The taphonomic impact of scavenger guilds in peri-urban and rural regions of central and southern Alberta. Part I - Identification of forensically relevant vertebrate scavengers.

As a body decomposes in an outdoor environment, numerous taphonomic agents can act on the process of human decomposition. It is important to understand the impact of these agents as they can vary the rate of soft and hard tissue loss which may alter postmortem interval estimations. One taphonomic factor which has not been extensively investigated in many regions of the world, including Canada, are vertebrate scavengers. The current study aimed to identify scavenger guilds in the peri-urban and rural regions of two major cities in Alberta (Calgary and Edmonton) where human remains are frequently located. Vertebrate scavenger activity was recorded continuously using cellular and noncellular trail cameras. Images were analyzed to determine how the scavenging profiles (i.e., scavenger species, arrival time, and feeding behavior) impacted the loss of soft and hard tissue. We identified a range of mammalian and avian scavengers and found that coyote and black-billed magpie were the predominant scavengers recorded at the Edmonton peri-urban and rural sites, and the Calgary peri-urban sites. In contrast, when a site was within bear territory such as the Calgary rural sites, black and grizzly bears were the predominant scavengers. At all sites, the large mammalian scavengers were responsible for most soft tissue loss and subsequent hard tissue dispersal. None of the scavengers demonstrated a clear preference for open versus closed sites. This taphonomic information is important to consider when searching for human remains at these locations or in other North American regions with comparable scavenger guilds.

Scavenging activity can produce predictable patterns in surface skeletal remains scattering: observations and comments from two experiments.

In forensic contexts, surface deposited remains are frequently found that have been scattered by various taphonomic processes. In an effort to develop strategies to improve recovery rates, this study evaluates whether patterns can be detected in the scattering of remains due to scavenger activity. In two experiments, 24 human analogues (pig carcasses) were placed in two adjacent but differing environmental contexts: 12 in wooded and 12 in open grassland. Six carcasses in each of these contexts were dressed in human clothing. Elapsed time and direction of movement information for each carcass and its parts were collected and analyzed. Unclothed carcasses and carcasses in open contexts exhibited scavenger activity sooner than the others. Scattering of remains occurred along game trails and was directed away from human population and activity. Due to the highly variable nature of scavenger activity, daily observations during a research project are the key leading to a better understanding of the development of these patterns.