Portion size matters: carrion ecology lessons for medicolegal death investigations-A study in Cape Town, South Africa

Forensic taphonomic studies are regionally specific and improve time since death estimates for medico-legal casework. Within forensic taphonomy and carrion ecology, vertebrate scavengers are under-researched with many studies conducted using multiple, unclothed carcasses. This is a forensically unrealistic experimental design choice with unknown impact. The effect of variation in carrion biomass on the decomposition ecosystem, particularly where vertebrate scavengers are concerned, requires clarification. To assess the effect of carrion biomass load on vertebrate scavenging and decomposition rate, seasonal baseline data for single, clothed ~60 kg porcine carcasses were compared to clothed multiple-carcass deployments, in a forensically relevant habitat of Cape Town, South Africa. Decomposition was tracked via weight loss and bloat progression and scavenging activity via motion-activated cameras. The single carcasses decayed more quickly, particularly during the cooler, wetter winter, strongly correlated with concentrated Cape gray mongoose (Galerella pulverulenta) scavenging activity. On average and across seasons, the single carcasses lost 68% of their mass by day 32 (567 accumulated degree days [ADD]), compared to 80 days (1477 ADD) for multi-carcass deployments. The single carcasses experienced substantially more scavenging activity, with longer visits by single and multiple mongooses, totaling 53 h on average compared to 20 h for the multi-carcass deployments. These differences in scavenging activity and decay rate demonstrate the impact of carrion biomass load on decomposition for forensic taphonomy research. These findings need corroboration. However, forensic realism requires consideration in taphonomic study design. Longitudinally examining many single carcasses may produce more forensically accurate, locally appropriate, and usable results.