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Tooth Impression Analysis On Predator Killed Elk

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reprinted with permission  5/4/2020



Tooth Impression Analysis On Predator Killed Elk

By Gerald Mills, BS Wildlife Biology and Aaron Mills, BS, with Mitchel Townsend, MA, contributing


NOVEMBER 1, 2014




The bone tooth impression analysis of two predator killed elk located 10 miles apart in the Gifford Pinchot National Forest, east of Mt. St. Helens, and a couple deer kills seven miles to the northwest of there. Elk kill number 1 (EK#1) was an adult cow elk, discovered on 8-23-14 by Gerald Mills and Aaron Mills at the bottom of an old clear-cut. The bones were stacked by the predator as the flesh was eaten off of them. The bones in the pile were rib bones and vertebrae. Three bones were initially collected at this site. With a later visit to the site on 10-31-14, two more bones were found to have teeth impressions and were also collected.

The second elk kill (EK#2) was found by Gerald Mills, while elk hunting with Tom Treichel, on 9-8-14, also in an old clear-cut, about 10 miles SE of EK#1. This was also an adult cow elk. Three rib bones were collected from this site. The rib bones were stacked on top of a clump of bear grass.

Since the type of predator, which has feasted on the kill, can be determined by the tooth impressions left on the bones (Murman et al. 2006; Foust. 2010), it was decided to do a study of the bones to determine said predator.

Also included in this analysis is the bone stack (BP#1) discovered by Mitchel Townsend in the spring of 2013, north of Mt. St. Helens. This location is about 7 miles NW of EK#1. This is an excerpt from Mr. Townsends discovery narrative:

After taking some initial pictures and video I did a physical examination of the site contents and discovered that at least two sets of deer remains based upon the deer skulls found in direct proximity to the main pile of bones. The skulls had their noses/snouts crushed by what looked like blunt force trauma and had been placed in the same nose downhill orientation. This seemed odd at first glance. What really caught my eye was a pile of bones next to a small log. My first impression was that something or someone had sat down and consumed these animals and just dropped the bones between their legs as they finished them. I further confirmed this by looking closely at the stack and noted some interesting observations.

The bones seemed to be mostly rib bones that showed evidence of teeth marks and mechanical manipulation to varying degrees. Some areas had seemingly been bitten out and discernible dental impressions left behind. These dental impressions looked measurably different from the other known species that inhabit this ecosystem. After a few more photographs and sustained reflection I decided to collect the best sample of the deer bones from the “Bone Stack”.

What resident animal species would kill deer with blunt force trauma on the head, position them in the same directional orientation, eat the animals and drop the bones in a pile? How come scavengers were avoiding this site even though some of the bones still had flesh attached? These were just some of the questions now rushing through my thoughts.



Most of the impressions were on the edges of the bone so we could only measure the width of the tooth. Only on one impression were we able to measure the thickness of the tooth as noted below. We assigned each elk kill a number 1 or 2. We then assigned each bone a letter and number designation; i.e. RB1, RB for rib bone and V for vertebrae. Then a number was assigned for the impression location and finally a mark, for the individual impressions, numbered from left to right. So it looks like this EK#1 RB1-1 mark 1. The places where two canine impressions could be discerned, we also measured the distance from center to center of the canine pits. We were also able to calculate a bite radius in several places by marking the center of each impression on a piece of paper then using a compass to draw an arc of the impressions and determine the radius of the tooth impressions. For a comparison Gerald also measured his bite radius and called it Reference Bite Radius. Tooth impression data is compiled into Table 1.

Tools: Mitutoyo Dial calipers in inches (millimeters in parenthesis). The bite radius was determined by finding the center of each impression and measuring the distance from the edge of the bone. These measurements were then placed into a CAD X11 2D drafting program to create an arc from which the bite radius could be determined. (I’m sorry about mentioning the two ways we measured the bite radius. But, we actually used both, with the graphic software being more accurate.)


Measurements and observations:

(Note: pictures of each of these described locations can be found in Appendix 2 on pages 16 - 23.)


