16 October 2017
Andrew Masterson
Andrew Masterson is a former editor of Cosmos.
Sisters are chewing it for themselves. In situations where a colony is formed by a pair of ant queens and one of them dies, the surviving matriarch will dismember the corpse and bury it.
Research from a team led by Christopher Pull from the Institute of Science and Technology in Austria observed the behaviour of co-founding queens of the black garden ant (Lasius niger) – a species wherein queens co-found colonies, usually in pairs, in about 18% of cases.
Co-founding is thought to be a response to limited suitable nest sites. The first days of a new nest is a draining and energy-intensive period for a queen. Until the first workers hatch, she is forced to subsist on nutrients released by the breakdown of their own fat and muscle.
Should one of a pair of co-founding queens fall ill – generally from a fungal infection – and die, the surviving queen faces a brutal survival choice.
Leaving the royal corpse where it lies means the survivor does not need to expend extra resources from its dwindling internal reserves. This strategy, however, increases the likelihood that the pathogen will spread, potentially also killing the survivor.
Disposing of the corpse, by means of biting it to dismember it, and then burying the parts, reduces the risk of transmission, but represents a severe and potentially fatal drain on the remaining queen’s nutrient reserves.
In a study published in the journal BMC Evolutionary Biology, Pull and his colleagues report that in experiments, where the pair of queens shared a chamber, 75% of the survivors would dismantle the corpse and 67% would bury it.
This strategy, the scientists found, reduced the risk of the surviving queen falling ill seven-fold. The results indicate that the traditional view of queens engaging in only a single behaviour – egg-laying – is wrong.
“This study expands our view about the challenges facing colony-founding ant queens, and how those challenges shape the evolution of queen behaviour, which appears to be far more complex than previously thought,” says Pull.
“The simplistic view of the founding queen, waiting patiently for her workers to emerge so she can assume the role of egg-producer, is clearly not a comprehensive picture.”