Forensic anthropologists rely on the state of decomposition of a body to estimate the PostMortem-Interval (PMI) which provides information about the natural events and environmental forces that could have affected the remains after death. Various factors are known to influence the rate of decomposition, among them temperature, rainfall and exposure of the body. However, conflicting reports appear in the literature on the effect of body size on the rate of decay. The aim of this project was to compare decomposition rates of large pigs (Sus scrofa; 60 -90 kg), with that of small pigs (< 35 kg), to assess the influence of body size on decomposition rates. For the decomposition rates of small pigs, 15 piglets were assessed three times per week over a period of three months during spring and early summer. Data collection was conducted until complete skeletonization occurred. Stages of decomposition were scored according to separate categories for each anatomical region, and the point values for each region were added to determine the total body score (TBS), which represents the overall stage of decomposition for each pig. For the large pigs, data of 15 pigs were used. Scatter plots illustrating the relationships between TBS and PMI as well as TBS and Accumulated degree days (ADD) were used to assess the pattern of decomposition and to compare decomposition rates between small and large pigs. Results indicated that rapid decomposition occurs during the early stages of decomposition for both samples. Large pigs showed a plateau phase in the course of advanced stages of decomposition, during which decomposition was minimal. A similar, but much shorter plateau was reached by small pigs of >20 kg at a PMI of 20-25 days, after which decomposition commenced swiftly.This was in contrast to the small pigs of <20kg, which showed no plateau phase and their decomposition rates were swift throughout the duration of the study. Overall, small pigs decomposed 2.82 times faster than large pigs, indicating that body size does have an effect on the rate of decomposition.

Concentrations of total Aluminium (Al) and Iron (Fe) were determined in Lake Oreochromis mossambicus was along a mean sequence of intestine > yellow body fat > brain > gills > liver > heart > white body fat, while the mean sequence of total Al and Fe in Micropterus salmoides was: intestine > gills > liver > heart > brain > white body fat. From the levels of Al detected in the yellow body fat of the studied fish species Oreochromis mossambicus, we suggest that this phenomenon may be related to the feeding habits of this species. Furthermore, the intake of certain species of phytobenthos by Oreochromis mossambicus could have played a role in the bioaccumulation of Al in the food chain and the possible development of pansteatitis in predators at higher trophic levels.

Abstract. Nile crocodile (Crocodilus niloticus) mass mortality events in the Olifants River between the Letaba River confluence in South Africa and Lake Massingir in Mozambique have been attributed to pansteatitis: a disease that affects fat depots of the animals. The disease is also found in sharptooth catfish (Clarias gariepinus) in the same area, and the cause of the disease is attributed to pollution. Although the Olifants River Valley is polluted, the impact of interventions such as dam construction on biodiversity receives little attention. We show that the onset of the pansteatitis epidemic in crocodiles and sharptooth catfish at the Olifants/Letaba confluence coincided with back-flooding of Lake Massingir that changed the Olifants River from a rock and sand substrate river to a clay substrate lake. Isotopic analysis shows that sharptooth catfish shifted from a predominantly vegetarian to a piscivorous diet that is highly correlated with pansteatitis prevalence, and crocodiles and tiger fish (Hydrocynus vittatus) show coincident trophic level increases. The evidence suggests that the ecosystem change altered the structure of the lotic foodweb and that an exotic or extralimital fish has invaded the confluence and is the vector of the pansteatitis epidemic. The invasive fish species is yet to be identified. The pansteatitis epidemic is an unintended ecological consequence of damming this river.

This study compares the aetiology of pansteatitis in Lake Loskop, relative to two other impoundments along the Olifants River. Macroscopic and microscopic pathology, age determination and analysis of stomach content, fatty acids and stable isotopes explain the high prevalence of pansteatitis in Oreochromis mossambicus (Peters) and several other species in Lake Loskop. All the dietary indicator comparisons between pansteatitis-affected and healthy fish fail to support a systemic cause. Pansteatitis in Lake Loskop was linked to size and weight of O. mossambicus, but not to ontogenic age. Fish in Lake Loskop showed abnormally high omega-3 to omega-6 fatty acid ratios normally only found in marine fish with no significant difference in degree of assimilation of these fatty acids between pansteatitis-affected and healthy fish. This explains the vulnerability to, but not the occurrence of, pansteatitis. As a cause for the pansteatitis, these results point towards sporadic vitamin E-depleting trigger events, known sporadic fish die-off occurrences that provide surviving fish with a rich source of rancid fats on which to scavenge. The mechanism ties pansteatitis to eutrophication and trophic cascade effects, the intrinsic drivers of the disease and suggests an adaptive management strategy that might be applied by relevant conservation authorities.