Smarty Ants: Siphoning Sugar Water with Sand
- Poppy Simon
- Oct 21, 2020
- 2 min read
Black imported fire ants not only use sand as a tool to stop themselves drowning in liquid food, they also change how they use it according to the drowning risk.
Ecologists from China and the US have shown that black imported fire ants, Solenopsis richteri, can use sand to siphon sugar water out of a container by making and then joining up sand piles inside and outside the dish. The ants also changed what type of structure they built depending on the surface tension of the liquid, which affected the risk of them drowning.
The ants can float on a pure solution of 15% sugar water, but when a surfactant is added to the water, this decreases the surface tension and they can drown. The research team, led by Aiming Zhou, added different amounts of surfactant to a 15% sugar solution in a food container and presented the ants with sand to see what different kinds of structures they would make.
The ants varied the size of their sand piles inside and outside the container according to different surface tension of the liquid inside in order to both increase the effectiveness of the siphon and prevent drowning. When just a little bit of surfactant was added, the ants mostly deposited sand inside the container, but when surface tension decreased even more, they made bigger piles of sand outside the container to siphon the sugar water out without having to climb into the dish.
That the ants seem to be able to assess the risk of drowning and not only adapt their behaviour but change how they build their sand structures suggests a level of cognition and flexibility in tool use previously only seen in vertebrates. The authors suggest further work should be carried out looking at foraging strategy in social insects like ants and bees to try to boost our knowledge of invertebrate tool use. Seems like a great opportunity for some home experiments too... (perhaps without the drowning though!)
Zhou, A, Du, Y, Chen, J. Ants adjust their tool use strategy in response to foraging risk. Funct Ecol. 00: 1–12 (2020)
That is fascinating. How on earth have insects learnt to do this? Do they already do the equivalent of this in the wild I wonder?