A representative image of a tiger crossing trails in the B.R. Hills forest. Photo: Anup Hela/Wikimedia Commons.
On July 29 – International Tiger Day – a press note from the field director of Kali Tiger Reserve (KTR) had two exciting details. One, photographs of a tiger showed that it had dispersed over a distance of 215 km; two, that there has been an exponential growth in the number of tigers over the last two years.
The quadrennial All India Tiger Estimation of 2018 pegged the number of tigers in India at 2,967. There may not be much room for celebration here because most tiger reserves are currently threatened by infrastructure development projects like roads, power lines and railway lines. Such intrusions continue to shrink and fragment tiger habitats.
A genetic study of tigers across India showed tigers are becoming more isolated, which in turn reduces tigers’ chances of finding a mate who is not closely genetically related, thus lowering the genetic variation and increasing the risk of extinction. Most tiger populations in India are small, secluded in protected areas and hence unviable. Therefore, it may not be effective to take a protective approach with large carnivores inside protected areas.
A tiger named T-31
But as long as there are corridors for tigers to move between protected areas, they have been known to disperse over long distances, even through human-dominated landscapes. Typically, one-and-half to two-year-old tigers move from their natal range in search of new territories.
Two decades of camera-trapping studies undertaken by the Centre for Wildlife Studies and the Wildlife Conservation Society (India) in the Western Ghats of Karnataka have revealed multiple instances of tigers moving between protected areas. (Editor’s note: The author was involved in these activities during his affiliation with these two organisations.)
During their 2008 camera-trapping survey in KTR, researchers reported the first case of long-distance dispersal. A four-month-old cub spotted in the Bhadra Tiger Reserve in 2006, so named BDT-130, was again photo-captured as an adult male in the core area of KTR. The radial distance covered in that case was 200 km, and the dispersal route was likely through a known wildlife corridor between Sharavathi valley and KTR.
Since 2015, the Karnataka forest department has been conducting camera-trap studies in KTR, adopting a monitoring protocol that the National Tiger Conservation Authority and the Wildlife Institute of India have standardised. In May 2020, a tiger designated T-31, first spotted in the Sahyadri tiger reserve in Maharashtra in May 2018, was photo-captured in KTR. This is an approximate distance of 215 km, as the crow flies. As such, this is the second recorded case of a tiger immigrating into KTR, which in turn seems to be emerging as an important source population for tigers in the connected landscape of North Karnataka-Goa-South Maharashtra.
During the camera-trapping survey at KTR in March-May this year, officials photo-captured 22 uniquely identified adult tigers, 12 of which were female. “This is an exponential rise in the number of tigers in the past two years, and we have got a good gender ratio, which generally is seen in stable populations,” field director of KTR Maria Christu Raja D. told The Wire. “It is too early to say much about this sudden increase in tiger numbers within KTR. I believe the phase IV survey in 2021 will only confirm how stable this population rise is.”
Raja also said KTR is planning an exercise – in which officials will pattern-match the tigers from all protected areas adjacent to KTR. “We are likely to find that there is regular movement of tigers between KTR, Bhimgad wildlife sanctuary in the north and protected areas of Goa in the west.” These areas make up a contiguous forested area of over 10,000 sq. km – an ideal place for supporting a genetically viable tiger population.
The conservation of genetically connected populations requires a forest corridor between protected areas and which are protected by law. On June 23, the Maharashtra government took an important step in this direction by declaring 29.53 sq. km of Dodamarg forest range in Sindhudurg district to be the Tillari Conservation Reserve.
Girish Punjabi, whose work at the the Wildlife Conservation Trust focuses on forests along the three-way junction of Maharashtra, Goa and Karnataka, said, “The recent dispersal event of T-31 from Chandoli national park to KTR proves that this corridor” – which he called “very critical” – “is functional and needs the utmost protection.”
Karnataka’s wildlife corridors
Forests in the Western Ghats, starting from the Karnataka-Kerala-Tamil Nadu junction until KTR in the north and adjoining forests of Goa, have an estimated 1,000 tigers. The Western Ghats landscape has connecting forest corridors between various protected areas and conservation reserves, across which mega-fauna like tigers can disperse with ease. These 1,000 tigers are identified as being part of a single Western Ghats ‘genetic cluster’, and the respective populations have good genetic variation.
Contrast this with the northwestern cluster, consisting of a single population in Ranthambore tiger reserve in Rajasthan, where tigers have no corridors connecting them to the nearest populations, in Central India. Since this population is genetically isolated, it doesn’t have the ability to quickly develop defences against new diseases and similar natural causes, and has a high probability of being wiped out.
The long distance dispersal of tiger BDT-130 from Bhadra Tiger Reserve to KTR was possible because of the corridor between the Bedthi Conservation Reserve and KTR. However, this corridor is now at risk of being destroyed by the proposed Hubballi-Ankola railway line, which will cut through. It already defies logic to dissect such an important pathway between a conservation reserve and a tiger reserve.
This is why the Karnataka government should review its controversial decision to okay the project proposal. Instead, it should take its cue from the Maharashtra government and further protect the corridor through which BDT-130 dispersed. Protecting forest connectivity in this landscape will go a long way towards India retaining its proud status as the home of so many of the world’s tigers.
Narendra Patil has worked for the Wildlife Conservation Society (India) and the Centre for Wildlife Studies for a decade, and with the Snow Leopard Conservancy (India Trust) in Ladakh for two years.