Gavin Pitts

Thesis

Establishing a baseline of Crustaceans involved in cadaver scavenging in the West Australian marine environment

Summary

A baseline of sarcophagous crustaceans attracted to carrion in the ocean around Lancelin, West Australia was obtained by immersing the bisected carcass of two adult feral pigs (Sus scrofa) analogous in size to an human adult (between 60-80 kilograms) in four marine locations at Lancelin assessed as “typical” of the region’s marine environs. Each pig was placed in a 5 foot by 3 foot shark resistant steel cage, and the cages then sunk to the seabed at a depth of 15 metres (50 feet) Over a week, the cages were monitored for scavenging activity and samples of those scavengers taken.

On the first day of sampling, scavenging was undertaken primarily by reef fish and decapod crustaceans- in particular Malacostraca. On the fourth day after sinking the carrion, another sample was taken- fish were still present, though in greatly reduced numbers- the primary scavengers present were very large numbers of Amphipoda (several hundred) and numerous Malacostraca, which devoured not only the porcine carrion but also any reef fish that had entered the cage. The sixth day after sinking saw another sampling take place. Noted was a marked reduction of all scavengers, with amphipods still dominating but in far smaller numbers.

Why my research is important

To provide an initial baseline of marine scavengers that are drawn to cadaverous tissue as a food source in the marine waters of the West Australian region. At the time of writing, such a study has not yet been undertaken, and therefore such a baseline would be of great forensic value to future medical examiners presented with remains recovered from the ocean. Additionally, this study hopes to establish the existence of a succession wave of scavengers, including crustacean scavengers, drawn to a carcass in a predictable, repeatable manner during the various stages of cadaver decomposition; future studies might be able to expand upon this initial baseline research and establish succession patterns amongst marine scavengers and use crustaceans in situ in a manner analogous to those currently found amongst sarcophagous insects in a terrestrial death scene, and thus potentially use the predicted waves of marine scavenging fauna and knowledge of their life cycles to establish an estimated post mortem interval for human remains recovered in a marine context.