Found ??-??-13, Collected bones: 4 rib bones. Designations: RB1, RB2, RB3, RB4
8 lower foot bones
2 wrist or ankle bones
1 toe bone
2 halves of one hoof

RB1: The ventral end is broken. Possible rounded molar cusp impressions at break on inside. One flat incisor impression on side of rib near dorsal end .50” (12.7mm) wide. No other modifications to bone.
RB2: One flat incisor impression on side of rib near dorsal end .50” (12.7mm) wide. No other modifications to bone.
RB3: One flat incisor impression on side of rib near dorsal end .54” (13.72mm) wide. No other modifications to bone.
RB4: The bone is broken diagonally at the ventral end, it is very slightly jagged on the inside edge. There is a rough spot on the dorsal end of the bone that may have occurred when the bone was disarticulated from the spine.

The rest of the bones collected show no modification or scoring by teeth. Most of the flesh and all the cartilage has been removed from the bones. All these bones were disarticulated but none were cracked or chewed hard enough to leave any impressions.


Found 8-23-14

Collected bones: 4 rib bones. Designations: RB1, RB2, RB3, RB4
1 vertebra. Designated: V1

V1: Has one mark at the dorsal tip approximately .11” (2.79mm) dia. It appears to be from a canine of a small animal. No other apparent marks.

RB1: The ventral end is broken. It appears to have been chewed off. There are no identifiable teeth marks here. There are five distinct bite mark locations on the sides of the rib and one indistinct mark.

RB1-1: Appears to be made by 3 large flats incisors.

Mark 1 is .75” (19.05mm) wide.
Mark 2 is .61” (15.49mm) wide.
Mark 3 is .62” (15.75mm) wide approximately, it’s hard to tell because it looks like the bone split off here.



Fig. 1: Shows the bite radius for RB1-1 Marks 1, 2, 3, taken from

the bone impressions. (41.91mm)



Fig. 2: Gerald’s bite radius for a reference comparison. (19.05mm)



RB1-2: Shows one incisor impression on the outside and two impressions on the inside of the rib. It bit through but didn’t break the piece off. The one tooth that went through measures .55” (13.97mm) wide x .15” (3.81mm) thick. The bone may have flexed around the tooth here and sprung back making an exact measurement of the tooth impression not possible.

RB1-3: Shows the same flat tooth form, but of a smaller size. The slight impressions of mamelons can be seen here which is a juvenile human trait. (Chegini-Ferehini S, Fuss J, Townsend G. 2000.)

Mark 1 barely grazed the bone at .21” (5.33mm) wide.
Mark 2 is .3125” (7.94mm) wide.
Mark 3 is .40” (10.16mm) wide.



Fig. 3: Shows the bite radius for RB1-3 Marks 1, 2, 3,

taken from the bone impressions. (30.48mm)


RB1-4 The bone is chipped with no apparent teeth marks.
RB1-5 There is a 1” (25.4mm) long chunk out of the bone here but it was hard to determine whether it was the smaller or larger teeth which made this mark.

RB1-6 There are marks that appear to have been made by rounded molar cusps. They are very shallow dents.


RB2: Is chewed or broken off similar to RB1. There is one gouge on one side which shows no pointed tooth marks. On the opposite side there is a thin long chip out of the rib which measures .55” (13.97mm) long.

RB3: Is gnawed at the ventral end. There may by wide flat cusp marks or it may be the way the bone broke.


RB3-1 On one side a couple of flat incisor marks are apparent.

Mark 1 is .38” (9.65mm) wide.
Mark 2 is .40” (10.16mm) wide.

RB3-2 Opposite RB3-1 there is a 1.75” (44.45mm) long piece of bone missing with a possible impression of a flat tooth with no sharp cusp marks.
RB3-3 There is a 1.8” (45.72mm) long edge missing. On the inside of the bone in this area are two flat impressions .28” (7.11mm) long.


RB4: Both the dorsal and ventral ends of the bone have been gnawed on.


RB4-1 One flat incisor mark .37” (9.4mm) wide.
RB4-2 Two flat incisor impressions in bone.

