CHENNAI: When the ‘harmless’ spotted deer and ‘delicious’ Indian bullfrog was introduced from the country’s mainland into Andaman and Nicobar Islands, little was known about the threats they could pose to the fragile local ecosystem. The National Biodiversity Authority has now found that these deer are a ‘potential threat’ to the diversity of native plants and animal species in the islands.
Researchers have found that these deer cause changes, read reduction, in vegetation cover on the islands, which negatively influence abiotic factors such as temperature, moisture and light intensity. Besides, they also have unwanted impacts on beneficial soil-dwelling organisms such as microbes, insects and other smaller invertebrates and vertebrates. It results in a cascading of negative impacts in the natural food web.
The spotted deer was introduced in the island by the Britishers sometime around 1914, though the reason for the move is not known. Similarly, the bullfrog, which was introduced sometime after 2000, by people going from the mainlands, for consumption, also has had negative consequences. Experts say they are threatening the existence of native frog species. “These bullfrogs have managed to escape to the wild and expand their territory,” says Sandilyan, an expert on invasive species.
‘Govt must set up research cell’
The abundance of spotted deer has had far-reaching consequences on the ecosystem of the islands. Dr Sandilyan, a former fellow with the National Biodiversity Authority says researchers have found that degradation of the forest ground has had an impact on the native lizard population. It was found that the survival of subterranean egg-laying agamid lizards, such as coryphophylax species and skinks, was affected due to the changes in the vegetation cover.
Similar is the imapct of the bullfrog. Introduced for consumption, they are now threatening the local varieties. “These frogs continue to expand their territory as they are prolific breeders. They produce a clutch containing over 5,000 eggs within a short breeding season. Recent studies have shown that the tadpoles of bullfrogs have had an impact on the population of tadpoles of native species, because they eat them,” adds Sandiliyan.
Sandiliyan rues that a number of invasive species have been identified in the Andaman group of islands. However, there are no detailed long-term studies. The number of qualitative and quantitative studies done are poor. To control the entry of invasive species, authorities must strengthen regulations, says Sandiliyan.
“The government should take initiative such as setting up of regional invasive species research and management cell, to protect native species from becoming extinct.” Ironically, both spotted deer and the bullfrog are among the endangered species on the mainland, says Sandiliyan.