The Effects of Clothing on Vulture Scavenging and Spatial Distribution of Human Remains in Central Texas
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Vultures and other animal scavengers have the ability to feed on human remains, which can lead to rapid tissue loss as well as movement of body parts over time. This can lead to misinterpretations of the scene and incomplete recovery of evidence. What is not known, however, is how clothing may affect how vultures feed on human remains and in turn how that may affect the spatial distribution of the remains. This thesis seeks to explore the effects of clothing on vulture scavenging and spatial distribution of human remains in Central Texas.
Five donated human subjects were dressed in a white t-shirt, blue jeans, socks, and tennis shoes prior to placement at the Forensic Anthropology Research Facility (FARF) at Texas State University. Upon placement, traditional baseline measurements were made to document the placement area and compare to final positions. A drone flew over to capture aerial photographs. During the data collection period for each individual, visual observations, notes, digital photography, and game cameras were used to monitor the subjects. Once the observation period was over for each individual, baseline measurements were taken again in order to document where the scavenged remains were dispersed. The study period refers to the observation time from placement until final data collection. All data for clothed individuals was compared to subjects from past vulture studies using unclothed human subjects. Statistical differences in average feeding times were analyzed using a Welch’s t-test. All baseline measurements were plotted on scatter plots with different colored polygons drawn around each scatter (placement and final) for each clothed individual. GPS data from the unclothed subjects were exported into Google Earth Pro, where polygons were also drawn around each scatter for each unclothed individual. Area was calculated for these polygons within Google Earth. In order to assess postmortem interval (PMI) estimations, weather data was collected and known accumulated degree days (ADD) was calculated for each individual. Total Body Score (TBS) was then assessed for each individual using the Megyesi et al. (2005) method. Estimated ADD was also calculated for each individual using this method. Inaccuracy and bias were then determined for each individual in order to compare known and estimated ADD. Spearman’s rank test and t-test further provided information regarding the utility of this method.
Results of this study were presented in terms of feeding pattern/duration, spatial distribution, and ADD/PMI estimations. The differences in feeding pattern and duration between clothed and unclothed remains were determined to be statistically non- significant. Further, the differences in spatial distribution between clothed and unclothed remains were also determined to be non-significant. Though there were no statistically significant differences in these areas of the study, some useful information could be extracted from the results. Comparisons of known ADD to estimated ADD calculated via the Megyesi et al. (2005) method showed that this method consistently overestimated the PMI of the clothed, vulture-scavenged subjects. There was also a correlation between the inaccuracy of the estimated ADD and length of time vultures fed: the longer vultures fed on a subject, the more inaccurate the ADD/PMI estimate.