Mark 1 is .27” (6.56mm) wide.
Mark 2 is .29” (7.37mm) wide.

Note: These marks were made by the smaller set of incisors. Take special note of RB4-2, you can see the mamelons on the ends of the incisors imprinted here. (Chegini-Ferehini S, Fuss J, Townsend G. 2000.)


RB4-3 The dorsal end of the bone has 2 canine impressions .125” (3.18mm) dia. and .325” (8.26mm) on centers.



Found 9-8-14

Collected bones: 3 rib bones. Designations: RB1, RB2, RB3.

RB1 The dorsal end shows no damage or modifications. We noted the edge of the rib bone above the writing has shallow flat impressions when you run your finger longitudinally along the bone. As if a flat tooth was used along the bone to remove the flesh. The ventral end of the bone shows modification by a small predator/scavenger with sharp molars or canines.


RB1-1 Appears to have been made by three flat incisors.

Mark 1 is .42” (10.67mm) wide.
Mark 2 is .47” (11.94mm) wide.
Mark 3 is .48” (12.19mm) wide.


RB1-2 On the dorsal end are teeth marks made by a small predator/scavenger. The bone appears to have been bitten from the internal side with the maxillary incisors.

Maxillary canine width is .25” (6.35mm). Distance apart .525”(13.34mm).
Mandibular canine width .125” (3.18mm). Distance apart .35” (8.89mm).


RB1-3 Two slight impressions which match the distance between the maxillary incisors of RB2-2 at .525” (13.34mm) are visible about 4.5” (114.3mm) from the end of the bone on the external side.

RB1-4 There is a long score on the internal side of the bone opposite RB1-1 which is 1.25” (31.75mm) long. It appears to be pressed into rather than scribed along the bone as there are slight tooth impressions on the opposite side, biting down on, rather than sliding along the rib bone.

RB2 Shows modification by at least two different predator/scavengers; the head is gone and the ventral end shows tooth scoring.


RB2-1 Shows three distinct flat tooth marks.

Mark 1 is .62” (15.75mm) wide.
Mark 2 is .49” (12.45mm) wide. This impression shows a distinct twist to the tooth. It is out of line with the rest of the teeth. This may be a peculiarity to this animal and may help identify it from others if more kills are found. We dubbed it Snagtooth.
Mark 3 is .46” (11.68mm) wide.



Fig. 4: Shows the bite radius for RB2-1 Marks 1, 2, 3, taken from the

bone impressions (37.08mm). It was difficult to get an exact radius of

the bite because of the twisted tooth.


RB2-2 This mark shows a straight impression toward the bone median before the tooth moved back and bit a piece out of the bone.

Mark 1 is a .4” (10.16mm) long impression.
Mark 2 is a .73” (18.54mm) wide gouge out of the bone.


RB2-3 Same type of impression as RB2-2. It bit down then moved back, but this time the second bite missed the bone.

Mark 1 is a .4” (10.16mm) long impression.


RB2-4&5 Both ends of the bone are gnawed on. They show sharp impressions such as a molar of a small predator/scavenger.


RB2-6 Shows the canine marks of a small predator/scavenger.

Maxillary canine width is .17” (4.32mm). Distance apart .475”(12.07mm).
Mandibular canine width is .17” (4.32mm). Distance apart .35” (10.16mm).


RB2-7 Shows the same impressions as RB2-6 but with additional score marks from the median to the outer edge of the bone.
RB2-8 Three light scores are visible in the center of the bone parallel to the axis approximately 1.1” (27.94mm) to 2.6” (66.04mm) long, .21” (5.33mm) equidistant apart.


RB3 Has several impressions along one edge where a small predator/scavenger was gnawing on the bone. The cusp impressions are of a triangular form .1” (2.54mm) wide. A section of the bone is missing here 2.5” (63.5mm) long. There may be some flat incisor marks here. If I overlay RB2-2 with this area it is a good match with RB2-2 marks 2 & 3, mark 2 being the snagtooth. The smaller scavenger may have gnawed this area after these marks were made.


