The animal kingdom is full of all kinds of predator-prey relationships, from head-popping hunting techniques to carefully evolved camouflage. Avoiding predators is a tricky job for many of the world’s animal species. Playing dead might be thought of as a fun trick to teach your pet but researchers in Australia have discovered that whole colonies of ants can feign death to avoid being eaten.
While checking pygmy possum and bat nest boxes on Kangaroo Island, Australia, researchers found an entire colony of southern broad-nosed spiny ants (Polyrhachis femorata) playing dead. The entire colony was so still, in fact, that the team believed that the group was in fact dead until one of the ants moved. They believe that this represents a world-first observation of this action by a colony of ants. This also marks the first time this species has been found on the island.
“The mimicry was perfect,” said Associate Professor S "Topa" Petit in a statement. “When we opened the box, we saw all these dead ants…and then one moved slightly. This sort of defensive immobility is known among only a few ant species – in individuals or specific casts – but we don’t know of other instances when it’s been observed for entire colonies."
Playing dead is seen in a range of species, typically mammals such as possums, who use this strategy to avoid predators. In insects, the technique is usually only seen in individuals, including other ant species, where their ability to keep still could mean the difference between being eaten.
Kangaroo Island was severely affected by bushfires in 2019-2020, and the team think the ant species were actively looking for new nest sites since they were found in areas of unburnt mallee habitat. The ants were also found to have plugged the entrances of the nest boxes with organic matter, possibly as further predator defence.
“In some of the boxes containing colonies of Polyrhachis femorata, some individuals took a while to stop moving, and others didn’t stop. The triggers for the behaviour are difficult to understand,” Petit continued.
The team suggest that while they can’t rule out the apparent behavior of the ants as submissive, defence, or to avoid detection by not moving, they believe the most likely explanation is that the ants were playing dead. They further suggest that smaller nests of ants may have greater success with this technique as a colony simply because there are fewer individuals to remain still at one time.
If a whole colony of ants playing dead doesn't impress you, check out what these snakes do to bamboozle their predators.
The paper is published in the Australian Journal of Zoology.