DEVELOPING TOOTH WEAR CRITERIA FOR AGING FREE-RANGING RANGIFER TARANDUS WITH COMPARISONS TO VISUAL ELEMENTS AND DISTANCE CALCULATIONS MADE AT TELESCOPIC SIGHT
The age of a harvested reindeer can be estimated from its teeth. These findings can be cross-checked with age estimates made before harvest while in the field. Age estimation is more accurate for younger age classes where tooth replacement is less subjective and more visible. Once reindeer attain permanent teeth, tooth wear is used to estimate age. A quick way to separate yearlings from adult reindeer is counting the peaks on the third premolar (Figs 12-13).1 Yearlings have three peaks on the third premolar while adult reindeer only have two. Tooth wear varies between individuals and can be difficult to interpret, particularly for reindeer older than 3 1⁄2 years.
• ReindeerFawn(<1year):Only four or five cheek teeth are showing. The third premolar has three cusps (Figs 14-15).
• 1 1⁄2 years: Six teeth are present on the lower jawbone. The third permanent molar may be (1) worn with a new tooth erupting underneath the gum, or (2) the new tooth has already erupted with two cusps (Figs 16-17). The last cusp of the third molar sits close to the gum line. The first three teeth (premolars) may look dull, but check the remaining three molars (fourth through sixth teeth) for sharp points. This is the sign of a young reindeer. (Sometimes worn premolars fool people into thinking the reindeer is older than it actually is.)
• 2 1⁄2 years: Because all permanent teeth have erupted by this age, aging older reindeer relies on comparing wear patterns observed for the lingual crest, enamel, and dentine (Fig. 18). For 2 1⁄2-year-old reindeer (Fig. 19), the first, second, and third premolars all have two cusps. The first molar is sharp and shows little or no wear. The last cusp of the third molar sits well above the gum line. Some wear may be visible on the last cusp.
• 3 1⁄2 years: On the first, second, and third molars, the lingual crests closest to the tongue show signs of wear (Fig. 20). Also, the last cusp of the third molar is flattened.
4 1⁄2 years: Teeth continue to wear for these older reindeer. The lingual crests closest to the tongue wear down with each passing year. The dentine (darker portions of the tooth) becomes thicker than the enamel (whiter portions of the tooth) (Fig. 21).
5 1⁄2 years and older: It becomes difficult to age reindeer as molars wear closer to the gum. Teeth become more cupped with age (Fig. 22).5
The aforementioned is a much more precise method of determining the age of reindeer near Noatak. The following are traditional procedure of identifying doe and fawn reindeer.
• Coloration: Some fawns born late in the breeding season may still have spots.
• Antler nubs:Thepediclesorantlerbasesofa “nubbin” or button buck are difficult to see. They become easier to see late in the hunting season, particularly from the side. Binoculars may be needed to see antler nubs.
• Head shape: A fawn’s forehead and snout (nose) are shorter than that of an adult doe. A doe’s head normally is more rounded on top between the ears. A buck fawn’s head is flattened by the presence of the pedicles. Look with binoculars for the pedicles or antler bases.
• Behavior: Fawns are more playful, naïve, and inquisitive than adults. Buck fawns tend to be aggressive. A buck fawn may be the first antlerless reindeer in a group to move into an opening.
• Body shape: The body of an adult doe is rectangular-shaped; a fawn’s body is shorter or even square-shaped. When side-by-side, the doe will be larger than the fawn.
• Wear and tear: Older bucks and does will have signs of aging, such as ears that appear too short for the head, a swayed back, and a sagging belly.
Full-grown reindeer near Kivalina and Noatak have the following physical characteristics, but notice that the designation of age is less precise than that of tooth wear criteria. These are subsequently an inferior rubric. Nevertheless, a reindeer’s physical appearance changes with maturity and can be used to estimate age. Does attain maximum body growth in 3 1⁄2 years, whereas a buck becomes full grown in 5 1⁄2 to 6 1⁄2 years.