Size ranges for human-like incisor impressions in found bones: Width ranges of the larger incisor-like impressions measured .42” -.75” (10.67-19.05mm) wide. The smaller incisor-like impressions in EK#1 RB1 measured .21” -.40” (5.33-10.16mm) wide. We did not try to differentiate between central and lateral incisors.

Human incisor size comparisons: This information was gathered from a study done by Magne et al. 2003, from The Journal of Prosthetic Dentistry. These size ranges were taken from 44 central incisors and 41 lateral incisors of extracted human maxillary anterior teeth. The unworn central incisor range was .33”-.44” (8.46-11.07mm) wide; while the unworn lateral incisor range was .22”-.32” (5.51-8.22mm) wide.


Table 1: Measurements of tooth impressions in bones


Footnote (a) Refer to the Measurements and Observations section for

a description of the impression in this location.


Table 2 shows a comparison between the two most likely predators in SW Washington; the black bear and the cougar; a well as the wolf and the grizzly just for further comparison. These measurements were from the study done by Murman et al. (2006) and Foust (2010). The mean width of each canine and the mean distance between (DB) them at their bases is included in the table; as well as the width of the three larger impressions measured together from EK#1 and EK#2. The measurements are in millimeters in this table. Also note that predator canines have a round or oval cross section. We must consider if these are the incisor marks of one of these predators they must fit between the canines.


Table 2



Please note that there are only three impressions registered on these rib bones. The impression width for the elk kills is the total width of all three tooth impressions. If the predator is human-like there would be four incisors. If it is one of the predators mentioned here, there would be six incisors (Skelton. 2011). This being the case these teeth will not fit between the above mentioned predators’ canines.



Major bone modifications were made by an unknown predator and the bones were stacked after eating the flesh from the bones. Skelton, in his book, A Survey of the Forensic Sciences, makes a statement about determining what caused a bite mark:

The bite of a carnivore can usually be distinguished from the bite of a human by comparing the sizes of the incisor and cuspid teeth. Cuspids in non-humans are called canine teeth. Carnivores, such as dogs, bears, and mountain lions have small incisors and large canines. Therefore their bites usually consist of two deep punctures with six small indentions in between, which correspond to the three incisors per quadrant of most carnivores. In humans, however, the cuspids are relatively small and the incisors are relatively large, especially the first incisors. So, a human bite will usually consist of two broad tears or punctures in the center of the mark, corresponding to the two first incisors; with two smaller indentations on each side corresponding to the second incisors and the cuspids. (Skelton. 2011)


The impressions were made by large flat incisor-like teeth; human-like in appearance except for the size. These teeth didn’t cause the usual pits and score marks made by other known predators as determined in studies by Murman et al. (2006) and Foust (2010). The scores and pits that were caused by the usual predator type teeth were all smaller than a domestic cat per the above mentioned studies. These smaller marks were made by small secondary predator/scavengers, which are not large enough to kill a mature cow elk or a deer.

There was little damage to the majority of the dorsal ends of the rib bones, as would normally be evident on most predator kills; even though the bones had been disarticulated and stacked. The damage that was noted was apparently done, either during the process of disarticulation, or by secondary scavengers, since the teeth impressions in these areas were from smaller animals.

The method of killing these two elk is not known. However, it was noted that the nasal area of the skull of EK#1 was crushed; as were the skulls of BP#1. The EK#2 skull was intact; however, the spinal column was in two pieces. It is not known if this occurred at the time of the kill or some time afterwards.

It is concluded there were three distinct individuals, with possibly a fourth evidenced by the deer kills and two elk kills located about 17 miles apart from each other in a straight line. This conclusion was arrived at by measuring tooth impression width and juxtaposition. In EK#1 there were two different size impressions of flat incisors. The inference being that there was an adult and a juvenile. On EK#2 there were three tooth impressions together as in EK#1; however, one of the three marks showed a marked deviation from the axis of the other two marks. BP#1 didn’t show enough modification evidence to conclude a fourth individual although the impressions were all in the same size range as EK#2 but did not show the snagtooth orientation.


