Story by Craig Nyhus, Lone Star Outdoor News
Most deer hunters have seen it. After a deer is taken, someone on the lease opens its mouth and sticks a finger in to rub the teeth. The per- son then looks up and says something like, “He’s four.”
Assessing a deer’s age by rubbing the molars along the back side of the deer’s mouth is an old technique, and many deer leases have plastic replicas to help get the feel of teeth at certain ages.
But is it accurate?
Researchers at the Caesar Kleberg Wildlife Research Institute examined the issue, which was presented at the recent Deer Research Meeting by Dr. Randy DeYoung, in a talk titled “Techniques for Aging Deer Based on Tooth Wear Aren’t Aging Well.”
“The technique was developed in the 1940s,” DeYoung said. “It follows the patterns of deer replacing baby teeth (at two years of age) with adult teeth, and then estimates the age by the amount the teeth are ground down by chewing. We teach it to our students.”
The study used deer on the King Ranch and examined more than 7,000 deer harvested from 2000-2014. The age was estimated by tooth wear and by Cementum Annuli (CA), a technique in which the tooth is extracted, sent to a lab, and “growth rings” are counted at the root of the tooth.
In comparing the estimates based on tooth wear to the CA method, researchers found some variation, but the estimates were within one year of each other more than 70 percent of the time.
DeYoung said this makes sense, since there are so many variables.
“We looked at the effect of clay soils versus sandy soils and the difference between a soft diet (including pelleted feed) versus a rough diet,” he said.
How accurate were the two techniques when the age of the deer was known?
Using information on 134 known-age deer from a study called the Buck Capture Project, teeth from deer older than two years when harvested were examined by six trained observers, and teeth were sent for CA aging at two labs.
The results of tooth wear examination were correct between 43 and 51 percent of the time, but 87 percent of the estimates were within one year of the actual age.
The CA results from the labs were correct 60 to 62 percent of the time, and 93 percent were within one year.
“The tooth wear examinations had a tendency to overage young deer and underage older deer,” DeYoung said. “The CA method was better for older deer. Both techniques are good for management, as they get within plus or minus 1 year most of the time.”
At the ranch, often the reply after the tooth wear test, is “He’s either 3 or 4.”
DeYoung provided a tip based on the results of the study to improve accuracy.
“If it’s a younger deer, go with the smaller number,” he said. “For an older deer, go with the higher number.”
Researcher also looked at some of the variables, including the effect of sandy soils, thinking the grit may increase tooth wear.
“There wasn’t much of a difference,” DeYoung said. “With ruminants like deer, it probably was washed off before the food was brought up to chew.”
What about supplemental feeding?
“It didn’t have much influence,” DeYoung said. “Deer still eat native forage.”
Other variables do have an impact, though.
“There was a lot of variation from the right to left side on the same deer,” DeYoung said. “Like humans, they chew mostly on one side. And some deer just have better teeth than others.”
With old deer, relying on tooth wear tends to go out the window.
“The variation is magnified in older deer,” DeYoung said. “With real old deer, people were aging at 6-7 and some of the deer were 8-10 and a few were 12.”
As a management tool, aging by tooth wear is helpful, DeYoung said, even though you might be off by a year.
“And after you shoot, it doesn’t matter what the teeth say,” he said. “He’s as old as he’s gonna get.”
