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1 September 2015 A test of the self-medication hypothesis for anting behavior in blue jays
Dakota K. Hutchinson, James S. Kellam
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Anting is a curious behavior that has been recorded in over 200 species of songbirds. While anting, a bird will wipe several ants throughout its plumage. It has been proposed that birds select ants for their ability to spray formic acid, a chemical that is known to have antibacterial properties at high enough concentrations that may help to limit the growth of feather bacteria. To test this hypothesis, two blue jays (Cyanocitta cristata) were provided with daily rations of either ants capable of ejecting formic acid (black carpenter ants, Camponotus pennsylvanicus) or ants incapable of ejecting formic acid (Western harvester ants, Pogonomyrmex occidentalis). After 26 daily sessions, it was found that a significantly higher percentage of black carpenter ants were used for anting when compared to the percentage of Western harvester ants. In the second part of the study, feathers inoculated with the common feather bacterium Bacillus licheniformis were treated with black carpenter ants to determine if the formic acid contained within these ants was at a high enough concentration to inhibit bacterial growth. A comparison between the mean number of B. licheniformis colonies on treated feathers with the mean number of B. licheniformis colonies on untreated feathers did not indicate that the formic acid sprayed by the ants had a significant impact on the growth of the bacteria. In conclusion, it appeared that formic acid is the trigger for the anting behavior but formic acid sprayed by ants does not have a significant antimicrobial effect against B. licheniformis. This suggests that there must be another function for the anting activity.

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Dakota K. Hutchinson and James S. Kellam "A test of the self-medication hypothesis for anting behavior in blue jays," BIOS 86(3), 144-151, (1 September 2015).
Received: 8 August 2014; Accepted: 1 March 2015; Published: 1 September 2015

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