Elizabeth A. DiGangi

Scavenger Identification Strategies

When a scavenging species can be identified, knowledge of its taphonomic signatures and general foraging behavior can be applied to select appropriate recovery strategies and improve forensic interpretations of the remains and death scene. Evidence typically used in scavenger identification can be faunal (like scat, fur, or animal tracks), genetic, and/or from bite marks. However, faunal evidence often does not prove that a given animal interacted with the remains; genetic evidence is heavily dependent on the quality and quantity of available samples; and bite marks may be too distorted to be of much help. In addition to these approaches, components of an organism’s taphonomic signature (i.e., the patterns of soft tissue consumption, bone modification, disarticulation, and scattering) may be used to inform scavenger identifications. This chapter reviews the typical evidentiary forms for scavenger identification described above, and discusses how taphonomic signatures are shaped by an organism’s morphological characteristics, physiological requirements, and behavioral tendencies.

Unwitting Accomplices: Scavengers and Forensic Investigation

Vertebrate scavenging of human remains complicates the investigation of death scenes. Scavenger activity often interferes with death investigations by altering or destroying evidence, in both the remains and in the general context of a death scene. Postmortem damage produced by scavengers may hinder decedent identification, obscure or destroy trauma, scatter or remove remains and associated objects, and skew estimates of the postmortem interval or time since death. This chapter delineates the numerous ways in which scavenging by animals may derail traditional forensic methods, and thereby hinder evidence recovery, victim identification, and the forensic reconstruction of perimortem and postmortem events.

Suggestions for Future Directions

This concluding chapter addresses the persisting gaps on the taphonomic effects of certain taxa generally as well as for specific ecological contexts. There are several complex questions that would benefit from further research, including how to best address the effects that vertebrate scavenging can have on decedent identification, circumstances of death, and postmortem interval. In addition, an overview of topics that are missing from the literature or that would warrant additional investigation in forensic taphonomy is discussed, including known scavengers that are underrepresented in the literature. Finally, approaches that lend themselves to studying scavenging behavior within an ecological framework are provided, and a push for further development of standards for investigating scavenged death scenes is encouraged.

What Big Teeth You Have: Taphonomic Signatures of North American Scavengers

There are several taxa from vertebrate species of the North American scavenger guild that are important from a forensic standpoint. This chapter presents a summarized account of their habitats, distribution, behavior, morphology, and taphonomic signatures on bone and soft tissue. Case studies from the literature are used to illustrate or highlight particular behaviors or signatures. Distribution maps and photographs of several taxa are included, as are tables that summarize ecological and morphological characteristics of each species such as habitat, dental formula, animal size, conservation status, and typical taphonomic signatures. The taxa and species discussed include canids (i.e., the family that includes dogs), vultures, deer, corvids (i.e., the family that includes crows), crocodilians, opossums, felids (i.e., the family that includes cats), raccoons, rodents, sharks, pigs, and bears.

Ecological Influences on Scavenging Behavior

Scavenger behavior, and therefore the resultant taphonomic effects on human remains, is heavily influenced by interactions with the scavengers’ environment and other organisms within their biological community. This chapter overviews the effects of several ecological variables on scavenger behavior. Environmental and climatic variables influence the likelihood of remains being scavenged by any given species. The timing of the onset of scavenging after death by vertebrate scavengers and their competitors, namely microorganisms and necrophagous insects, is also affected by such variables. Changes in the composition of the biological community also influence the likelihood of carrion utilization by different members of the scavenging guild by affecting the availability of carrion or alternative food resources, or by affecting the frequency and outcomes of competitive interactions between scavenging species. Human presence can also impact the behavior of scavengers, often reflecting scavenger avoidance of human activity, although some species may tolerate or even benefit from an anthropogenic environment.

Adapting Your Investigation: Recovery and Interpretation

Forensic archaeology as well as key archaeological terms, such as context, association, and provenience are defined, and the benefits of using archaeological methods at outdoor death scenes is presented. Several specific examples from the literature are given regarding how adapting a particular search and recovery strategy with scavenger presence in mind is beneficial. The effects that scavenging can have on postmortem interval estimation are discussed, as is the effect scavengers can have on the ability of the anthropologist to distinguish between perimortem trauma and postmortem damage. This chapter concludes with best investigation practices for outdoor scenes that incorporate knowledge of local scavenger behavior and ecology, and provides a theoretical example of how the strategy may be applied in practice.

There Is No Such Thing as a Free Lunch: The Evolution of Scavenging

Abstract Scavenging is a foraging strategy in which carrion, or dead animal tissue, is consumed to meet energetic demands. Most animals are facultative scavengers, meaning that they scavenge when given the opportunity to supplement other methods of food acquisition, such as hunting or grazing. The evolution of scavenging behavior has been promoted by the high energetic quality of carrion resources. However, complete reliance on scavenging has been constrained by carrion’s unreliable availability and its rapid depletion given high levels of interkingdom competition. Today, only vultures are committed to exclusive carrion consumption. This chapter reviews the evolution of vertebrate scavenging and demonstrates how species maximize the nutritional benefits of a scavenging strategy through physical or behavioral adaptations that improve foraging efficiency, promote carrion monopolization, or otherwise preclude carrion utilization by other scavengers and decomposers.