It was a tense night four months ago for the keepers at the Central Zoo. The resident Royal Bengal tigress, Bhunti, was in labour. They pressed their ears against the cave wall and waited. Finally, they heard muffled grunts. Three weeks later, the proud mother emerged from her den with two cubs. A couple days later, Bhunti brought out two more.

The cubs now weigh an impressive 15kg each. "They have voracious appetites," says Binab Karmacharya, the zoo's vet officer. Each cub eats 1kg of buffalo and 500g of chicken meat daily. They'll be eating a lot more very soon. The cubs' father, Jange, requires 8kg of buffalo meat six days a week and Bhunti eats 7kg.

Director RK Shrestha is confident about the cubs' survival chances: "We will try to keep them healthier than in the wild with a better diet and a less stressful environment."

As adults they won't need to fight for territory or food, reducing the chance of death from injury. A captive tiger also lives longer. In the wild, a young male tiger pushes an older one out of his territory into areas that have less prey. Unable to hunt, the tiger eventually starves to death.

Breeding tigers in captivity is very easy. Cubs can be taken from their mother right after birth and hand raised. Tigresses can then come into heat up to three times a year. Average litters have two or three cubs. That means she can produce up to nine or 10 cubs annually. So is captive breeding all good news?

"Worldwide, there are now more tigers in captivity than there are in the wild," says tiger expert Nanda Rana. Most of them are Royal Bengal tigers, which number more than any of the four other subspecies. Three other subspecies are extinct.

The primary objective of captive breeding is to keep threatened species alive with the hope of reintroducing them back into the wild. Tigers have been protected by international regulations since the 70s. By then their numbers were already dangerously low. But reintroduction poses a serious challenge, and hasn't been done satisfactorily.

There are several problems with releasing a captive tiger into the wild. Hunting is something a cub learns from its mother. In captivity, this is near impossible. In most cases the mother herself was born in captivity. And once they've had human contact, it's very difficult to release tigers that may wander into villages, endangering human lives as well as their own.

Just over five decades ago, 100,000 Bengal tigers lived in Asia. Today, there are fewer than 5,000. Some 200 of them are in Nepal. To address such a drastic decline in their population, tigers have been bred in captivity. But Bhunti's litter marks the first time a tigress gave birth in captivity since King Mahendra Trust for Nature Conservation (KMTNC) took over the zoo management in 1995.

The cubs may also find it difficult to be placed in zoos abroad since there is a glut of captive-bred tigers. Zoo experts here hope the new cubs will have some genetic value. Nine-year-old Bhunti and her 14-year-old mate Jange were both man-eaters captured in Chitwan and brought to the zoo. Since both parents are wild tigers, they feel other zoos where the Bengal tigers have been frequently inbred might make room for a Nepali tiger or two.

"We're discussing the options and we'll come to a decision soon. There is no need to rush it," says Shrestha. But space is an issue. There isn't enough room in Bhunti's lodgings at Jawalakhel for four new adolescent tigers.