Thanatosis

Thanatosis is the term used to designate the defense behavior of some species. The anti-predatory strategy is to pretend to be dead to escape the predator’s attack. The species that practice this defense, when they perceive danger, temporarily stop their movements through the central nervous system, being totally paralyzed.

How and why does it happen?

But does it really work? The technique works, because normally the predators present in the nature take care when choosing their prey. Most of them prefer moving prey, discarding dead prey. The position of the prey, supposedly dead, may indicate unpalatability and make digestion impossible. As an example, we can mention spiders, which only feed on insects that are alive.

The theatrical technique of death simulation involves from wandering movements to the position with the back to the dog with the limbs shrunk, typical of a real post-mortem situation. The species that adhere to tannosis are thus paralyzed for many minutes. There are also cases of species that use this technique in the mating period to attract females – such as wolf spiders, for example -. Another reason is to pretend to be dead after mating when it comes to females who practice cannibalism, thus having more chances of escaping with life. The duration of tanatose can vary from 30 seconds, as in the case of the cane toad, up to 30 minutes, as in the case of the spider Hoplobunus mexicanus .

Practicing species

As an example, we can mention anuran amphibians, skunks, graceful cuíca, American opossum, beetles and arthropods of various orders, such as opil and some spiders. Among Brazilian species, we can present some examples such as the crab Trichodactylus panoplus , the lizard Liolaemus occipitalis and the frog Physalaemus kroyeri.

With that, we noticed that there are species that are adept of tannosis both among mammals and among amphibians, reptiles and arthropods. However, arthropods have the lowest number of occurrences.

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