Author ORCID Identifier
Year of Publication
Doctor of Philosophy (PhD)
Agriculture, Food and Environment
Dr. Xuguo Zhou
Death of individuals from the same species represents potential risks from disease, predation or competition for animals. Diverse responses associated with death have evolved ranging from simply avoiding or being attracted to the corpses in solitary animals to complicated undertaking behavioral repertoire in eusocial insects. A systematic review in chapter 1 suggested cannibalism is an ancestral and widespread death-related behavior in all non-human animals. Termites are suggested to switch their undertaking behavioral responses from cannibalism to burial based on interactions between chemicals associated with death to balance risks and benefits associated with decomposition. In eusocial animals like termites with caste differences, conspecific death from different castes or different causes might deliver different types of risks to living members. However, whether termites are capable of distinguishing differences in conspecific death and responding accordingly remains unknown. In chapters 2 and 3, the eastern subterranean termite, Reticulitermes flavipes, was found to manage corpses from different castes or causes differentially based on both qualitative and quantitative differences in their chemical profiles. R. flavipes workers cannot distinguish dead individuals caused by termiticides apart from those killed by naturally occurring abiotic factors. Death by biotic factors accelerated the release of late death cues and the deployment of burial behavior in nestmate workers. Corpses of all castes were carried inside the nest and cannibalized when the postmortem time wasbehaviors, such as walling-off and movement of the corpse before burial were observed for 50% of soldier corpses. Postmortem chemical profiles showed that the early death cues, 3-octanone and 3-octanol, in worker corpses were significantly higher than in soldier corpses, while they were undetectable in nymphal corpses. In addition, we confirmed the existence of 3-octanol and 3-octanone in the head, thorax, abdomen, and hemolymph. Higher concentrations of early death cues were detected in the head and thorax than in the abdomen, suggesting the possible location of synthesis. Ultra-low temperature did not affect the amount or concentration across body parts, suggesting the synthesis of early death cues occurs prior to death.
Our findings suggest termites equipped with delicate risk assessments on different types of conspecific death based on chemical signatures: cannibalism was the prior strategy dealing with freshly killed corpses to recycle nutrients and remove potential risks from pathogens or pesticides, whereas burial would happen when risks from disease or competition/intrusion overcome benefits associated with nutrition recycle. This study provides insights into the understanding of mechanisms of chemical-based “death recognition” in non-human animals, providing potential opportunities for further evolutionary studies of death-related behaviors.
Digital Object Identifier (DOI)
Shi, Jizhe, "MANAGING DEATH IN TERMITES" (2023). Theses and Dissertations--Entomology. 70.