Damini, who was 72, had befriended a younger pregnant elephant called Champakali at the Prince of Wales Zoo in Lucknow.

But she starved herself to death in misery when Champakali died in childbirth.

Their zookeeper is mourning the loss of his two charges. "It will take me some time to get over the death of my two loved ones," said her keeper, who goes by the name of Kamaal.

The two elephants became inseparable in September after Champakali was brought in pregnant from Dudhwa National Park where she had worked carrying tourists.

Surrogate daughter

She was in Lucknow for maternity leave, and Damini immediately became her best friend and surrogate mother.

According to animal experts, this kind of deep attachment is common among elephants, with older ones often taking a mothering role.

"Elephants are very social animals. They can form very close bonds with others in their social group," said Pat Thomas, curator of mammals at the Bronx Zoo in New York City.

But when Champakali died giving birth to a stillborn calf last month, Damini lost all interest in her food and began starving herself to death.

Zoo officials said she shed tears over her friend's body, then stood still in her enclosure for days.

Over the next 24 days she barely nibbled her diet of sugar cane, bananas and grass until her legs swelled up and she collapsed.

Grass tent

She then lay still, losing weight and crying, and a week ago stopped eating or drinking her daily 40 gallons of water, despite the hot weather.

Her keepers tried to keep her cool by building around her a makeshift tent of fragrant grass and spraying her with water.

Vets tried to save her by pumping more than 25 gallons of glucose and vitamins into her veins, but she died on Wednesday.

Kamaal has now buried her next to her friend.

"In the face of Damini's intense grief, all our treatment failed," said Dr Utkarsh Shukla, the zoo vet.