The Indian Express (Delhi Edition)
Overrun by invasive chital, a tiny Andaman island counts the cost
INTRODUCED TO the Andaman and Nicobar Islands for game hunting in the early 1900s by the British, a herbivore that multiplied unchecked for years in the absence of large predators has become an expensive and an “invasive” problem for the Union Territory’s authorities.
For years, the chital (spotted deer) — the staple food for large predators in forests of mainland India — sustained themselves on local ground vegetation on Netaji Subhash Chandra Bose Island, which lies east of Port Blair and does not have any major residential enclaves. But now, with the nearly 500 chital having depleted much of the low-ground vegetation, the Andaman and Nicobar Forest Department has been spending `15-20 lakh per month since the past few months to feed them on the island, a source told The Indian Express.
“There is negligible ground vegetation left on bose island( formerly Ross Island) because the chital population has stretched beyond the carrying capacity of the place,” said the source.
To deal with the “invasive species”, the department has been seeking solutions — to either rehabilitate the chital or relocate them elsewhere. Under the Wildlife Protection Act, 1972, an officer of the rank of Chief Wildlife Warden can permit translocation for the purpose of scientific management. The law mandates that such translocation should cause minimum trauma to animals.
On February 13, the Andaman and Nicobar Forest Department reached out to the Dehradun-based Wildlife Institute of India (WII), seeking its help in devising safe strategies to manage the deer population. The forest department told WII that it “intends to rehabilitate/relocate around 500 nos. of spotted deer presently located at Netaji Subhash Chandra Bose Dweep to Biological Park, Chidiyatapu (a mini zoo in Port Blair)”.
In its response in late March, WII suggested that consultative meetings should be held with “select officials” to develop strategies in handling the chital population. The institute also shared a list of officials, including officers from Madhya Pradesh and Chhattisgarh forest departments, a retired forest official from West Bengal, WII scientists and independent experts from the Wildlife Trust of India, a non-profit organisation.
Besides this, WII told the Union Territory administration that capturing ungulates (hooved animals) was a “complex process” that required knowledge of the species, the diseases they suffer from, their behavioural ecology and appropriate restraint procedures.
Elaborating on the different methods available for capturing ungulates, WII said the “passive Boma capture technique has gained relevance over the years”. As per this technique, WII stated, a funnel-like fencing is used to lure herds into an enclosure that tapers into a loading chute, which helps load animals into the transport vehicle. This technique has been used to capture chital and hard ground swamp deer (barasingha) in Madhya Pradesh, Chhattisgarh and West Bengal; nilgais in Madhya Pradesh and swamp deer in Assam.
Over the years, wildlife biologists and ecologists have studied the impact of the invasive chital on local flora and fauna. Non-native flora and fauna that pose a threat of decline and elimination to local species are considered invasive. They also upset the ecosystem of local habitats by competing for resources and through predation.
These studies, done in other parts of the Andaman Islands, have all pointed out to one thing — chital are detrimental to the endemic flora and fauna. An August 2022 study on this subject, published in Biotropica, found that increasing chital presence was associated with a decrease in the density and richness of understory (shrubs that grow beneath the main canopy of a forest).
An October 2015 study on the impact of the invasive spotted deer on tropical island lizards in the Andaman archipelago found that the herbivores were a potential threat to the island’s native forest floor and semi-arboreal lizards (which live in trees). The study also inferred that spotted deer “depressed the abundance of forest floor and semi-arboreal lizards approximately five-fold, by reducing vegetative cover in the understory”.
Karthikeyan Vasudevan, chief scientist, Centre for Cellular and Molecular Biology, Hyderabad, and the co-author of 2015 study published in Springer journal, said the issue of the invasive chital needs a thorough understanding and examination, including their social behaviour and feeding patterns, on all of the Andaman islands, not just Bose Island.
Vasudevan told The Indian Express: “The spotted deer have impacted the understory vegetation. The effect on lizards is that they have lost spaces to perch and bask on. Their insect prey, which feed on certain plants, has also been impacted. This is the impact a non-native ungulate has on native flora.”