Giant African Snails Infest Chennai Why? – Free PDF Download


  • As the heavy rains lashed and flooded Chennai last week, the city saw an infestation of a unique kind. Over the last week, residents have spotted scores of snails on the walls, gardens, rooftops and waterlogged roads of the city.
  • This mollusk invasion continues to persist in several neighbourhoods, from Madhavaram in the north and Choolaimedu in central Chennai, all the way to the Pallikaranai marshlands in the south, the snails have been spotted everywhere.

Where did they come from

  • The snail in question is the Giant African Snail.
  • It made its way to Chennai hundreds of years ago, hitching a ride on trade ships during the colonial period. Native to countries of East Africa i.e Burundi, Ethiopia, Kenya, Tanzania, etc –

  • The Giant African Snail (scientific name: Achatina Fulica) was accidentally brought to cities in India through commercial activities.
  • But once they touched new soil, they quite literally conquered the land, eating all kinds of plants and crops.
  • These mollusks are even known on occasion to consume construction material including paint and stucco. Not only that, according to researchers the shells of these snails offer information on the rainfall rate of a particular region.

No natural predators

  • Today, more than seven decades after colonial rule ended, the Giant African Snail continues to thrive not just in Chennai and the rest of Tamil Nadu, but also in 12 out of 14 districts in Kerala, parts of Karnataka and the North East.
  • With no natural predators in the region, this highly invasive species has multiplied beyond measure in the region.
  • According to the International Union for Conservation of Nature (IUCN), the Giant African Snail is among the 100 most invasive species in the world.
  • The Giant African Snail and Hunter’s Slug end up in places with no predators and then explode in numbers, becoming an invasive species.
  • Plants and animal species native to a region co-evolve over millions of years. They grow and negotiate with each other and the plants learn to adapt and develop defenses against these creatures which prey on them.
  • But when taken to a new region, the ecosystem in that region has no defenses against this species.
  • The local vegetation and wildlife are taken by surprise, leaving the invasive species with zero threat and the freedom to populate without limit,” he adds.
  • While the Giant African Snail population has posed several challenges, most dangerously, it has turned into a formidable agricultural pest, feeding on over 500 different varieties of plants.
  • According to the New York Invasive Species Information, the Great African Snail resides in “plant habitats and preferentially consumes beans, peas, cucumbers and peanuts”. These snails can destroy whole farms.
  • In 2017, new research discovered a fascinating connection between the shells of the snails and the sub-seasonal rainfall received in the region where these mollusks lived.
  • Scrutiny of these snail shells, which grow faster during rains, can offer extremely fine-grained records of the rainfall received in the region.
  • The researchers were able to record week-to-week rainfall rates of past monsoon seasons by studying the shells of snails from as far back as 1918

Mating season

  • Like most snails, the Giant African Snails too are hermaphrodites – having both male and female reproductive parts. This means that 100% of the snail population have reproductive capabilities. And they reproduce a lot, helping them grow in population.
  • Each individual snail can lay up to 500-900 eggs, twice a year.

  • A recent study on the Giant African Snail (Achatina fulica) in Asia and Africa has found that the dangerous pest species had multiple episodes of invasion in India, particularly Kerala, and that new snail populations continue to arrive in India from snail-infested countries across the world.
  • The study observed that its population found in India had a higher genetic variety than those in the native African continent.
  • The higher genetic diversity found in our country indicates that the snail continues to have multiple invasions from different countries,” said Keerthy Vijayan, assistant professor, Kalasalingam Academy of Research and Education (KARE), Tamil Nadu.
  • The study done along with researchers from the Environmental Agency, UAE; Nottingham University; and Natural History Museum, London; found the same genetic strains of the snail population in India and the UAE.
  • The populations in India and the UAE share the same haplotypes (a set of genes within an organism inherited together from a single parent).
  • The snail could be introduced repeatedly back and forth in the UAE and India, considering material movement between the two countries,” said Dr. Keerthy.

Study period

  • Conducted at the Kerala Forest Research Institute (KFRI) with the support of the Kerala State Council for Science, Technology and Environment (KSCSTE) between 2016 and 2020, the study was published in the biological journal of the Linnean Society.
  • According to Dr. Keerthy, the snail reached Kerala for the first time when a researcher brought them from Annamalai University, Tamil Nadu, and accidentally released them at Elapully in Palakkad in the early 1950s.
  • Giant African snails are native to East Africa as the name suggests.
  • The height of the snails is around 7 cm and their length is approximately 20cm.
  • The shell of the snail is conical in shape and is double the height of its broad. The shell is also very tough.
  • The snails are said to eat plants, vegetables, fruits, paper, and cardboard. They sometimes also eat sand, very short stones, and bones from carcasses.
  • The snail is declared as one of the worst invasive species by the International Union for Conservation of Nature (IUCN).
  • The Giant African Snail is suspected to spread diseases like septicaemia, eosinophilic meningitis, and peritonitis in humans.

Q.Consider the following statements about Giant African Snails:

  1. Giant African Snails are gonochoric having both male and female reproductive parts
  2. The shell of the snail is conical in shape and is double the height of its broad. The shell is also very tough.

Which of the statements given above is/are correct?

(a) Both 1 and 2 are correct

(b) 1 Only

(c) 2  only

(d) Both 1 and 2 are incorrect




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