Taphonomic Analysis of Rodentia and Lagomorpha Bone Gnawing Based Upon Incisor Size

Uncovering Forensic Taphonomic Agents: Animal Scavenging in the European Context

Simple Summary

In forensic cases of exposed human bodies, vertebrate animals frequently pose challenges concerning remains recovery, identification, and the interpretation of circumstances of death. For instance, they can remove body parts, destroy skeletal features, and create “pseudo-lesions” that complicate trauma analysis. With this review, we highlight vertebrate scavengers in Europe that are of forensic relevance, including their typical behaviour and their inflicted lesions on bones and soft tissues. Here, we support forensic practitioners in recognising animal activity at the site of discovery and in interpreting the circumstances of death. Our review serves as a guide for the examination of animal-altered human remains and their found state by providing ecological backgrounds on various vertebrate species. In addition, this study provides an overview of the current state of research in the field of animal scavenging in forensics.

Abstract

Animal scavenging by vertebrates can significantly alter human bodies and their deposition site. For instance, vertebrate animals can cause postmortem modification to a body, alter perimortem trauma, influence decomposition rates, disarticulate and scatter body parts or evidence, and affect the identification of the deceased. Animal scavenging is a relatively common occurrence in forensic investigations. Even so, studies on the subject are scattered and rare, with most focussing on geographical areas outside of Europe. For that reason, we intend to collate the literature to provide an account of forensically relevant vertebrate scavengers in Europe, their impacts on human remains, and their implications for forensic investigations. Here, we provide an overview of forensic aspects where the knowledge of animal scavenging is crucial, as well as an account of potential scavengers of human remains in Europe and their typical alterations to soft tissue and, in particular, to bones. In addition, we are the first to provide a guide for forensic practitioners to identify the presence of vertebrate scavenging and subsequently inform outdoor search strategies for affected human remains.

Multi-agent scavenging patterns in Hawai'i: A forensic archaeological and skeletal case study

Knowledge of the behavior of local fauna can aid forensic investigators in developing awareness of site formation processes. In Hawai'i, little has been published on the effects of feral domestic pig (Sus scrofa) and feral domestic dog (Canis familiaris) scavenging and bone dispersal on field recovery and laboratory observations. In this Pacific tropical setting, the most consequential terrestrial taphonomic agents are pigs and dogs, both in terms of hard tissue modification and dispersal of remains across the landscape. In 2017, an archaeologist discovered the remains of an unidentified decedent on the island of Kaua'i, State of Hawai'i during a cultural resource management survey. Subsequently, a forensic recovery team in conjunction with Kaua'i police and crime scene investigators used archaeological techniques, including pedestrian survey, tape-and-compass, and GPS mapping, to map and recover the remains. A feral pig trail transected various areas of the recovery site and corresponded with the distribution pattern of recovered skeletal material, including both the main concentration more broadly dispersed skeletal elements. While much of the skeleton was present, missing or unrecovered skeletal elements are consistent with expectations based on existing literature. Much of the postmortem bone deformations were characteristic of marks related to feral dog and/or feral pig scavenging. These results assisted local investigators in deciding the manner of death, as well as providing the family with an accounting of the decedent's remains for burial. Thus, forensic anthropologists and archaeologists need to understand and develop knowledge of local animal behavior to recover and interpret human remains of medicolegal significance.

Bone dispersal by vertebrate taxa in an urban park environment in New England, USA

The questions of the frequency, distance, and maximum size of the bones that carnivores, rodents, and other common taxa can disperse have been little addressed, especially in the later phases of skeletonization when individual bones are more subject to transport and loss. The present research utilized a sample of dry white-tailed deer (Odocoileus virginianus) bones in two locations in a forested urban environment dense with eastern gray squirrels (Sciurus carolinensis), chipmunks (Tamias striatus), coyotes (Canis latrans), raccoons (Procyon lotor), and other potential scavenging taxa. Game cameras were used to document their dispersal behavior. A total of 1731 visits were recorded, by a minimum of 12 mammalian and 9 avian taxa. Small amounts of dispersal impacted the bone samples continuously throughout the observation period, with 52.2% of all movement in the range of 1-5 cm. The bones were dispersed a maximum distance of 1252 cm, and the largest bone moved had an initial mass of 194.6 g. Rodent dry-bone gnawing behavior affected 72.7% of the sample. The project also assessed a smaller sample of Tile Mate® tracking chips for their utility in dispersal research, and these were found to have a useful potential though were not pivotal in acquiring the data presented here. Forensic surface search methods and interpretations of skeletal recovery patterns should take into consideration the ability of these common species to disperse even dry bones away from their initial locations, and this behavior may continue years after the time of initial deposition.

