Any hunter who has visited a Texas deer camp has seen it.
You know, the plaque on the wall with eight lower jawbones that allows hunters to gauge a recently harvested deer’s age.
According to a group of South Texas biologists, those plaques were iffy at best, and frequently downright wrong.
The group of biologists, headed by Dr. Susan Cooper, of the Texas AgriLife Research and Extension Center in Uvalde, has devised a new way to age deer using one tooth instead of the whole jawbone.
“Everyone uses the old tooth wear, but we know that is not very accurate,” Cooper said. “Landowners want something better, and I had a teacher’s assistant suggest looking at one tooth.”
The new method examines the width of the dentine — the hard tissue located under the enamel of a tooth — in this case, the first bicuspid molar. In plain English, the third tooth of the lower jawbone.
“It came out that that was the only thing related to age,” Cooper said.
After discussion and evaluation, the team determined the first permanent molar would be the tooth that was most likely to show age-related wear patterns.
Using digital calipers, they took accurate measurements in millimeters of tooth height, as well as all ridges of white enamel and brown dentine on the tooth from jaw samples of harvested known-age bucks 2.5 to 7.5 years old.
“We wanted to see if we could go to just one location in the jaw to reduce the amount of variability of age-related wear within the jaw,” said research assistant Shane Sieckenius. “This particular tooth was consistent in showing the true indication of wear.”
Cooper said the original aging method, known as the Severinghaus technique, was developed using deer from New York and is inaccurate for estimating the age of deer in Texas beyond the rough categorizations of young, mature or old.
“You can pretty much look at a deer and tell if it is young, mature or old,” Cooper said. “The old technique was originally used to establish age in winter killed deer in New York. It was never designed to age deer in Texas.”
Cooper said over the past 10 years the wildlife team at the Uvalde center has ear-tagged more than 2,000 wild buck fawns on South Texas ranches. During that time, ranch owners and operators kept tabs on ear-tagged deer, collaborating with the center on deer-related research.
“When these bucks are harvested, the partner ranch returns any known-age jawbones from tagged deer to us for evaluation and assessment,” she said.
Cooper said when tested on a sample of jaws from 141 bucks, the formula predicted the correct age for 61 percent of young bucks aged 2.5 to 3.5 years; 53 percent of mature bucks aged 4.5 to 6.5 years, and 25 percent of old bucks aged 7.5 to 8.5 years.
All of the deer were correctly aged within a year of their actual age. Those numbers are nearly double the accuracy of the old method, Cooper said.
The new method only works in bucks, because bucks will draw calcium from their bodies to grow horns, while does won’t, thus changing the equation to find an accurate age.
“This (new method) allows those that deal with deer to get a more accurate age,” Cooper said.