Sex Characteristics of Black-Tailed Deer Hooves

1. What they did

Hunters and biologists had long argued over whether a deer’s sex can be told from their tracks, with biologists usually saying no. The author had been noticeably better than chance at predicting the sex of deer when following fresh tracks to bedded deer in western Oregon. Size was one clue, and he also had the impression, shared by an earlier study of mule deer, that males’ hooves are wider towards the front than females’ hooves. Measuring deer tracks in Strawberry Canyon, near Berkeley, California, supported this: a histogram of track width at one-third of the length back from the tip showed two separate, fairly distinct peaks.

To test this on animals of known sex and approximate age, he measured the hooves of 106 black-tailed deer killed during a special hunt near Corvallis, Oregon, in late October and November 1961. At the check station, each toe was measured to the nearest half millimetre with a dial caliper:

• Total length of the toe.
• Arc width: the width across the toe where an arc, drawn on the bottom of the toe from the tip at one-third of the total length, met the toe’s edges.

Broken or malformed toes were left out. Deer were aged as fawns, yearlings or adults by tooth replacement and wear. The sample was 16 male and 20 female fawns, 21 male and 10 female yearlings, and 21 male and 18 female adults.

2. What they found

• A single hoof’s measurements were close to the average of all four. Individual toes sometimes varied a lot in size, but an unusually small toe was usually balanced by an unusually large opposite toe.
• Front hooves were about 3 percent larger than hind hooves, for both sexes and all ages.
• Fawns: no difference between males and females.
• Yearlings: the hooves start to differ; males’ arc width was significantly larger than females’.
• Adults: males’ hooves were significantly longer and wider than females’. The difference in arc width was highly significant, and the ranges of arc width for the two sexes barely overlapped.
• Overlap between the sexes means that a single set of tracks would not reveal the sex in most cases. However, the vast majority of adult males, and the larger yearling males, can be identified with a high degree of certainty.

3. What they concluded

• Hooves, and so tracks, of black-tailed deer differ by sex from the yearling stage onwards, mainly in width towards the front of the toe.
• Most adult males and the larger yearling males can be told from their tracks with a high degree of certainty, and these are the deer of greatest interest to hunters.
• Where deer live in heavy cover, as in western Oregon, researchers find far more tracks than deer, so even a little extra information from signs, such as the sex of some of the animals, is worthwhile.
• Broken and malformed hooves are often distinctive enough to recognise individual deer, and their use in following individual movements from tracks should not be overlooked.
• The results have not been tested on white-tailed deer or other mule deer subspecies, so applying them there is provisional. Limited field observations of Inyo mule deer tracks suggest they probably hold for that form.

4. How tracking was or was not used

The study grew out of the author’s own tracking: following fresh tracks to bedded deer in western Oregon and predicting their sex better than chance, and measuring tracks in Strawberry Canyon, where track width at one-third of the length back from the tip fell into two groups. The main study measured the hooves of dead deer rather than tracks, on the basis that hoof differences are reflected in the tracks. The author also briefly observed Inyo mule deer tracks in the field.

5. Tracker or observer certification

Not reported. The track observations were the author’s own, and his tracking skill is not described or tested. Three people are thanked for helping collect the hoof data.

6. Other technologies, skills or innovations

• A simple, repeatable hoof measurement, “arc width”, taken with a dial caliper by swinging an arc from the toe tip at one-third of the toe’s length. The same point on a track (one-third of the length back from the tip) was used in the earlier track measurements.
• Ageing deer by tooth replacement and wear.