Comparison of data from a variety of environments and ambient temperatures has previously been difficult as few studies used standardized measures of time/temperature and decomposition. In this paper, data from previous studies and recent experiments are compared using simple conversions. These conversions allow comparison across multiple environments and experiments for the first time. Plotting decomposition score against logADD allows the exponential progression of decomposition to be expressed as a simple linear equation. Data comparison from many environments and temperatures shows no difference in decomposition progression when measured using Accumulated Degree Days. The major effector of change in rate was insect presence, regardless of depositional environment, species, or season. Body size is significant when carcasses are accessed by insects; when insects are excluded, while bodies are indoors, submerged, or buried, then decomposition progresses at the same rate regardless of body size.
Although the relationship between decomposition and postmortem interval has been well studied, almost no studies examined the potential effects of physical disturbance occurring as a result of data collection procedures. This study compares physically disturbed rabbit carcasses with a series of undisturbed carcasses to assess the presence and magnitude of any effects resulting from repetitive disturbance. Decomposition was scored using visual assessment of soft tissue changes, and numerical data such as weight loss and carcass temperature were recorded. The effects of disturbance over time on weight loss, carcass temperature, soil pH and decomposition were studied. In addition, this study aimed to validate some of the anecdotal evidence regarding decomposition. Results indicate disturbance significantly inversely affects both weight loss and carcass temperature. No differences were apparent between groups for soil pH change or overall decomposition stage. An insect-mediated mechanism for the disturbance effect is suggested, along with indications as to why this effect may be cancelled when scoring overall decomposition.
This article reports results of a comparative study of decomposition rates of wild rabbit (Oryctolagus cuniculus) which were either (i) buried after exposure to insect activity, (ii) buried without exposure, (iii) kept above ground behind an insect screen, or (iv) continuously exposed above ground in a field experiment. Results showed that dipteran oviposition occurred consistently in groups i and iv only. Decomposition rates (measured by Total Body Score every c. 50 accumulated degree days [ADD]) of rabbits kept behind the screen and those buried without exposure showed no difference (p = 0.450). This was significantly slower than those buried after exposure (p = 0.0016) which was in turn significantly slower than those continuously exposed (p << 0.001). Temperatures collected from animals showed the presence of feeding larvae increased intra-abdominal temperatures to >5°C above ambient. The findings support the assertion that insect presence is the primary agent affecting decomposition rate via tissue consumption and also the heat they generate.KEYWORDS: forensic science, taphonomy, insects, decomposition, degree-days, terrestrial, burial Although long utilized by entomologists and introduced to human decomposition research by Vass et al. in 1992 (1), forensic anthropologists have been slow to accept the standardization of time ⁄ temperature (accumulated degree days [ADD]) as the x-axis event timeline for decomposition; even some of the most current publications indicate that it has not been incorporated into research designs or data analysis (2-4) and reluctance to accept the implications of results generated by its use appears to be common. An analogy to an understanding of ADD is quite simple: for example, a pot of water on the stove at low heat may take 15 min to boil, whereas the same volume of water in the same pot will boil in 5 min if the heat is turned up. The same endpoint is reached, the pot boils-at the same accumulation of heat energy; the amount of chronological time it takes the pot to boil is incidental, as long as the right amount of heat energy accumulates.A slightly more complex analogy is to basic chemistry, where the input of thermal energy increases the speed of a chemical reaction. Hence in decomposition studies, ADD records the input of thermal energy (temperature multiplied by time) and measures the reaction (decay, measured in total body score [TBS]) to that input. Thus, the number of days it takes a corpse to skeletonize is incidental to the amount of thermal energy required to reach skeletonization. To continue the analogy, the experiment discussed in this article explores the use of a catalyst, to further increase the rate of decomposition in relation to ADD. In this experiment, the catalyst is insect access and, more specifically, the action of maggots.Recently published data (5) indicate that, when the accumulation of temperature over time is standardized by using ADD, insects influence the rate of decomposition more than any other variable. Simmons and colleagues (5) s...
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