Killing Method Influences Decomposition, Entomofauna and Successional Pattern of Exposed Juvenile Pig Carcasses in Wukari, Nigeria

Abstract

Homicide-related crimes (especially juveniles) are serious problems in Africa and particularly, in Nigeria, with little success in apprehension of culprits recorded due to a lack of substantial forensic data to aid investigation processes. To aid the mitigation of this challenge, two juvenile pigs were killed (one by slaughtering and the other by strangulation) at the Research Garden of the Biological Sciences Department, Federal University Wukari, Nigeria. Both carcasses were left exposed to sunlight 25 m apart, while being protected from vertebrate scavengers using meshed metal cages. Observable postmortem changes on both carcasses were recorded while adult insect sampling using a combination of aerial net, pitfall traps and manual searching continued from the fresh to dry stages of decomposition for both carcasses. Data from sampled insects obtained were used to compute abundance, frequency of occurrence and dominance at each decomposition stage. Appropriate diversity indices were obtained using the Paleontological Statistical Tool-Past3, while similarity in entomofauna between both carcasses was determined using Jaccard’s index. Although both carcasses completed decomposition in 14 days, the strangulated carcass had faster active and advanced stages with prolonged dry stage vis-à-vis the slaughtered carcass. Also, the slaughtered carcass had higher insect abundance (895) than the strangulated carcass (781), with peak diversity and richness at the advanced stages. The slaughtered carcass was also observed to have higher diversity and richness values (1.942, 2.517) than the strangulated carcass (1.801, 1.597). Five (5) dominant insects (Hister monitor, Dermestes maculatus, Zophosis sp., Chrysomya chloropyga, and Pheidole sp.) invaded the strangulated carcass while Crematogaster sp. invaded the slaughtered carcass in addition to these. Overall, over 60% total species similarity and 80% dominant species similarity existed between the carcasses. Hence the killing methods used in this study largely influenced variations in the duration of the five decomposition stages, observable postmortem changes as well as insect abundance but the succession of invading insects was largely similar.