Anting behavior in birds: the behavioral patterns and the interactions with ants in the subgenus Dendrolasius of the genus Lasius

Anting behavior, the application of ants or ant substitutes to plumage has been reported in more than 200 bird species worldwide. The peculiar behavior is highly stereotyped into two forms: active and passive. However, there is a paucity of detailed descriptions and explanations of this adaptative behavior in the past studies. This is mainly due to the low number of the observations in most of the species that practice anting. In the forests of central Japan, we observed the behavior of birds visited seven nests of ant species, Lasius spathepus and L. nipponensis, belonging to the subgenus Dendrolasius. As a result of observation from 2018 to 2020, a total of 305 visits by 20 bird species were recorded, and 102 cases of anting by eight bird species were confirmed. Of the 102 cases, 96 (94.1%) were carried out by three species: Turdus cardis, Garrulus glandarius, and Emberiza cioides. Anting by the three species was observed at the two study sites, which are approximately 90 km apart, suggesting that they constantly interact with the two ant species. Although any one anting session could not be clearly classified as either completely passive or active, each bird species exhibited behavioral patterns dependent on body size. New behavioral patterns were also confirmed: stamping and plunging. Additionally, in months when temperature and humidity were higher, anting occurred more frequently. This is the first case in which the characteristics of the anting are analyzed based on quantitative data. The observational data support the anti-parasite hypothesis as an adaptive explanation of anting: birds ridding themselves of ectoparasites and bacteria infection.