March 4, 2016
Thanks to student blogger, Lauren Smith, for this entertaining post about why Blue Jays engage in “anting.”
Imagine that you are an ant. Bright sunlight streams down, warming the white pavement stretched before you. You peer out from between cool green stalks and wave your antennae, sensing for any dangerous chemicals wafting your way. Tasting none, you scurry across the concrete, dipping and rising over the cracks as you go. Just as your anthill comes into sight, a shadow falls, thick and opaque, blotting out the sun. Suddenly, the pavement and the anthill fall away, and you are left with your legs waving in the air. Submerged over and over again into brilliant sapphire feathers, you deploy your only weapon of defense, a noxious formic acid that you spray behind you. The acid beads on the feathers, shining and iridescent in the sunlight, but it does nothing to stop the disorienting roller coaster you are locked in. With no other options, all that remains is to question: Why are you doing this to me?
This is precisely the question researchers Thomas Eisner and Daniel Aneshansley (2008) asked, when they observed this bizarre behavior in Blue Jays. “Anting” is the process in which a jay, with wings spread and tail tucked between its legs, grabs an ant in its bill and rubs it through its feathers before swallowing the ant. A couple of ideas have floated around over the years to explain why a bird might engage in this behavior, and the researchers set out to determine which of the two was most plausible.
The first idea was that Blue Jays were taking a bath in the ant’s formic acid, in the hope that it would rid them of the lice, mites and other parasites living in their feathers. Upon exposing those parasites to formic acid, however, scientists found that the acid has little to no effect on them. The second idea was that the Blue Jays had found a way to make the ants tastier by removing the acid before swallowing the ants. Formic acid is very bitter, so most birds don’t even attempt to eat ants. Getting rid of the acid could open up a whole new food resource! If the Blue Jays weren’t taking a bath, then perhaps they were preparing dinner?
To test this idea, Eisner and Aneshansley offered six different Blue Jays two types of ants: one with the acid glands removed and one with the acid glands intact. When the birds encountered ants without acid, all six gobbled them up, no “anting” necessary. When they encountered ants with acid, however, the “anting” routine resumed. The presence of formic acid, therefore, appeared to trigger the behavior! Excited, the ornithologists examined the contents of the ants before and after they were given to the Blue Jays, and found that the acid had been completely ejected onto the feathers. Even more interesting, they found that the Blue Jays grasped the ants so gently that they preserved the entire contents of the ants’ stomachs, retaining all the extra nutrients! The anting process allowed them to get rid of the disgusting flavor while maintaining the maximum amount of food in the ant. Once the formic acid is removed, they calculated that Blue Jays only need to consume 10 ants to have eaten the human equivalent of one scrambled egg; quite a nutritious meal indeed! So, the next time you have to make dinner, consider making Ants á la Blue Jay!
Eisner, T. and Aneshansley, D. 2008. “Anting” in Blue Jays: evidence in support of a food-preparatory function. Chemoecology 18: 197-203.
Lauren Smith is a senior at Cornell University studying neurobiology and behavior. She is minoring in creative writing, and is interested in the intersection between wildlife behavior, conservation, and education.