Guest post by Christine Hymanyk
(See Scattered, Ep 10 for my chat with Christine about her research project.)
My animal scavenging experiment was inspired by several existing studies, some of which I have listed for further reading at the end of this post. My stated purpose was to collect samples of cow rib bone that had been chewed by a wild canid (a coyote, in this case) to compare to the appearance of a bone that had been chewed by a domestic dog. Based on what I read, I hypothesized that the domestic or captive dogs in my experiment would be more prone to excessive gnawing of bones over their wild relatives, most likely due to boredom or a lack of security at the scavenging site. By the end of the experiment, I hoped to be able to retrieve a bone that showed only canine tooth marks, which could then be observed and contrasted to my dog-chewed samples to test if my hypothesis was correct or not.
There were several challenges to reaching this outcome, which I did my best to take into consideration or plan around in advance. Attempting to control or otherwise create a significant impact on the actions of the wild animals was something I wanted to avoid wherever possible, but at the same time, I also wanted to minimize the chances that scavengers would be able to easily carry the bones away. To do this, I made sure that when I left the bones at the experiment site, they were tightly tied onto ropes and then tied to a sturdy tree. Another problem lay in the uncertainty that any bones recovered would be scavenged by coyotes specifically, so I made use of a trail camera which was set to take pictures at specific intervals when it detected movement. This would allow me to confirm which animals, if any, had been chewing on the bones.
Once the setup was complete, my part was comparatively easy—all I had to do was sit back, relax, and wait to see if any scavengers took notice.
To my surprise and excitement, it didn’t take long to see activity. Over the course of the experiment, the site was visited by a variety of animals including coyotes, magpies, deer, a fisher (Figure 1), a moose, and even a black bear (Figure 2).
It soon became clear, however, that an unexpected downside of this level of activity is that even after being carefully tied down the bones were still removed from the site quite efficiently, which made retrieving a tooth-marked bone for study difficult. Even after running the experiment 3 times and setting out fresh bones in each case, I only managed to retrieve a single scavenged bone (shown here, Figure 3).
What is also unfortunate for the initial goal of my experiment is that pictures from the trail camera indicated that the bone retrieved from the experiment site was only scavenged by magpies, with no coyote activity to speak of. This made it difficult to follow up on my original hypothesis involving the scavenging habits of wild vs. domestic canids, although some comparison was still possible. It is apparent that the magpie-scavenged bone shows much less modification than that of the domestic dog. It lacks the dramatic punctures caused by teeth, as most of the scavenging efforts of the magpies seems to have been put toward picking off any flesh and cartilage left on the bone, resulting in a pitted appearance that became very difficult to detect once the bone had been cleaned. The bone chewed by the domestic dog, in contrast, shows large portions of the bone itself having been broken off and devoured (Figure 4). It is also worth noting that in the case of the dog-chewed bone, the bone itself was being eaten even before the attached meat had been completely removed, possibly indicating that the dog was chewing the bone more as a form of recreation than as a food source. It might also indicate that the dog, who was given the bone at home, felt secure enough to take its time with it.
While the original goal of the experiment was not reached this time, the results of this experiment do reveal some opportunities to potentially take the study further. What more can be learned about scavenger behaviour from photos? Were the herbivores at the site active scavengers or there by coincidence? Would repeating the experiment at a different time of year have any effect on the number and variety of animals observed? If a whole animal corpse were to be set out, could we witness different animals’ methods of disarticulating and scavenging a corpse? One of the chief advantages of this experiment lies in the easy replicability of its design, as it is simple, inexpensive and may be set up as many times as needed. Given the unpredictability of animal behaviour, the differing results gathered in each new test have the potential to lend a wide range of new insights into the processes and appearances of animal scavenging on bone.
Binford, L. R. (1981). “Chapter 3: Patterns of Bone Modifications Produced by Nonhuman Agents” in Bones: ancient men and modern myths. Academic Press, 35-86.
Carson, E. A., Stefan, V. H., and Powell, J. F. (2000). Skeletal manifestations of bear scavenging. Journal of Forensic Sciences, 45(3), 515-526.
Haglund, W. D., Reay, D. T. and Swindler, D. R. (1989). Canid scavenging/disarticulation sequence of human remains in the Pacific Northwest. Journal of Forensic Sciences, 34(3), 587-606.
Sala, N. Arsuaga, J. L., and Haynes, G. (2014). Taphonomic comparison of bone modifications caused by wild and captive wolves (Canis lupus). Quaternary International, 330, 126-135.
Ubelaker, D.H. and DeGaglia, C.M. (2019). The impact of scavenging: perspective from casework in forensic anthropology, Forensic Sciences Research, 5:1, 32-37, DOI: 10.1080/20961790.2019.1704473
Leave a Reply