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Treating China's notoriously undersexed national icon to “panda porn” - or videos of other pandas having sex - is believed to have had some success. Now China has devised a new tactic to help the black-and-white animals to have more babies.

The answer is “sexercise”. Keepers are putting their charges at the Chengdu Panda Breeding and Research Centre in southwestern Sichuan province through a rigorous programme with the aim of improving their mating skills.

It involves apples. An apple is dangled from a string above the panda, luring it to stand on two legs as it tries to reach the treat. The exercise helps the panda to walk on its rear legs, thus strengthening the pelvic and hip muscles and better equipping it for sex.

Yang Kuxing, keeper of ten pandas in the centre's maternity ward, said that sexercise should aid the males when mating: “After pandas succeed in taking the standing-up exercise, we feed them apples to reward them.”

Such quirky measures are designed to ensure the survival of one of the world's most endangered animals.

China said last November that it had 239 pandas living in captivity with another 27 living overseas. A total of 1,569 are believed to live in the wild and remote corners of the south west of China.

But the keepers are relying on more than pornography and dangling apples to improve the sexual skills of the panda.

Pandas are solitary animals in the wild and seek companions only during the mating season. Keepers are trying to familiarise pandas, which have often been bred in captivity, with members of the opposite sex.

A male panda is placed in a den occupied by a female, and vice versa, so that they smell each other's odour.

With any luck, they may begin to show an interest in sex, often seen as symptoms of anxiety. The two are then placed in the same pen in the hope that they will have sex.

Pandas with a bit more experience may also be called in to help their more innocent companions. One official said: “We arrange lovemaking between two excellent pandas in front of inexperienced pandas which have never had sex. It does work.”

Now more than 30 per cent of the 68 pandas at the base are capable of having sex naturally compared with just 10 per cent a decade ago.

China is desperate to ensure that it has a sufficient number of pandas, with a broad genetic variety, to ensure the survival of the species.

Keepers try to ensure that all pandas can find a mate as soon as they “come into season” - when the female is fertile and receptive. This state lasts only a few days.

In addition to being encouraged to have sex with a willing male, the female is then artificially inseminated to reduce the room for failure, experts say.

The procedure, which involves giving the male mild electric shocks to obtain sperm, and the female an anaesthetic while she is impregnated, can be uncomfortable and traumatic, some experts say.

Also, genetic tests have found that the natural mating has usually been successful in any case.

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