Date of Submission

5-5-2020

Document Type

Thesis

Advisor

R. Christopher O’Brien, Ph.D.

Keywords

Forensic Death Investigations, Stage of Decomposition, Pig Legs, Animal Scavenging

MeSH

Sus scrofa

LCSH

Human decomposition, Swine, Forensic taphonomy

Abstract

Forensic death investigations rely on postmortem interval estimations to establish a timeline surrounding a decedent’s death. Several methods are used, often together, to make such estimations. One of the main methods is the evaluation of the stage of decomposition; although decomposition follows the same general steps, the length of the process can vary by location and environmental factors. Animal scavenging can also impact decomposition by consuming flesh and impacting insect activity on the remains.

This study investigates the scavenging guilds and rate of decomposition of pig (Sus scrofa) legs on Rottnest Island, Australia. Three sites with unique environments were selected for the study: Bickley Point (marine), Forbes Hill (terrestrial), and Lake Baghdad (hypersaline).

The legs were placed on the ground at each location and secured with ropes, although experimental setup varied by site as needed. Photographs and video imagery were used to monitor the legs. The imagery was processed, and information regarding the experimental day, date, scavenging species, time of event, and event duration was recorded for each scavenging event. The stage of decomposition was assessed daily. Temperature, light intensity, humidity, and depth data were collected by data loggers.

The scavenging guilds observed at each site varied greatly, as expected. The primary marine scavengers were the Australian herring (Arripis georgianus), Banded Sweep (Scorpis georgiana), Brownspotted Wrasse (Notolabrus parilus), and Weeping Toadfish (Torquigener pleurogramma). The King’s skink (Egernia kingii) was the primary terrestrial scavenger. No scavenging on the hypersaline legs was observed.

The rate of decomposition also varied by site. All marine legs were in the water for only one day, so decomposition stages could not be assessed. The terrestrial legs remained fresh for two days post-deployment before the active decay began, and the legs became desiccated. The hypersaline leg remained fresh for two days before the bloat stage began and persisted for the remainder of the experiment.

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