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GRANT: This deer is almost a decade old. And that is what makes this such a special evening for me.
GRANT: We stated that, Swoops, a buck I harvested recently, was ten years old. Now, we had pictures of Swoops since 2015 and he appeared mature at that time.
GRANT: However, on our social media, and on our episodes, we had a lot of questions about how old Swoops really was.
GRANT: In addition to his photographic record and our personal observations, a really good indicator, or way to estimate a buck’s age, is by looking at the wear and replacement technique of the teeth on the buck’s lower jaw.
GRANT: Knowing this, I was excited for Pete, my buddy and local taxidermist, to return Swoops’ head, including that lower jaw, have it all cleaned up, so I could really get a good look at those teeth.
GRANT: What I did not expect is for Pete to show me where Swoops had a lot of the upper jaw part of his skull missing.
GRANT: Pete explained that when he was skinning out the skull, there was a lot of rotten vegetative material kind of stuck up in the cheek. And that’s big evidence of a forage impaction, or what a lot of people call, lumpy jaw.
GRANT: Food impactions or lumpy jaw is caused by arterial worms. And these worms tend to live or congregate in the carotid arteries and then their larvae move on up to the capillaries in a deer’s head.
GRANT: The larvae can become so prominent that they actually block off these capillaries, causing nerves and muscles to die or not function in that area.
GRANT: The life cycle of these parasites is that the worms in the carotid arteries reproduce, horse flies bite the deer trying to get a blood meal, take some of those larvae in, the larvae advance in maturity, when the horse fly bites another deer to get a blood meal they can be transferred back to a deer.
GRANT: Again, in high populations, these larvae can restrict the blood flow to these facial capillaries, causing deer to almost have paralysis of those muscles.
GRANT: Due to the paralysis of these muscles and nerve damage, I doubt deer realize that they have a bunch of food stuck in their cheek between their, of course, cheek and their teeth. They don’t take their tongue and clean it out and it builds up over time.
GRANT: As with many injuries to deer, they’ll survive the injury just fine. It’s that secondary infection which causes them to die. And if deer leave that food in there for a long time, of course, it will rot and get really infected. And that infection can eat away on the bone or actually cause a massive infection throughout the deer to get systemic in the blood system and cause that deer to die.
GRANT: Swoops’ food impaction obviously was not that advanced. He looked healthy. He was a little run down from the rut. Based on trail camera pictures, he’d been going all over.
GRANT: But it was enough for that rotten vegetation to cause some erosion, or actually decay, of his upper jaw.
GRANT: Once I got past that shock, I was really ready to get that lower jaw and start estimating his age.
GRANT: The most common technique to estimate a deer’s age is the replacement and wear technique. Now, I was always taught the wear and replacement, and that rhymes a bit better. The deer actually replace teeth first, before much wear really happens.
GRANT: I want to stress that I say, estimate, because this technique is not 100% accurate. And I’ll explain why it’s not, later.
GRANT: And we don’t need 100% accuracy to manage most deer herds. Some research projects require more accuracy but as long as I know, you know, fawns, yearlings, young adults, more mature adults, I can prescribe a very good management plan.
GRANT: Using the replacement and wear technique, we know that fawns – well, you know, an older fawn, six-month-old fawn – will have about five teeth on that lower jaw. It would have three premolars or milk teeth, baby teeth we call them in humans. And a couple of molars that have erupted. That third molar, or the sixth tooth, hasn’t erupted yet, by its first birthday.
GRANT: By the deer’s second hunting season – the first hunting season was when it was a fawn, so a year and a half old deer, and 18-month-old deer – will have all six. Three premolars and three molars, on that lower jaw.
GRANT: While those molars are coming in there’s another even happening. Those premolars or milk teeth are going to be shed and replaced with a more permanent tooth. And this makes sense, of course, when a fawn is born that jaw is really small. And you need a small tooth and they’re feeding on milk and just learning to eat vegetation.
GRANT: But, as that deer matures, that jaw’s actually getting bigger, and you need a bigger tooth. It’s easier to produce another tooth, apparently, than for that tooth to expand.
GRANT: It’s easy to tell, when all those premolars have been replaced, because the third premolar, and we’re always counting from the mouth back towards the throat, so the third one back, it will shed out and that milk tooth will have three cusps. But it will be one tooth with three ridges or three little mountains on it. And it’s replaced with that adult premolar that only has two cusps.
GRANT: Now this was obvious from knowing Swoops, but a quick glance at his jaw, confirmed that he was two and a half years old or older. Because that third premolar only had two cusps.
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GRANT: Then next part of the replacement, the replacement’s over now, the wear technique is based on a really simple principle. And I’m going to illustrate it by talking about a chocolate ice cream cone. Don’t get this backwards. A chocolate cone dipped in vanilla.
