Modification and dispersal of bones in a multi-scavenger environment
Petersen, Ariel Teresa Leigh
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Individuals left to decompose in outdoor environments may be subjected to all manner of carnivore scavenging before they are recovered. This study documents scavenging patterns to determine the effect of multiple species on human-sized pig (Sus scrofa) remains in an outdoor setting. It is hypothesized that that identification of the species involved in scavenging and postmortem damage to bone will correlate with patterns in the way skeletal elements are dispersed from the original point of deposition. Furthermore, the interactions of multiple species of scavengers modifying the same remains will impact the dispersal of skeletal elements differently than in studies documenting single scavenger taxa. The research was conducted on private land in the Yosemite Valley, CA, USA. Six pigs of comparable mass to adult humans were left exposed for five weeks beginning May 22, 2012, and observed daily for the first two weeks. After skeletonization, the bones were mapped, collected, and examined for carnivore modification. Two additional pigs were placed separately and left undisturbed for approximately six weeks, after which a thorough search of the area was undertaken to locate and map skeletal elements. Eighteen defleshed cow (Bos taurus) femora were also secured in the same outdoor environment to document scavenger gnaw marks and behavior. Six additional femora were given to domestic dogs (Canis familiaris) to document gnaw marks and behavior. Results of this study suggest that regular human interaction has an impact on carnivore behavior. During observational period of the study, carnivore activity was nonexistent. Once daily observations had ceased, within two days coyotes (Canis latrans) and wild pigs (Sus scrofa) began scavenging the remains. Coyotes and turkey vultures (Cathartes aura) scavenged the undisturbed pigs as early as two days after deposition, and complete disarticulation had occurred by the end of the six-week study. The cow femora were scavenged by turkey vultures and ravens (Corvus corax) daily regardless of human presence but were only scavenged by coyotes after daily observations had ceased. Analysis of dispersal patterns revealed that a majority of skeletal elements were found either adjacent to the original deposition site or along nearby game trails. This suggests following game trails is an effective technique for law enforcement attempting to locate remains. However, entire carcasses can be removed with minimal skeletal elements or soft tissue left behind, stressing the importance of detailed searches for small bones to establish the original site of deposition.
Thesis (M.S.)--Boston University