The fence ran right along the road. A hillock rose on our left and to our right were vast empty drylands. The earth crackled underfoot in the midday sun.

The fence was the boundary of the Vallanadu Blackbuck Sanctuary in Thoothukudi district in Tamil Nadu. It is the southernmost part of India that has a population of this endemic species of antelope. The blackbucks we were observing from a high watchtower inside the sanctuary were, however, outside this border.

Even though the sanctuary was created for these blackbuck herds, the habitat inside the sanctuary is not suited to them. The 14.6 square kilometre protected area is situated on a group of hillocks in an arid area that is dominated by thorny scrub vegetation. The scrub is too dense for an animal the size of a blackbuck to pass. Blackbucks are known to prefer open habitats, mainly grasslands and do not use the dense vegetation of acacia trees. “No wonder they are seen on the highways here," said Prashanth MB, part of a group of researchers at Atree, a conservation research organisation in Bangalore, that has studied the sanctuary for blackbuck population density. "The fence protects the area except that it keeps them outside. The grasslands that the blackbucks need are actually outside the sanctuary.”

According to the Atree study, which was published in Indian Forester, it would make sense to clear the sanctuary of some of its exotic species to make way for grasslands that would ensure that the animals move inside. The study also showed that instead of blackbucks, the sanctuary is dominated by feral dogs and cows, which compete with wild herbivores like blackbucks and sambar deer for forage and water. Chandran, the forest watcher who was walking with us, pointed us to cattle traps that they had set up. “Oddly, it has turned into a cattle sanctuary and not blackbucks," said Prashanth.

Right outside the fence, a big sign looms, over a large area of land cookie cut into smaller pieces for apartment buildings. The sign reads “Golden Mega Town”. Just about 16 kilometres away from Tirunelveli town, the real estate sector is starting to notice this area. A few hundred metres away, the blackbucks forage in a degraded grassland patch next to a water body. Around the other edge of the sanctuary are quarries which further drive them towards the road. There is no buffer zone. The blackbucks are stuck between a four-lane highway and realty boom.