# Antler Morphometry in a Colorado Mule Deer Population

> How much can a deer’s antlers tell you? Measuring more than 1,200 mule deer in Colorado through the 1960s, two researchers found left and right antlers almost always match, antler weight climbs by about 24 grams a month of age, and several drier years with less winter browse left surprisingly little mark. They suggest that weighing yearling antlers, or even shed antlers, could help managers read the age and condition of a herd.

Summary by Kersey Lawrence, Original Wisdom. Updated 9 November 2026. Page: https://www.originalwisdom.com/tracking-literature/1969-anderson-medin-antler-morphometry-colorado-mule/

## Citation and access

- **Authors:** Allen E. Anderson and Dean E. Medin
- **Year published:** 1969
- **Journal or source:** The Journal of Wildlife Management
- **Full citation:** Anderson, A. E. and Medin, D. E. 1969. Antler morphometry in a Colorado mule deer population. The Journal of Wildlife Management 33(3): 520–533.
- **DOI:** 10.2307/3799374
- **Access status:** Publisher link only
- **Where to find it:** https://doi.org/10.2307/3799374

## Tags

- **Species:** Mammals > Mule deer
- **Region:** North America > United States
- **Tracking:** Scat; Sign surveys; Tracking
- **Methods and technology:** Analysis of variance (ANOVA); Chi-square test; Descriptive statistics; Linear regression; Plot searches
- **Data type:** New field data
- **Observer qualification:** Not reported
- **Discipline:** Behaviour and ecology
- **Year published:** 1969

## Detailed keywords

- **Species:** Studied: Rocky Mountain mule deer (Odocoileus hemionus), antlered males. Winter-range browse plants measured: true mountain mahogany (Cercocarpus montanus), antelope bitterbrush (Purshia tridentata) and big sagebrush (Artemisia tridentata). Discussed from other studies: black-tailed deer (O. h. columbianus), white-tailed deer (O. virginianus), fallow deer (Dama dama), roe deer (Capreolus capreolus), red deer (Cervus elaphus), and cattle in the northern Great Plains.
- **Location and habitat:** About 528 square miles of the Cache la Poudre River drainage, within or next to Roosevelt National Forest, north central Colorado, United States. A South Platte tributary rising on the Continental Divide and flowing east through the Front Range; rugged to precipitous terrain at about 5,500 to over 12,000 ft. Three winter-range study areas of about 500 acres each, at 5,800 to 7,100 ft, 6,600 to 7,760 ft and 7,440 to 8,760 ft. Migratory deer population; winter range below about 8,500 ft.
- **Topics:** antler morphometry; left and right antler symmetry; antler points, spikes and brow tines; inside antler spread; beam diameter, length and weight; antler weight as an index of physical condition; antler weight in relation to age and carcass weight; year-to-year differences in antler development; precipitation, soil moisture and winter browse yields; deer density indices from fecal (pellet) group counts; age estimation from tooth replacement and wear and from dental cementum; hunter check stations; sample size adequacy; possible management uses (estimating carcass weight and the age structure of antlered males, including from shed antlers).
- **Statistics or models:** Paired t-tests; chi-square tests; F-tests (analysis of variance) with Duncan’s New Multiple Range Test; 95% confidence limits; simple and multiple linear regression and correlation; log-log (curvilinear) regression of antler weight on eviscerated carcass weight; coefficients of variation; sample size adequacy tests (Snedecor 1946); double sampling of browse yields; Ferguson (1955) pellet group formula, assuming 13 fecal groups per deer per day. Internal differences to note: the abstract gives “over 1,200” deer for the symmetry tests, while the samples in Tables 1, 2 and 4 to 6 for the two age classes total 1,192, 1,219 and 1,133; the abstract speaks of 25 yearling and 30 older “deer”, while Table 8 counts “beams”. The deer used for antler weight against age (Fig. 1) are described as about 15 to 77 months, the left and right weight comparison as 15 to 82 months, and the brow tine regression as 16 to 121 months.
- **Data type:** New field data, 1960 to 1965: a voluntary hunter check station sample (58 days over six hunting seasons, 1960 to 1965) and twice-monthly collections of deer shot throughout the drainage (1961 to 1965). Browse yields from the fall of 1962; precipitation and soil moisture 1961 to 1964.

## Synopsis

### 1. What they did

Antlers are often used to judge the condition of a deer herd, but little had been measured for Rocky Mountain mule deer from one large population of known ages. The authors asked whether left and right antlers are the same size, how antlers change with age, whether they vary from year to year with rainfall and winter food, and which simple measurements best predict antler weight.

They worked with the migratory mule deer of the Cache la Poudre River drainage in north central Colorado, from 1960 to 1965:

- Check station sample. Antlers of hunter-killed deer were measured at a voluntary check station over six hunting seasons. Deer were aged by tooth replacement and wear and grouped into three age classes: 16 to 18 months (yearlings), 28 to 30 months, and 40 months or older.

- Collected sample. Deer shot twice a month throughout the drainage from 1961 to 1965 were taken to the laboratory, aged to the nearest month from tooth cementum, and weighed. Their antlers were sawn off within 8 hours of death and weighed.

- Measurements. Beam diameter 2.5 cm above the burr, beam length, inside spread, the number of points (2.5 cm or longer, not counting brow tines), and the presence and length of brow tines.

