Deteriorating conditions prompted rights group People for the Ethical Treatment of Animals last month to sue states running zoos and the Central Zoo Authority that oversees them.
"From August last year till March this year we compiled our own inventory of zoos," said PETA's director Anuradha Sawhney.
The group discovered animals, including elephants, were kept chained or shackled, nocturnal animals were kept in bright sunlight, aquatic animals were kept in inadequate water and teasing was rampant.
"You have visitors giving animals all kinds of things to eat, giving the monkeys lit cigarettes, glass, pakoras (vegetable fritters)," she said, adding that PETA was suing the bodies for inflicting "pain and suffering" on animals and noncompliance with local zoo regulations.
Zoo officials themselves acknowledge that such problems, particularly harassment by visitors, are common in urban centres around the country.
At the 131-year-old zoo in the eastern Indian city of Kolkata, many enclosures