NILGIRIS: A rare behavioural study by researchers in the Nilgiris has documented two crow species engaging in anting using the invasive yellow crazy ant (Anoplolepis gracilipes), marking the first recorded instance of the species being used for the self-maintenance behaviour in South India.
The study, Need Some Ants Too: Heterospecific and Conspecific Social Facilitation of Anting in Congeneric Crows from India, was carried out in January by researchers N Moinudheen, A Abinesh, G Gajal, K Rishi, E Vignesh, M Shahir, M Saran and A Samson. The team recorded the behaviour on video in Coonoor.
The researchers observed a large-billed crow (Corvus macrorhynchos) actively anting on a cypress tree inhabited by a large colony of yellow crazy ants. Three house crows (Corvus splendens) later approached the site, with two eventually displaying the same behaviour after watching the large-billed crow, pointing to heterospecific social facilitation, where one species adopts a behaviour by observing another.
Anting, though reported in more than 200 bird species worldwide, is seldom witnessed in the wild. During active anting, birds deliberately pick up ants and rub them onto their feathers, while in passive anting they position themselves over ant colonies, allowing ants to crawl through their plumage. The behaviour is believed to help control parasites, maintain feathers and harness the insects' defensive chemicals.
"We observed a large aggregation of yellow crazy ants (Anoplolepis gracilipes), one of the world's 100 worst invasive alien species. Both large-billed crows and house crows engaged in anting in association with the colony. This is the first documented record in India of Anoplolepis gracilipes being used for anting and a rare behavioural observation in these crow species," said researcher A Abinesh.
Researcher K Rishi said active anting accounted for nearly 42-45% of the large-billed crow's observed activity. The bird repeatedly rubbed ants on its tail, wings and legs, while collecting and pecking at ants made up another 8-10% of the observation period, suggesting it retrieved the ants after anting.
Explaining the social dimension of the behaviour, researcher N Moinudheen said heterospecific sociality enables animals to acquire information by observing members of other species.
"Three house crows arrived while the large-billed crow was anting. The first watched and collected ants but did not begin anting. Soon after, two more house crows arrived and started anting from a perch opposite the large-billed crow, suggesting they adopted the behaviour after observing it," he said.