For generations, trainee officers in the Indian Army faced a legendary test of their jungle survival skills: the rite of capturing, killing and eating a snake, preferably a highly venomous one, to prove they had conquered their fear of the wild.

Now, however, a steep decline in the snake population – and fear of upsetting animal lovers – has forced students of the infantry's commando training wing in the southern state of Karnataka to forgo serpentine sources of sustenance.

Instead, they are being sent on exercises with extra rations of chocolate, dried fruit and nuts.

One officer who recently completed the gruelling 45-day commando course said: “Snake was still on the menu, but the school now has to use captive-bred animals and it's limited to one per class, so you just get a bite. It was chewy – a bit like mutton.”

The shortage of snakes threatens to deprive the army of one of its most effective training tools, according to Brigadier B.K. Ponwar, the head of the Indian Counter Terrorism and Jungle Warfare College. He told The Times: “Feed a snake to a soldier and it gets the fear out of him. It's part of the process of teaching the soldier that the jungle is his friend, and that one of his best friends is the snake.”

There are no accurate figures available for the number of snakes in India. There are 270 species, more than 50 of which are poisonous – with 11,000 Indians dying from snake bites every year – but it is widely believed that numbers have fallen sharply over the past 60 years, during which the country's human population has tripled.

“Human encroachment on natural habitats is the primary concern,” Samir Sinha, the head of Traffic India, the conservation group, said. “As the country becomes more urbanised, the skills needed to live alongside snakes are dying out. The first reaction of more and more Indians is to immediately kill any snake they see.”

Changes in farming patterns, such as the switch from rice paddies to cash crops such as cotton, have added to the destruction of habitats, while iconic species such as the cobra have fallen prey to poachers and snake charmers.

Many soldiers will be happy to see the end of the snake-eating tradition. Brigadier S. K. Chatterjee, of the army's public information directorate in Delhi, said that he went through the process of finding, killing and roasting a snake as a young man 30 years ago, but chose to forgo the eating part.

“Of course, it's essential to be able to live off the land,” he said. “But there are more calories in a chocolate bar.”

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