After Shuan Shuan, a female panda, returned home to Mexico following an unfruitful courtship at Tokyo's Ueno Zoo with male panda Ling Ling, zoo officials fret they may have no pandas at all soon due to worsening ties with China.</PARAGRAPH> <PHOTO> <TABLE WIDTH='200' ALIGN='RIGHT' BORDER='0'> <TR> <TD><IMG ALT='News photo' BORDER='0' SRC='/images/photos2005/nn20051105f1a.jpg' WIDTH='200' HEIGHT='153'/></TD> </TR> <TR> <TD><FONT SIZE='1'><B>Ling Ling, a 20-year-old panda at Ueno Zoo in Tokyo, watches visitors from his pen. </B></FONT></TD> </TR> <TABLE> </PHOTO> <PARAGRAPH>Breeding staff at the zoo say that whereas 18-year-old Shuan Shuan was quite bold, the timid 20-year-old Ling Ling was so scared of her that they had no chemistry. Artificial insemination attempts also failed.</PARAGRAPH> <PARAGRAPH>'I feel as if an era has ended,' said zoo veterinarian Fumitaka Hashizaki, 57.</PARAGRAPH> <PARAGRAPH>In 1972 Lan Lan and Kang Kang were donated to the zoo by China as a symbol of friendship between the two countries. The day they made their public debut, visitors waiting for a glimpse formed a line stretching 2 km long. That year 7 million people visited the zoo, sparking a nationwide panda boom.</PARAGRAPH> <PARAGRAPH>After the two pandas died, China sent Huan Huan and Fei Fei, and they had three cubs -- Chu Chu, Tong Tong and You You. Ling Ling was also sent to the zoo, which now receives about 3 million visitors per year.</PARAGRAPH> <PARAGRAPH>But the pandas have since either died or been transferred to other zoos and now there is only Ling Ling, who is showing his age. Pandas have an average life expectancy of about 25 years, and the death rate rises after they turn 20. If Ling Ling dies, the number of visitors to the zoo is expected to plummet.</PARAGRAPH> <PARAGRAPH>Pandas are threatened with extinction and China stopped donating them to foreign countries in 1982. Fei Fei was the last panda allowed to leave the country.</PARAGRAPH> <PARAGRAPH>In an exception to the restriction, China is preparing to donate a panda to Taiwan, but doing the same for Japan would be difficult because relations between Japan and China are at their worst in decades.</PARAGRAPH> <PARAGRAPH>Like Oji Zoo in Kobe, Ueno Zoo could pay to rent a panda from another zoo, but according to a zoo official, the rental fee is more than 100 million yen per panda.</PARAGRAPH> <PARAGRAPH>Ueno Zoo is pinning its hopes for a new panda on artificial insemination in Mexico using frozen sperm donated by Ling Ling. But even if artificial insemination is successful, Ueno Zoo would only have the right to a second and subsequent cubs.</PARAGRAPH> <PARAGRAPH>'We would like to continue to help breeding in Mexico,' said the head of the zoo, Teruyuki Komiya, 57.</PARAGRAPH> <PARAGRAPH>Yoshiaki Sagawa, who has been caring for Ling Ling for more than five years, said, 'If you see –

every day, you can understand their daily physical condition by how they look,"

Ling Ling is now going gray. "He is losing his appetite due to his advanced age," Sagawa said. "If the price of his favorite -- persimmons -- falls, I would like to give some to him."