Researchers watch ants use tools to avoid drowning

Oct. 8 (UPI) — Scientists have observed ants using sand to draw liquid food out of containers. In addition to helping ants avoid drowning, the strategy allowed them to more efficiently collect sugar water.

Researchers described the first-of-its-kind observation in a new paper, published Thursday in the journal Functional Ecology.

When scientists first presented black imported fire ants with containers of sugar water, the ants were able to float and feed on the surface without drowning. When researchers added a surfactant, the reduced surface tensions forced the ants to adapt.

Faced with the threat of drowning, the ants collected and deposited sand grains inside the containers.

“We found the ants used sand to build a structure that could effectively draw sugar water out of the container to then to be collected,” lead study author Aiming Zhou said in a news release.

“This exceptional tool making skill not only reduced the drowning risk of ants, but also provided a larger space for them to collect sugar water,” said Zhou, an associate professor at Huazhong Agricultural University in China.

When foraging in unadulterated containers of sugar water, the ants declined to use sand or any other tools, but the addition of a surfactant changed the risk-reward calculus.

Scientists were able to trigger sophisticated tool use, as well as illuminate the ants’ ability to recognize shifts in foraging risk.

“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 co-author Jian Chen.

“Our findings suggest that ants and other social insects may have considerable high cognitive capabilities for unique foraging strategies,” said Chen, a research entomologist at the USDA’s Agricultural Research Service.

Black imported fire ants, Solenopsis richteri, are native to South America, but are now an invasive species in parts of the Southern United States. The ant’s hollow exoskeleton helps it float, but scientists suspect the insects still face a heightened risk of drowning as a result of their liquid diet. The ants rely heavily on nectar and honeydew.

Before allowing the ants an opportunity to demonstrate sophisticated tool usage, researchers had to figure out exactly how much surfactant would pose a problem to black imported fire ants. In the lab, scientists deposited the ants in containers of liquid with different levels of surface tension.

Once scientists knew how much surfactant to add to realize the risk of drowning, researchers presented the ants with a range of sand grain sizes. Researchers plan to repeat their experiments with different ant species in the future.

“Our experiments are conducted in the laboratory and only limited to the black imported fire ants,” said Chen. “Our study is the first to touch on this interesting topic. We hope our paper will motivate others to do the related investigations.”

Previously, sophisticated tool usage has only be observed among primates and some bird species. However, several previous studies have hinted at the ingenuity of ants.

One study proved ants are capable of collective cognition, while another showed ants can build bridges to cross gaps and form rafts to avoid drowning.

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