Rodent gnawing can be ruled out as a cause of the impressions on the bones. One, because of the size of the marks and, two, because there are three impressions together in several locations on the bones; a rodent would have to take two bites to do this. Also, rodents leave a score mark as they are gnawing. This was noted on some of the older elk kills found, but not on these two or the deer kills.

The conclusion is these kills were the result of a large unknown predator which stacks the bones while feeding on its kill. In this part of the country the only known predators large enough to kill a mature elk are cougars and black bears. Both of which will kill calves before taking on a mature elk. The percentage of cougars killing mature elk is very low per Clark (2014). No cougar or bear modifications were found on these two elk kills and they do not stack the bones while feeding.



References Cited:
Clark, Darren A. 2014. Implications of Cougar Prey Selection and Demography on Population Dynamics of Elk in Northeastern Oregon. Doctoral Dissertation. Oregon State University.
Chegini-Ferehini S, Fuss J, Townsend G. 2000. Intra- and Inter-population Variability
In Mamelon Expression on Incisor Teeth. Dental Anthropology Volume 14, Number 3, 2000.
Foust, Jennifer L. 2007. The Use of Tooth Pit and Tooth/Jaw Measurements to Identify Carnivore Taxa Responsible for Damage on Scavenged Bone. Master of Arts Thesis. University of Montana.
Magne P, Gallucci GO, Beler UC. 2003. Anatomic crown width/length ratios of unworn and worn maxillary teeth in white subjects. The Journal of Prosthetic Dentistry 89(5):453-461.
Murmann DC, Brumit PC, Schrader BA, Senn DR. 2006. A Comparison of Animal Jaws and Bite Mark Patterns. Journal of Forensic Science 51(4):846-860.
Skelton, Randall R. 2011. A Survey of the Forensic Sciences. Lulu.com. Section 28.3.1 pg 313.
Further Reading References:
Carson EA, Stefan VH, Powell JF. 2000. Skeletal Manifestations of Bear Scavenging. Journal of Forensic Sciences 45(3):515-526
Haglund WD, Reay DT, Swindler DR. 1989. Canid scavenging/disarticulation sequence of human remains in the Pacific Northwest. Journal of Forensic Sciences 34(3):587-606.
Haglund WD. 1992. Rodents and human remains. Journal of Forensic Sciences 37:1459-1465.



Appendix 1:

Additional information:
The bones of BP#1 were stacked together in a pile. The rib bones of both EK#1 and EK#2 were also stacked together in piles. The bone stacking appeared to be feeding behavior where the animal simply sat in one place and put the bones in a stack in front of it as it fed. We estimate that both elk kills were done in the spring of this year. When examining the area around EK#1, a hunter killed elk was discovered about 40 yards behind it; this was apparent from the saw marks on the leg bones and the pelvis. It was a couple of years old. These bones were also scattered about with small predator/scavenger marks and rodent tooth marks on the bones; no bone piles.

When early season archery elk hunting in September we killed an elk. We used this for a control specimen. See appendix 3.

Additional Observation:
On 8-23-14, the same day EK#1 was found, we found a track-way of large tracks. We estimated the tracks had been made in the previous week and a half; since a thunderstorm had occurred in that time and it had rained. The tracks were 16” long x 7” across the ball x 4.5” across the heel. We were able to cast one of the tracks. We found that the step was 72” and the stride 144”. We were able to back track the animal about 100 yards through the big timber back to near the Boundary Trail #1. It looked as if someone on the trail had spooked the animal and it ran up the hill across the skidder road where we found the tracks. We don’t know if this has any connection with the EK#1, however it was within 500 yards.



Appendix 2:


BP#1 Stack of Bones



BP#1 Bones Collected



BP#1 RB1



BP#1 RB2




BP#1 RB3




BP#1 RB4




EK#1 Bone pile and skull.





EK#1 Bones Collected



EK#1 RB1




EK#1 RB1





EK#1 RB2





EK#1 RB3





EK#1 RB4





EK#2 Bone pile, skull and vertebrae.





