TAIPEI - Zoologists in Taiwan have artificially inseminated a panda presented by the mainland on Saturday, a move that they believe has the highest chance of reproductive success for the sex-shy animal.

Panda experts from Taiwan and mainland collected sperm from Tuan Tuan, a male panda, and used it to artificially inseminate his female companion, Yuan Yuan, after zoologists found the female panda was sexually active on Friday evening.

Examination has showed Tuan Tuan's sperm is potent enough. However, because pandas have small fetuses, experts have to keep using ultrasound equipment to make sure whether a female is pregnant, according to spokesman with the Taipei Zoo, home to the panda pair.

The two pandas were deliberately enclosed together on Friday evening. Previously, they were put in separate cages because familiarity with each other may make the animal feel as if they are a brother-and-sister pair.

Scientists decided to resort to artificial insemination after they found Yuan Yuan seems to show little interest in his lustful partner.

Tuan Tuan and Yuan Yuan - whose names together mean "reunion" in Chinese -- were sent to Taiwan by the mainland as goodwill gifts more than three years ago. Though the pair had went into heat previously, they failed to reproduce any cub.

Pandas usually go into heat from March to May each year. A female panda's pregnancy usually lasts for 120 days to 150 days. The shortest panda pregnancy on record lasted for 70 days and the longest for 324 days.