Playing Dead – Why Do Animals Do It?

August 23, 2019
Playing dead (scientifically also known as thanatosis or apparent death) is an evolutionary strategy used by animals of different taxa as the last alternative to face a predator. It consists of faking death and has been underestimated until a few decades ago that it took a more relevant role.

Playing dead is a defense mechanism. The animal adopts this behavior, simulating death, as a protection technique against possible predators.

Origin of the term “thanatosis”

The word thanatosis is a combination of the Greek words thanat(o), which means “death“, and -ō-sis, which is equivalent to “process.” The combination of both gives us the expression “to carry out a death sentence.”

Therefore, zoologists subsequently redefined the word, which gives us the meaning that we have today. The community defined it as the “means with which some animals feign death in dangerous situations.”

This evolutionary strategy against predators also receives other names, such as “playing dead,” “apparent death,” or “tonic immobility.”

Everything about playing dead

A snake playing dead.

Predation is an important behavior in the life of wild animals, as it influences different aspects such as feeding and survival of both the offspring and the adults, among other things. The prey has developed different strategies to deal with their predators and one of them is playing dead.

In ecology, the interaction between a predator and its prey is studied. We can divide this interaction into stages and begins with the proximity of the individuals. It continues with detection, identification, approach, contact, submission and, finally, consumption.

Playing dead is also called “feigning death.” Many different species have adopted this anti-predator defense mechanism. Animals activate this technique when the predator is close to them or even after it’s established contact with them.

The most correct denomination is tonic immobility. Researchers believe it inhibits the additional attack of predators and the predator doesn’t apply the action of submitting more to the prey to prevent it from escaping.

The process of playing dead

The main characteristics that distinguish this strategy are the following:

  • Catalepsy or immobility. Rigid posture sustained by a pronounced tonic muscle activity.
  • Waxy flexibility of the limbs.
  • Lack of external stimuli.
  • They can stay in this state for seconds or hours.

Scientists consider playing dead to be a different strategy to immobility or freezing since the predator uses the latter before it makes contact. It’s also different from the mechanism of adopting a bristling posture. It seeks to intimidate the predator, as well as to protect vulnerable areas of the body. Instead, playing dead is the last resort.

The process of playing dead ends as quickly as it begins. The animal comes “back to life” in just a matter of seconds and reaches its maximum capacity despite having been in that state of absolute immobility. Until a few decades ago, there were few studies looking into this phenomenon. For that reason, this behavior is only registered in certain species, although many believe that it may be present in others.

Species that play dead

A dead possum on the road.

Different studies have determined the species in which researchers have observed this anti-predation mechanism. Many invertebrates such as spiders, butterflies, beetles, ants, bees, or wasps use it.

Vertebrates have also been seen to use it. Specifically, in five groups: mammals, reptiles, fish, birds, and amphibians.

However, the exact distribution of playing dead is not clear in vertebrates or invertebrates. Despite this, examples of this technique are shown below:

Ampedus nigricollis

This species of beetle has modified its morphology to adapt to the process of playing dead.

This beetle refolds the different parts of its legs. In addition, their antennae fold back, on the brow ridge and in the eyes.

Finally, the position adopted by this species gives rise to a cylindrical body, from which none of the parts protrude.

Pisaura mirabilis

A spider in its web.

The hunting spider has an unusual way of playing dead. Observations have shown that male spiders are more attractive to females if they bring them paralyzed prey. However, for the female spider, the male in motion may offer a more tasty snack than the paralyzed prey.

Therefore, males play dead when they have made the offering to the female. The males don’t stop playing dead until the females start eating the prey. Once the male “comes back to life”, the intercourse begins.

This behavior isn’t performed by all males. However, there are records of greater reproductive success in those males who partake in playing dead.

Other animals, such as ducks, cows, frogs, or reptiles such as the viperine snake (Natrix maura) or the western Iberian lizard (Psammodromus occidentalis), are on the list of species that play dead.

This defense mechanism is often ignored, despite having evidence at an ecological level and examples that apply in different species.

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