Protocol to classify the stages of carcass decomposition and estimate the time of death in small-size raptors

Abstract

One of the most common wildlife crimes involving birds worldwide is malicious poisoning. Post-mortem examination and toxicological analysis are essential for a proper diagnosis of the cause of the poisoning. However, investigators often require an estimate of the time of death, which is best determined by identifying the stage of carcass decomposition. The aim of this article is to propose a scoring method to classify the stages of carcass decomposition and thus provide an estimate of the time of death in small-size raptors. This protocol can be used by practitioners, forensic veterinarians, researchers, authorities and personnel collecting carcasses in order to standardize methods and minimize subjectivity. For this purpose, 12 carcasses of Common kestrel (Falco tinnunculus) were exposed to external weather conditions (in the period 4–19 July 2019) in Murcia, Southeastern Spain. The ambient temperature and relative humidity, body core temperatures and carcass weights were measured at intervals over the study period. Necropsies were performed (2 birds at each interval) at 1–2 h, 24 h, 72 h, 96 h, 7 days and 15 days after death. The necropsy of a previously frozen bird was performed to act as a comparison with non-frozen fresh individuals. Six stages of the post-mortem autolytic process were selected: fresh carcass, moderate decomposition, advanced decomposition, very advanced decomposition, initial skeletal reduction and complete skeletal reduction. To classify the carcasses according to these categories, a scoring method is proposed considering 5 parameters: state of the eyeballs, tongue/oral cavity, pectoral muscle, internal organs and other features. Several parameters affecting the process of the decomposition are discussed.