GRANT: You see, the outside of a deer’s teeth, like human’s teeth, are covered in enamel. Kind of an off-white, really hard substance. But the inside is filled with dentine, a brown substance. And as a deer eats more over time, they wear off some of that enamel and more of the dentine shows. Just like a chocolate ice cream cone dipped in vanilla. The more you consume of that ice cream cone, the more of that center, the chocolate, shows.
GRANT: The angle of how that lower jaw meets the upper jaw results in, as a deer chews more, through time or there’s more wear on the teeth, that first molar is going to wear more. More of the inside dentine is going to show quicker than on the second molar or the third molar. Which works out perfectly, because about the end of that first year, after the deer has shed that premolar, you know, the milk tooth, and got the permanent premolar in, now we start looking at that wear and replacement. It takes about a year to wear through that first molar, again going from the nose to the throat or the fourth tooth back, three premolars and then the first molar, takes about a year for those cusps to wear, so, there’s as much brown, or dentine, showing as enamel.
GRANT: And the same follows suit. Another year goes by and on the second molar, or the fifth tooth back, you’re going to see about as much brown, or even more brown, than enamel. And if we go back up one towards the mouth, that first molar has even more dentine showing. So, you can see the way that jaw meets the skull, there’s more wear and tear on those front molars than the rear molar.
GRANT: So, at age three, four and five, that first, second and third molar start showing as much or more dentine than they do enamel.
GRANT: At age six, there’s so much wear, there’s still a lot of wear on that front molar, that those cusps have been worn off, those mountains have been worn off, and it’s kind of dished out. It’s level or dished out.
GRANT: And again, that follows suit. Year six, year seven, year eight, that first, second and third molar start getting dished out.
GRANT: At nine and ten, boy there’s a lot of gray room in here. But you’re going to see more dishing. It’s not just dished out. It’s flat. It’s worn way down. And you won’t even be able to see any of the enamel, or the light-colored material, in between the cusps. It’s just worn all the way down to where only dentine is showing.
GRANT: Now let me stop and say, this is not a class on how to use the wear and replacement technique, to accurately estimate the age of a deer. I’m just sharing about the technique, so we can really look at Swoops’ jawbone and confirm, he was very mature.
GRANT: When we look at Swoops’ jaw, those back molars are all dished out, worn way down, and it’s a whole lot of brown showing.
GRANT: Deer that live long enough and have chewed so much that all their molars are worn down, they’re just kind of flat – eight, nine, ten, 11, 12. Typically deer will get an absence when their teeth are that worn. They’ll get some food there in the gum line, just like humans, remember there’s – there’s no dental hygiene out there – that they’ll get an infection.
GRANT: I’ve seen where there’s been abscesses and a tooth missing out of a deer’s jaw. You know it’s got to be painful. In any case, Swoops was a very old deer, and our photographic record and our observations are supported by using replacement and wear technique, when we look at his jaw, that Swoops was ten years old, I’m going to say, plus or minus a year.
GRANT: Hunting season’s closing down or has closed in most states. And a lot of states have what’s called a DMAP, a deer assistance program, where the hunters or participants are required to turn in jawbones or accurate estimates of the age of the deer they harvested. This can be important for building life tables or recreating the harvest, so they can better estimate how to manage the herd or make good management plans.
GRANT: So, if you want to really get into how to age deer, there are all kind of great courses online. If you want even more accuracy, there’s a lab in Montana, called Matson’s Lab, and they actually created, many decades ago, the cementum annuli technique.
GRANT: Basically, they take an incisor, the little teeth at the front of a deer’s lower jaw; you pull it out, without damage to the tooth, send it in to them and they’ll cut, actually the root of that tooth, sand it, cut it with a microtine saw and sand it and put tetracycline on their, or another dye and count the rings of the teeth.
GRANT: Deer, of course, grow faster during the growing season, when there’s good groceries and slower in the winter. That’s true for most land mammals. And so, you can count the rings. You know, you get just like a tree ring, it’s going to be a lighter color, faster growing and then darker, denser material when there’s not as many groceries, in the winter, and give an even more accurate estimate of that deer’s age.
GRANT: The wear and replacement technique is really good for fawns, yearlings, and two-year-old’s. That can be really accurate. Once you start getting to three, four, five, six, it’s considered, and I agree with, that that cementum annuli, counting the rings, is more accurate to estimate the age of older deer.
GRANT: I don’t believe cementum annuli is necessary, unless you’re doing a detailed research project. But it’s really cool to have that data.
GRANT: You know, learning these things is a great way to enjoy Creation. But it’s even more important to be intentional to spend time, daily, seeking the Creator’s will for your life.
GRANT: Thanks for watching GrowingDeer.