• Immature Buck (1 1⁄2 to 3 1⁄2 years): Yearling bucks resemble a “doe with antlers.” These 1 1⁄2year bucks tend to have thin hindquarters and long, thin legs. They are like a teenage boy who has not reached full height or “filled in.” Yearlings are not as secretive as adults. Yearlings are often the first to enter food plots and tend to be in the vicinity of doe family groups. Their antlers are variable—anything from a spike to eight points. Regardless of the size and number of points, the antlers will be thin and spindly with a relatively narrow spread between antlers. The average size of a buck’s antlers doubles between 1 1⁄2 and 2 1⁄2 years of age. The 2 1⁄2 year olds appear similar to yearlings. Their racks are only about 60% of the size they will be at 51 1⁄2 to 6 1⁄2 years of age. A 3 1⁄2 year buck can be mistaken for a mature reindeer. The buck’s neck is thickly muscled during the rut, but the neck and shoulders are distinct from each other. They lack the body mass of an older buck. Their inside spread rack barely reaches outside the ears (Fig. 23). Their antlers are still only about 75% of their maximum growth.
• Middle-Aged Buck (4 1⁄2 to 6 1⁄2 Years): A 4 1⁄2 year buck has attained skeletal maturity. They display almost all the adult body mass expected to be seen in a fully mature reindeer. Their rumps appear full and rounded. During the rut, their neck is fully muscled and blends into the shoulders. Their waistline is as deep as the chest. Their stomach and back do not sag, and their jaw skin is tight. A 4 1⁄2 year old buck has achieved about 90 percent of his antler size in terms of number of points and inside spread (Fig. 24). A buck that is 5 1⁄2 to 6 1⁄2 years has achieved maximum antler growth. The beam circumference of the antlers continues to increase until the buck’s teeth wear down at > 7 1⁄2 years. During the rut, their neck blends completely into the shoulders. Their front half appears as one large mass. Their chest and body are thick, giving the illusion of shorter legs. Most exhibit squinty eyes and a sagging belly and back.
• Mature Buck (> 7 1⁄2 Years): Bucks older than 7 1⁄2 years often display a loss in muscle mass in the neck, a swayed back and a potbelly. Skin is loose on the neck and head areas. Some battle scars may be visible. Older bucks can be mistaken for younger animals because of their physical appearance. Their antlers degrade with advancing age.
Another inferior (but perhaps the most popular) system for quantifying the age is to observe characteristics of the reindeer’s antlers. Antler-size characteristics used in combination with body characteristics provide a good field estimate of a buck’s age. In general, antler growth increases with age until a buck approaches 6 or 7 years. Yearlings tend to have smaller antlers than mature reindeer. Antler characteristics, such as inside spread or number of points, can help identify yearling bucks, but antler growth can be highly variable among individual reindeer. Research near Kotzebue, Alaska indicates antler growth at 1 1⁄2 years of age does not predict antler development at maturity. A 1 1⁄2-year-old spike buck may exhibit eight or more points at maturity. In some populations, a mature reindeer buck’s antlers may never exceed eight points and a 15-inch inside spread. A combination of antler and body characteristics offers the best indications for estimating a reindeer’s age in the field, but it is still less precise than evaluating the reindeer’s tooth wear.
Finally, using a reindeer’s ears can provide rough estimates of antler dimensions to make age estimates:
• Width between ears: The width between a reindeer’s ears can be used to estimate the inside spread of antlers. When relaxed, the normal tip-to-tip distance between ears on a buck is about 15 inches. When the ears are pointed forward in an alarmed position, the tip-to-tip ear width is about 12 inches.
• Ear length: A mature reindeer buck’s ear is 6 to 7 inches from base to tip. Ear length can help estimate the length of an antler tine. Estimating beam length requires both front and side views. If the inside spread of the antler is > 15 inches and, from the side, the antler projects forward beyond the midpoint between the eyes and the tip of the nose, then the beam length likely exceeds 20 inches.
• Number of antler points: Antler points need to be viewed from various vantage points to be fully seen. Brow tines are easiest to see from the frontal position.