The Odd Reason Why Ants Play Dead in Perfect Synchrony

Ants play dead in perfect synchrony, researchers discover. This is an unprecedented discovery that marks a before and after.

Isabel Cara

We have an unknown world of ants under our feet, hundreds of species of which much is still unknown. Death spirals have been observed among their most erratic behaviors, but now, in a world first, they have been shown to use death to their advantage by intentionally dropping themselves to save their lives.

A team of researchers from the University of South Australia was monitoring possum and bat nests on Kangaroo Island when they came across serendipity. When they opened one of the nest boxes they observed a complete colony of Polyrhachis femorata ants. At first, everything seemed to be clear; the entire colony had suffered a tragic death and were all lying on the floor of the nest, but suddenly there were small movements, and it turned out that they were not dead!

After a while, the whole colony began to move little by little. It was all a mimetic strategy to deceive their predators. This type of behavior has been observed in some other insects, but always individually. However, this time it was different, as there seems to be a kind of communication between the whole colony of Polyrhachis femorata ants; they acted as a well-synchronized entity even to play dead.

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Synchronous Thanatosis

Such behavior has never been observed before in other types of insect colonies. This is why the researchers were really excited because although there is a whole world of ants under our feet, little is known about them. Moreover, this is also the first recorded sighting of Polyrhachis femorata ants on Kangaroo Island in southern Australia.

“The mimicry was perfect. When we opened the box, we saw all these dead ants… and then one moved a little bit. This type of defensive immobility is known only among a few ant species, in individuals or specific molds, but we know of no other cases where it has been observed in entire colonies,” explains wildlife ecologist Topa Petit, who is also a co-author of the paper published in the Australian Journal of Zoology.

Although the behavior of the colony as it synchronously became dead is a world first, Petit explains that it is not that simple. “In some of the boxes containing colonies of Polyrhachis femorata, some individuals took a while to stop moving, and others did not stop. The triggers for the behavior are difficult to understand.”

The research team has said that it is possible that the behavior of falling over dead, called thanatosis, is also present in other ant colonies. So they hope their research will help other ethologists understand more about ants, insects that are little studied.

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An Endangered Species

The Kangaroo Island Nest Box Project aims to monitor 901 box cavities on 13 diverse properties as part of wildlife recovery efforts following the devastating wildfires of 2020. The program is charged with keeping safe possums and bats that suffered massive destruction of their natural habitats following the wildfires.

Now that the project has allowed researchers to learn not only about mammals but also about invertebrates, they have discovered that the species Polyrhachis femorata was probably also severely affected by the fires. But there is hope after the discovery: “Polyrhachis femorata is strongly associated with the critically endangered Narrow-Leaf Mallee community, where it colonized several boxes very quickly. However, we also have records from two other properties further west, indicating that the ants will use other habitats.”

Story written in Spanish by Alejandra Martínez in Ecoosfera