has not been found in southwestern Colorado.   Since 2002, prevalence rates in affected units have typically been < 2% but have been found to be as high as 7.6% in the northeastern part of the state.  In some northeastern units, deer numbers have been significantly reduced by culling, liberal hunting seasons, and increased bag limits in an attempt to reduce transmission rates.   Thus far, there is no clear evidence that CWD is having a major impact on Colorado’s deer populations.  However, studies are not yet complete and population effects may be difficult to detect.   This is compounded by the fact that CWD appears to affect older-age bucks at a significantly higher rate than it does females and younger males.  Colorado offers CWD testing of hunter-killed deer and elk for a nominal charge.

Additional information about Colorado’s deer herds, harvest data, and CWD can be found on the Colorado Division of Wildlife’s website at www.wildlife.state.co.us.