EK#2 Collected Bones





EK#2 RB1





EK#2 RB2





EK#2 RB3





Appendix 3:

Control Specimen
This elk was killed by my hunting partner during early archery season in September 2014. It was a 4x5 bull (antler point count). At that time we quartered it and deboned the rest. We left the rib cage and spine all attached. I didn't decide to use this as a control specimen until a couple months later. I would have done things differently from the start if I had decided this earlier. I should have taken a picture as we left it after our task of quartering and boning the elk. I should have placed a game camera to log the animals which visited the site.

These are the author’s observations and pictures of this site over a period of 6 months or so. These observations are specifically for the maritime Pacific Northwest. Sometimes it snows in the winter, sometimes it doesn't. This last winter it didn't. Cold weather will preserve kills and make them look newer than they actually are. Usually it rains until mid to late June. Then it quits and dries out until about mid-September. Sometimes we have beautiful Indian summers clear into late October. Keeping these factors in mind you can determine a possible age for a kill. The two elk kills #1 and #2 had dry flesh remaining on some of the bones. It looked jerky like. The flesh hadn't been exposed to extended periods of rainfall which turns flesh white. The bone will also exhibit a green or orange patina from algae if it over winters. The bones were still white. Therefore, the kills probably happened in June or after of 2014.

We can now look at the control specimen and witness what happened to it over the last 6 months. We were back in the control area hunting about 2 days after the kill was made. When we arrived at the site no animals were seen in the vicinity of the carcass. However, in the flesh and hide that remained was the impression of a large canine. Something had drug the carcass about 30 feet from the gut pile, which was still intact. I interpreted this as being a cougar. A bear probably would have attacked the gut pile first. There were no visible tracks in the vicinity.

Now we get to the pictures I did take at the end of October, about a month and a half later. At this time the gut pile was totally gone and the hide was nothing but hair on the ground. The possible cougar had managed to drag the carcass about 30 yards from the original spot. We could tell this by the hair left in that spot. But that wasn't the final resting place. Something had dragged the bones back about 20 yards to the other side of the of where they had originally rested. So about 50 yards in all from where it had been dragged first. Looking at the pictures you can see most of the rib bones are still attached, except for the ones that had rubbed on the ground during the process of being dragged. Also, along the edge of the ribs you can see the small crenulations made by the predators' incisors. Note, there are no noticeable impressions in the bones themselves. Also, note the white flesh still attached where the ribs meet the spine. It has been rained on for an extended period of time.



The elk we killed in September during archery season, photos taken in October.




These pictures were taken in February of 2015, about 6 months after the elk had been killed. Natural disarticulation has finally occurred through decay and we end up with what looks like a bone stack. At this point a question arises, when did the disarticulation occur? If the bones haven't been disturbed, you might be able to tell by their orientation to each other. However, if they have been disturbed, then the only other way to tell is to look for impressions on the bones themselves. Notice the color of the bone has changed.





After I discovered how important it could be to check out any bones. I found more cow elk bones just down the road from our hunting camp last year (2014). The skull was there. The rest of the bones were scattered around the area. I could find no impressions in the bones. I came to the conclusion that it was cougar killed, wounded by a hunter, or just died of natural causes. If a deer or elk was killed by a hunter and boned in the field. You will probably find saw marks on the lower leg bones and pelvis. This evidence is present on our control specimen. We also found some older bones about 50 yards behind EK #1 that showed saw marks in the above mentioned bones.


I have given some thought to this disarticulation while feeding. When we eat a rack of ribs, we pull them apart. The shape of our faces won't allow us to remove the flesh between the ribs without doing so. If we find a skeleton with the ribs still attached, then it was probably a carnivore (of the Order Carnivora) that fed on the kill.


Appendix 4:

These photos from Skulls Unlimited International, Inc. are provided for a visual comparison between the incisors of the order Carnivora and the order Primate.



                 Various Carnivores (skullsunlimited.com)                                                         Various Primates (skullsunlimited.com)





Black Bear, Ursus americanus (skullsunlimited.com)                                          Mountain Lion, Felis concolor (skullsunlimited.com)




Bonobo, Pan paniscus (skullsunlimited.com)                                                Chimpanzee, Pan troglodytes(skullsunlimited.com)






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