The Nallamala Hills: Home to India’s Largest Tiger Reserve

1.1 Where are the Nallamala Hills, and what do they hold?

The Nallamala Hills are part of the Eastern Ghats, mainly in Andhra Pradesh and Telangana. They host the Nagarjunasagar-Srisailam Tiger Reserve, known as NSTR.

• NSTR is India's single largest tiger reserve, covering about 3,728 square kilometres.
• The Krishna River flows through the reserve for around 270 kilometres.
• The hills run mainly north-south, forming a long ridge line across two states.
• NSTR spreads across five districts: Nandyal, Prakasam, Palnadu, Nalgonda, and Mahabub Nagar.
• Three of these districts lie in Andhra Pradesh and two in Telangana, since the reserve straddles both states.
• The Srisailam Dam, on the Krishna River, sits inside the reserve itself.
• The dam generates hydroelectric power and supplies irrigation water to both Andhra Pradesh and Telangana.
• It is one of the largest masonry dams in the world, built directly across a deep gorge on the Krishna.
• The reservoir behind it also supports drinking-water needs for towns across both neighbouring states.
• The hills take their name from the Telugu word for a creeper-covered range, "Nallamala" meaning black forest.
• They form part of the wider Eastern Ghats, a broken, discontinuous range unlike the continuous Western Ghats.
• Average elevations in the Nallamala Hills run from about 520 to 700 metres above sea level.
• The range stretches roughly 430 kilometres, from the Krishna River in the south to the Godavari River area further north.
• Locally, different stretches of the range carry their own names, including the Yerramalas and the Velikonda range.
• Rainfall here is moderate, arriving mostly from the retreating northeast monsoon rather than the summer monsoon.

2.1 What does the terrain and wildlife look like here?

The terrain includes plateaus, ridges, gorges, and deep valleys. The forest type is tropical dry deciduous, with an undergrowth of bamboo and grass.

• The reserve is home to around 74 mammal species and 302 bird species.
• Predators found here include the leopard, wolf, Asiatic wild dog, and Indian pangolin.
• Srisailam, a major Jyotirlinga pilgrimage site, sits within the reserve's boundary.
• The reserve holds a genuinely huge Critical Tiger Habitat, the largest of any reserve in India.
• Several thousand families still live inside the reserve's core area, in villages predating the reserve itself.
• The reserve was formed by merging two older sanctuaries, Nagarjunasagar and Rajiv Gandhi Wildlife Sanctuary.
• It falls under Project Tiger, India's flagship tiger-conservation programme launched in 1973.
• Chenchus, a designated Particularly Vulnerable Tribal Group, live traditionally within these forests.
• They have traditionally practised hunting and gathering, alongside limited shifting cultivation on the hills' slopes.
• The terrain's ridges and gorges make parts of the reserve difficult to access, helping shield its core habitat.
• Andrographis nallamalayana grows only here, an endemic medicinal plant named directly after the hills.
• The reserve's dry deciduous forest turns notably green during the southwest monsoon, from June to September.
• Sloth bears, four-horned antelope, and mouse deer also live within these forests, alongside the reserve's tigers.
• Rock formations across the hills also shelter ancient cave paintings, evidence of long human presence in the region.

3.1 What's the exam trap here, and what else is worth knowing?

The region also holds several endemic plant species, found nowhere else on Earth, including Andrographis nallamalayana.

• Despite being India's largest tiger reserve by area, NSTR remains far less publicly known than Ranthambore or Jim Corbett.
• This is a useful exam contrast: being the largest reserve doesn't automatically mean being the most famous.
• Amrabad Tiger Reserve, just across the border in Telangana, was once part of the same undivided reserve.
• The two reserves were split administratively after Telangana's formation in 2014, though they remain ecologically connected.
• NSTR's Eco-Sensitive Zone has been formally notified, one of only 29 tiger reserves nationally with that status.
• A proposed National Highway upgrade through the reserve raises real habitat-fragmentation concerns for planners.
• Railway lines already cross parts of the reserve, prompting proposals for wildlife underpasses and fencing.
• Invasive plants like Lantana camara and Prosopis juliflora are actively managed here through annual weed removal.
• NSTR has identified fringe forest areas for the Green Credit Programme, a Union government afforestation initiative.
• The programme invites voluntary participation from government agencies, PSUs, and private organisations to restore degraded land.

4.1 What did the 2026 STRIDES report find?

NSTR has 4,700 families across 17 villages still living inside its notified Critical Tiger Habitat. (Source: The New Indian Express, July 15, 2026)