- The environment. On three winter-range study areas they measured yields of the three main winter browse plants, weekly precipitation and soil moisture. They estimated deer numbers by counting and clearing deer fecal (pellet) groups twice a year on permanent 100 square foot plots.

### 2. What they found

Left and right antlers

- Of 36 paired tests on beam diameter, length and number of points in the two younger age classes, only three showed a significant difference, close to the two expected by chance. Left and right antlers were essentially symmetrical.

- In 25 sets of antlers, left and right beam weights did not differ.

Points, spikes and brow tines

- Among 646 yearlings with symmetrical, normal antlers, 14.9% were “spikes” with one point per beam. The yearly share of spikes ranged from 6.3% (1964) to 22.6% (1961), a significant difference.

- About 6% of 820 yearlings had six points and 0.1% had eight.

- Brow tines became more common with age: 5.9% of 845 yearlings, 43.3% of 374 deer aged 28 to 30 months, and about 77% of deer 40 months and older (Table 2). Among 28 to 30 month old deer, brow tines varied from 26.7% (1961) to 55.6% (1965).

- Antler weight was closely related to brow tine length (r = 0.80).

Year-to-year differences

- Beam diameter, beam length and number of points all differed significantly between years. In general they were lowest in 1961 and similar in the other years. Together with the many spikes and few brow tines that year, this suggests antler development was relatively poor in 1961.

- From 1961 to 1964, rainfall, soil moisture and browse yields mostly fell, with three- to fivefold drops in mountain mahogany and bitterbrush. Deer numbers stayed stable or rose slightly. Antler development did not appear to follow these changes.

Predicting antler weight

- Beam weight was the most variable measurement and beam diameter the least.

- In yearlings, beam length was the best single predictor of beam weight (r = 0.82); in deer about 27 months and older, beam diameter was best (r = 0.82). The number of points was the poorest predictor in both.

- Combining diameter, length and points improved prediction only slightly for yearlings and not at all for older deer. The measurements were only fair predictors of the highly variable antler weight.

Weight, age and body size

- In 23 collected deer, total antler weight rose in a straight line with age, by about 24 g per month (r = 0.94). Variation grew with age, especially after 40 months.

- Antler weight rose steeply (curvilinearly) with eviscerated carcass weight (r = 0.85).

- Antlers made up 0.2% to 1.9% of bled carcass weight. One set still in velvet, from a 73-month-old deer, weighed 4.33 kg, 3.9% of bled and 5.2% of eviscerated carcass weight.

Sample size

The yearly yearling samples were large enough for the chosen precision (5% of the mean), but samples of 28 to 30 month old deer were often too small. About 210 yearling beam weights would be enough.

### 3. What they concluded

- Left and right antlers can be treated as essentially the same.

- The environmental factors they measured were not strongly related to average antler development. This may be because the measurements were not precise enough, or because other factors masked the effect: the winters were mild and other foods were available, overall diet quality (protein, phosphorus, calcium) may matter as much as browse quantity, and the deer spend late antler growth on what appears to be excellent summer range.

- Year-to-year differences in antler development may be hard to detect in migratory mule deer, and more evidence is needed. Antlers may still be useful for comparing areas with large differences in habitat or deer density.

- The weight of a single yearling antler beam may be the most reliable and sensitive measure of male condition or environmental change: yearlings respond more to stress, are easily aged, are plentiful and have little trophy value, and a single beam is a direct and precise measure.

- The relationships between antler weight, carcass weight and age need testing in other populations, which may need their own prediction equations. Possible uses are estimating the carcass weight of antlered males when other body parts are missing, and estimating the age structure of antlered males on a winter range by weighing a sample of shed antler beams.

### 4. How tracking was or was not used

The study is about antlers, not tracking. The only use of signs was to estimate deer numbers: fecal (pellet) groups were counted and removed twice a year on permanent 100 square foot plots, and the counts were converted to deer per square mile using an assumed 13 fecal groups per deer per day.

### 5. Tracker or observer certification

Not reported. The paper does not say who counted the fecal groups. These counts were used only as a background index of deer density, not for the main findings.

### 6. Other technologies, skills or innovations

- Ageing deer to the nearest month with the dental cementum technique, assuming a June birth date.

- Standard antler measurements adapted from the Boone and Crockett Club scoring system, with beam diameter used instead of circumference because it was easier to measure accurately at a check station.

- Most analyses were run on an IBM 1401 digital computer at the Colorado State University Statistical Laboratory.

### 7. Implications for conservation (from the paper)

- If antlers are used to judge male condition or environmental change, the weight of single yearling beams may be the most reliable and sensitive measure.

- Antler development may still help compare regions with large differences in habitat or deer density.

- Data from shed antler beams may help assess the effects of habitat management, harvest density or climate on the age structure of males.

### 8. Implications for tracking (Original Wisdom's observations)

_These are Original Wisdom's observations, not the authors'._

- Shed antlers are signs that trackers find in the field. The paper’s strong link between antler weight and age suggests that, in a population where it has been measured, the weight of a shed beam can hint at the age of the deer that dropped it, while variation grows in older males.

## Cite this summary

Lawrence, K. 2026. Summary of: Antler Morphometry in a Colorado Mule Deer Population (Anderson and Medin, 1969). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/1969-anderson-medin-antler-morphometry-colorado-mule/