Why do ants react to permanent marker lines? (Tracey)


My students and I explored how an ant would react to various ink lines (ball point pen and permanent marker). What we observed was the ant's behavior was not effected by the ball point pen lines, but it would veer away from the permanent marker lines at first....then cross the permanent marker line after a second or two. Can you shed any light on why the ant seemed repelled by the permanent marker line at first, and then why it seemed unaware of the same line later? (Tracey)


Hi Tracey!

Thank you very much for contacting us at AntAsk! It sounds like you are designing really cool and interesting projects with your students!

Two explanations for the behavior you and your students have observed are possible: (i) Ants could perceive the smell or (ii) the color of the markers. If ants perceived the smell, it could then fade after a few minutes (like when you paint a room and after a few days the smell has faded) or the ants could just get used to it. The other explanation could be that the ants react to the color, but then get used to seeing the line. But since you tested a ball point pen line as well and the ants did not react to that, I would guess that the smell is what deters them. To test that you could try several different types of pens (with different smells, in an ideal case you would have a pen that does not emit any smells) and to exclude the effect of color you could use a clear pen or a pen that has exactly the same color as the surface. If the ants react to a pen that is not visible, then it is more likely that the smell affects them. However, different ant species could perceive colors in different ways than humans. In a previous post we answered several questions on ants' senses and this post might provide interesting information for you when designing your experiments.

All the best,
Steffi Kautz & the AntAsk Team

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