Forensic taphonomy: Vertebrate scavenging in the temperate southwestern Cape, South Africa

Vertebrate scavenging can significantly accelerate the rate of decomposition, which can hinder estimating the post-mortem interval (PMI). Patterns of decomposition and scavenging are highly specific to different environments in a forensic context, with no known data for South Africa. A better understanding of local decomposition patterns, taking scavenging into account, could increase the accuracy of PMI estimation and improve identification of human remains. Using a porcine model in the forensically significant thicketed Cape Flats Dune Strandveld habitat, the effect of vertebrate scavenging on the decomposition process was examined. This part of Cape Town suffers from poor socioeconomic conditions and a high murder rate, which is due in part to the dense population. Human decomposition was simulated using three small (∼20kg) domestic pig (Sus scrofa domesticus) carcasses, with ethical clearance. One pig served as a control and was caged to prevent vertebrate but not invertebrate access; the other two served as experimental treatments. They were deployed in Delft, Cape Town, and observed by motion-activated, time-lapse remote photography to record scavenger species and activity. A rapid increase in the decomposition rate was observed due to Cape grey mongoose (Galerella pulverulenta) scavenging, with early skeletonisation reached by both experimental pigs by day 14, compared to the control remaining in advanced decomposition after 93 days. Mongoose is the primary scavenger in this habitat, and showed notable patterns of feeding behaviour, exclusively within daylight hours. Scavenging activity was only influenced by rainfall later in the cycle. This research provides knowledge on locally relevant decomposition patterns and highlights the necessity for PMI estimation methods to consider vertebrate scavengers. This may improve human skeletal identification in forensic cases. There is scope for expansion of this study, with an investigation of seasonal effects, the interaction between invertebrate and vertebrate activity, as well as, the effect of clothing on scavenger access.

Forensic taphonomy: Scavenger-induced scattering patterns in the temperate southwestern Cape, South Africa - A first look

The effect of vertebrate scavenging can drastically alter the rate of decomposition and cause skeletal scatter, which hinders human forensic recovery and identification. Patterns of scavenging, disarticulation and scatter in a forensic context are specific to different environments with no known data for South Africa. A better understanding of these patterns can increase the chances of full body recovery and improve identification of human remains. In this preliminary study, the effect of wild vertebrate scavenging on skeletal scatter was examined using a porcine model in the forensically significant thicketed Cape Flats Dune Strandveld habitat. This area is a densely populated part of Cape Town, which suffers from poor socioeconomic conditions and a high murder rate. Ethics was granted for the use of three small (∼20kg) domestic pig (Sus scrofa domesticus) carcasses as proxies for human decomposition. They were deployed in Delft, Cape Town, and observed by motion-activated cameras to record wild scavenger activity. One pig served as a control and was caged to prevent vertebrate but not invertebrate access; the other two served as experimental treatments. Scatter was recorded every second day by marking the location of skeletal elements and measuring the distance and angle from the centre of each deposition site. No scattering was observed in the control, but notable scattering patterns were observed in the experimental pigs due to Cape grey mongoose (Galerella pulverulenta) scavenging, the only vertebrate scavenger species observed. No clear pattern of scatter distance over time was followed. Scatter began in the skeletonisation phase (day 25-30), resulting in a maximum distance of 12.67m and scatter/search area of 504.32m². Mongoose-induced skeletal scatter followed a distinct pattern of movement into dense undergrowth, a previously unobserved behaviour and a key finding of this study. These results provide baseline data for sub-adult human scatter, or scatter of smaller components of an adult human skeleton, as demonstrated in the forensic case example provided. Knowledge is provided on locally relevant decomposition patterns and informs search methods for improved human skeletal recovery in forensic cases. There is scope for expansion of this study, with an investigation of seasonal effects, the interaction between invertebrate and vertebrate activity, as well as, the effect of clothing on scavenger access.