Evolution of death-related behaviors in non-human animals: a systematic review

A variety of strategies are used by animals to detect and respond to the corpses of their conspecifics. However, how these responses evolve and what factors influence the evolution of death-related behaviors remain unknown. Here, a quantitative review-based analysis of the evolutionary history of death-related behaviors among all non-human animals was carried out to further understand their evolution and their relationship to sociality. Our bibliometric study revealed a consistent rise in interest as well as a promising integration throughout the currently dispersed field of death-related research. Cannibalism was suggested as an ancient and common response to death in the reconstruction of ancestral states of death-related behaviors. Through a correspondence analysis, we also tested the “social complexity hypothesis” in death-related behaviors and suggest that the evolution of sociality precedes the expansion of death-related behavioral repertoires in terms of both scale and diversity but might not always be supported in some eusocial invertebrates. Evolution of death-related behaviors might be influenced by the specific evolutionary history of sociality within taxa and also factors other than sociality. By addressing the study's biases and limitations, we highlight the necessity of documentation of death-related behaviors in broader taxa, especially in eusocial vertebrate animals, and encourage further investigation of factors associated with such behaviors in order to enhance the reconstruction of evolutionary histories and provide a better understanding of the factors influencing the evolution of such behaviors.