Perception of death in animals: Thanatology in nature
Death plays an essential significance in human life. Not only on a personal level but as a society, Homo sapiens have a conscious understanding of it. But have you thought about how other animals react to it?
To know death, you must know living. Animals have different cues to examine the phenomenon. Some animals avoid dead carcasses or corpses to prevent pathogen infections. Some animals are attracted to the dead, as they act as food for them. Let's see what cues animals depend on.
In insects, dead members of the hive or community are identified by scent-based hypothesis. Insects pick up on pheromones of the members through olfactory receptors. The absence of these chemical vital signs can cue towards the end of life. Fatty acids like oleic acid work as the biggest cue in invertebrates as death messengers. The dead bodies of insects are removed from the colony to avoid pathogen spread. It has also been observed that fruit flies age more rapidly when they are in the vicinity of other dead fruit flies.
In certain vertebrates, chemicals like cadaverine and putrescine act as molecules of death. These chemicals are major components of rotting carcasses and produce a foul odour. Many animals avoid dead bodies but certain animals like rats are attracted to such chemicals because of their feeding habits.
Many vertebrates like birds do alarm calls and show disdain when humans interact with corpses. Such cases were reported by scientists and are called mobbing.
In non-human primates, since the brain capacity has been increased they show more physical interactions with the dead body. Grooming, poking and even cannibalistic activity have been reported. Infant death among non-human primates has been addressed scientifically. In a controlled environment, a female dealing with infant loss showed no response to male calls in experiments.
Elephants are animals that show immense value and a deeper understanding of death. Asian and African elephants have been documented to show physical interactions such as touching the dead with trunks. Elephants live in herds with a matriarch in charge. Elephants, unlike other animals, guard the dead body from predators and contact the corpse for inspection. They inspect the corpse via their trunks by checking the nasal organs. Elephants cover their dead with branches, leaves, and soil essentially burying the dead. It has also been observed that elephants bury other small dead animals. Not only that, it has been observed that elephants can also revisit their dead. Elephants collectively vocalise to honour their dead. Cases of elephants inspecting the dead via skulls and tusks of the buried body have also been reported.
This complicated behaviour of elephants regarding death and their dead ones show that it's not only humans who understand the depth of it.
Death is a part of nature that follows all that breathes. All animals have different ways to differentiate living and dead and have different reactions and rituals to death. Implementation of thanatology (study of death and grief) in nature and biology is integral for understanding animal behaviours.
References:
Gonçalves, A. and Biro, D. (2018). Comparative thanatology, an integrative approach: exploring sensory/cognitive aspects of death recognition in vertebrates and invertebrates. Philosophical Transactions of the Royal Society B: Biological Sciences, 373(1754), p.20170263. doi:https://doi.org/10.1098/rstb.2017.0263.
Wisman, A. and Shrira, I. (2015). The smell of death: evidence that putrescine elicits threat management mechanisms. Frontiers in Psychology, 6. doi:https://doi.org/10.3389/fpsyg.2015.01274.