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Biodiversity & Environment

The Andamans’ New Colonisers

  • 11 Aug 2018
  • 4 min read

The Indian bull frog, a recent arrival from the mainland, is steadily occupying the islands’ ecosystem and threatening the local economy. However this is not the only invasive species on the island.

  • The other invasive species are elephant(introduced for logging and later abandoned), chital, hog deer, and barking deer.
  • Giant African Snail, one of the 100 worst invasive species as described by the International Union for Conservation of Nature (IUCN), has now established itself as a major agricultural pest.
  • An invasive species, also called invasive exotics or exotics, is a species that is accidentally or artificially introduced into a biosphere where it is not normally found. In the absence of a natural predator, as it generally happens, the invasive species thrives and causes economic and environmental damage due to the imbalance created by its introduction.
  • The invasive species are more threatening on islands as the islands have few and unique species, which are irreplaceable. They are found no where else in the world. This makes the entire food web in the islands very different from that of the mainland. Unlike the mainland, resources on the islands are scarce for big animals, while natural calamities are more frequent.
  • Island species are evolved to cope with natural disaster, but they have little capacity to withstand rapid, human-induced impacts.
  • The Convention on Biological Diversity has said that invasives have contributed to 40% of all animal extinctions since the 17th century. The IUCN has formulated guidelines for managing invasives specifically in islands, largely involving data collection, community engagement, policy measures and management plans.
  • India is one of the very few countries in the world that does not have an invasive species policy.

Indian Bullfrog

  • Scientific Name: Hoplobatrachus tigerinus
  • Common Name: Bull Frog, Golden Frog, Tiger Frog etc.
  • IUCN Red List Category & Criteria: Least Concern
  • Native: Afghanistan, Bangladesh, India, Myanmar, Nepal, Pakistan
  • Indian Wildlife Act 1972: Schedule IV (Animals not in danger of becoming extinct; hunting invokes penalties)
  • Following the decline of natural fish stock after the 2004 Tsunami, the local administration encouraged integrated farming, with aquaculture in agricultural ponds. The fishling stocks (mostly from Kolkata) released into some of these ponds were contaminated with bullfrog eggs and tadpoles. This may have led to arrival of Bull Frog on the island.
  • It gulps down anything that would fit in its jaws: centipedes, leeches, native frogs, lizards, small snakes, and even chicks and ducklings, which are an important source of food for the islanders.
  • Adult bullfrogs pose a threat to small endemic vertebrates (from frogs to birds). Bullfrogs not only eat the native frogs, even their diets overlap, indicating a possibility of competition.
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