Black imported fire ants (Solenopsis richteri) have the remarkable ability to adapt its tool use: when provided with small containers of sugar water, they were able to float and feed on the surface, but when researchers reduced the surface tension, the ants started depositing sand grains on the inside of the container leading out of it. When faced with the risk of drowning, black imported fire ants (Solenopsis richteri) used sand to siphon liquid food out of containers. Image credit: Zhou et al. Tool use is seen as an indicator of cognitive sophistication and has mostly been observed in primates and some species of birds. But in invertebrates this behavior is less well studied and has previously been thought of as hard wired and inflexible. Black imported fire ants are native to South America but are now an invasive species in southern United States after being introduced. Their hydrophobic exoskeletons allow them to float on water but its likely that they still face frequent drowning risk in nature because of the importance of liquid foods like nectar and honeydew as a carbohydrate source. 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 senior author Dr. Jian Chen, an entomologist at the U.S. Department of Agricultures (USDA) Agricultural Research Service (ARS). In the study, Dr. Chen and his colleagues, Dr. Aiming Zhou of Huazhong Agricultural University and Dr. Yuzhe Du of USDA-ARS, calculated drowning risk by measuring the proportion of drowned ants in 2.5 cm containers of sugar water with differing concentrations of surfactant. The ants were able to float on the surface of pure sugar water, but the proportion of drowned ants increased significantly with increasing concentrations of surfactant. The researchers then provided ants with sands of varying grain size to test their preferences in creating sand structures when faced with different drowning risks. 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, Dr. Zhou said. 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. The sand structures were found to be so efficient that they could siphon almost half of the sugar water out of the containers in 5 min. Our findings suggest that ants and other social insects may have considerable high cognitive capabilities for unique foraging strategies, Dr. Chen said. The study was published in the journal Functional Ecology. _____ Aiming Zhou et al. Ants adjust their tool use strategy in response to foraging risk. Functional Ecology, published online October 7, 2020; doi: 10.1111/1365-2435.13671 ……