Quantifying forensically relevant vertebrate scavenging: a pilot study to develop a methodological framework using Cape grey mongoose (Galerella pulverulenta) as an illustrative model.

Abstract

Currently, forensic death investigations in the Western Cape, South Africa do not account for vertebrate scavenging activity; however, previous research in the city of Cape Town has shown a significant impact on the rate of decomposition due to scavenging by the local Cape grey mongoose (Galerella pulverulenta). This pilot study aimed to develop a framework to more robustly quantifiably describe and analyse the scavenging behaviour of this species on a single clothed 60 kg porcine carcass in a forensically significant location in Cape Town (i.e., a region of the city with a proportionately large forensic case load). Feeding behaviours are the focus of this framework and analysis, but non-feeding behaviours in the immediate vicinity of the carcass are also distinguished and described. Additionally, it was assessed whether all behaviours varied in their frequency of occurrence as decomposition progressed. More than 40 h of mongoose interaction with the carcass were recorded using motion-activated infrared-capable wildlife trail camera videography. The highest frequencies of scavenging activity were observed in the abdominal and the eye socket regions of the carcass. Abdominal feeding largely involved soft tissue modification, whereas more intensive activity in the eye socket suggested a higher likelihood of hard tissue scavenger artefacts being found there. A Kruskal-Wallis test confirmed that some feeding behaviours occur more frequently during specific decomposition stages. For example, scratching is common during the earlier stages of decomposition, ostensibly to create an opening in the flesh. Twisting whilst biting was only observed in latter stages of decomposition, likely due to the increased toughness of the soft tissue as it desiccated. This pilot research offers detailed insight into scavenger behaviours previously unreported in the forensic taphonomic literature, and proposes a provisional method of quantifiable analyses of scavenger behaviours that extends what has previously been published in the forensic taphonomic literature. Local validation of the observations is planned, and international replication of the research for diverse scavenger guilds is encouraged.

Key points: Novel framework for detailed quantitative analysis of vertebrate scavenger behavior using the Cape grey mongoose as a model.First systematic study of scavenger behaviour in South Africa and likely Africa-wide.Cape grey mongoose preying on blow fly larvae, emphasizing the necessity of videographic documentation.