KASARGOD: Last week, when ecologist P A Sinu was walking through the Manampurath Kava, a sacred grove in Nileshwar in Kasaragod, he saw a shocking, but not surprising, sight. A group of the all-invasive yellow crazy ants carrying a live and healthy caterpillar to their colony.
“That’s why these ants are such big a threat to the diversity of sacred groves,” said Dr Sinu, who is an assistant professor in the department of zoology at the Central University of Kerala. The yellow crazy ants have broken one too many rules of nature, said T P Rajesh, a PhD scholar. Together, they have been monitoring ants in 11 sacred groves in south India for the past six years.
“The share of yellow crazy ants among ants has increased from 5.4 per cent in 2013 to 34 per cent in 2019 in the rural sacred groves,” said Rajesh.In the process, these invasive species pushed out natives ants — who had specific functional roles to play — and were replaced by new sets of native ants comfortable with crazy ants. “This is like Scar bringing in the hyenas after killing Mufasa in ‘The Lion King’,” said Dr Sinu.
Rajesh said 35 native species of ants found in 2015 were missing in 2019 in the sacred groves. Instead, they found 26 new species in 2019. One of the casualties is the red weaver ant, promoted by farmers as biological pest control on coffee and cashewnut trees, said Dr Sinu.The findings of their study were published in Urban Ecosystems, an international scientific journal of Springer.
Yellow crazy ants, or Anoplolepis gracilipes, is a globally notorious invasive species. Natives of South East Asia, these ants were restricted to urban sacred groves up to 2015, said Dr Sinu.
Now, the tables have turned. To put this in perspective, the yellow crazy ants were the dominant ant species in urban sacred groves in 2013, but it was in the sixth position in rural sacred groves. But it increased its population to fifth in 2015 and became the numero uno in 2019, said Dr Sinu. “I would not have been troubled if not for its marauding nature,” he said.
At a high population size, the yellow crazy ants disrupt the bird’s nesting and attack and inflict lethal bodily damage to the few surviving chicks, he said quoting another scientific paper. But they are a bigger threat to the invertebrates such as caterpillars, butterflies, worms, and bees. While monitoring the crazy ants, Dr Sinu found that they entered the flowers of pumpkins, harvesting not just the nectar but also preying on the pollinators such as honeybees.
“They broke the nature’s rule. No other ant does that,” he said. Dr Sinu said the march of the crazy ants was an indicator that the sacred groves were disturbed and degrading.
“A pristine forest can resist invasive species,” he said. He said the government was investing in turning wastelands into small green islets. It should also focus on conserving the groves by fencing the groves, prevent disposing waste there, and incentivising the protectors of the groves, he said.