A novel kind of tool use has been observed in black imported fire ants as a new study published in the journal Functional Ecology describes how they were seen using sand to draw liquid food out of containers. The never-before-seen approach appears to negate the insects’ risk of drowning by using the sand to draw sugar water out of a small well when the water surface tension wasn’t sufficient to keep them afloat.
The use of tools is considered a marker of cognitive sophistication and is widespread among primates and certain bird species. Invertebrates such as black imported fire ants (Solenopsis richteri) aren’t high on the list of suspected candidates for sophisticated tool use and yet a lab experiment revealed that they have been utilizing their environment in a way never before reported in science.
Black imported fire ants have hydrophobic exoskeletons that allow them to float on water, and when faced with a small container of sugar water, the ants were able to feed as they floated on the water’s surface. The researchers then altered the surface tension of the water by adding a surfactant, which put the ants at risk of drowning if they entered the water.
Amazingly, the ants were able to recognize the change in conditions and adjusted their approach accordingly. They began building structures using sand to siphon the sugar water out of the container and bring the delicious nectar to them. They were so sufficient in fact that they could drain the containers of almost half the sugar water in just five minutes. The ants never made the structures when foraging in containers of pure sugar water without the surfactant, indicating they can adapt their approach as and when they recognize changes in their environment.
"We knew some ant species are able to use tools, particularly in collecting liquid food; however, we were surprised by such remarkable tool use displayed by black imported fire ants," said study author Dr Jian Chen in a statement. "Our findings suggest that ants and other social insects may have considerable high cognitive capabilities for unique foraging strategies."
The study authors also express limitations to the study, having only investigated one insect species in laboratory conditions, but the discovery is the first of its kind to paint ants as a species of interest for novel tool-use behaviors.