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Sunday, April 8, 2012
Procreation begets problems for pandas
By ROWAN HOOPER
Just how cute are giant pandas? The public can't get enough of them. The star attractions at Ueno Zoo in Tokyo are Ri Ri and Shin Shin, a male and female pair who helped attract some 4.4 million visitors last fiscal year — the highest number for 19 years.
Ueno Zoo certainly needs the money they generate. To host a pair of pandas, foreign zoos must pay the Chinese government at least $500,000 per year for 10 years. Rich countries such as Japan pay more like $1 million. However, the animals remain the "property" of China, which means that if something goes wrong — a panda dies unexpectedly, for example — the foreign zoo has a lot of explaining to do to the Chinese.
This happened in 2010, when Xing Xing, a 14-year-old male, died a grizzly death at Prince Zoo in Kobe City. The animal, also known as Kou Kou, was anesthetized by keepers preparing to collect sperm to use in artificial insemination. Unfortunately, Xing Xing vomited gastric fluid, breathed the acidic mixture into its lungs, and suffocated. Kobe City had to pay $500,000 compensation to China.
But even when not coming to an untimely end, giant pandas can still be remarkably frustrating. Indeed, they seem to have gone out of their way to make things difficult for themselves.
Females, for example, spend less than 1 percent of their year devoted to sexual activity. They only have a brief period of estrus, once a year, lasting one to three days. Miss that window in Spring, and it's another year before they can have meaningful sex again.
That, by the way, is meaningful in a different sense from how humans might understand it. Male pandas have penises that are short in proportion to their body size, which means that copulation has to be conducted with a certain amount of care and precision to have a chance of success.
These are some of the reasons that researchers and zookeepers try so hard to get pandas to breed in captivity — and have to undertake such risky procedures as anesthetizing animals to collect sperm.
Hardly anyone outside China has managed to breed giant pandas, and by far the most successful captive breeding is done at the Chengdu Research Base of Giant Panda Breeding in Sichuan Province. In 2010, the Research Base announced that it had bred its target of 300 pandas.
It's come a long way. When I visited the place in the late 1990s, I was shocked at the conditions. The state of panda conservation, I thought, was summed up pretty well by Lai Lai, a female lying on her bench in her concrete cell lapping up vomit that she kept retching up.
I counted 11 stuffed pandas in the museum attached to the breeding centre, plus fetuses preserved in jars and a few skeletons. There were eight living pandas in the grounds.
By all accounts those days are over. Some critics, however, say that breeding them is one thing, but animals must be returned to the wild — and more must be done to preserve their dwindling habitat. The International Union for Conservation of Nature (IUCN) still classifies giant pandas as endangered on its Red List, and China says it is now considering a serious program of reintroduction.
I spoke to Henry Nicholls, author of "The Way of the Panda" (Profile Books, 2010), which charts the entwined fortunes of pandas and China over the last 140 years. He was unsure about the conservation value of China's plans to reintroduce pandas to the wild.
"Reintroduction is a vastly expensive distraction with the primary purpose of providing moral justification for huge and lucrative breeding centers," he said. "They are serious about it. But it doesn't do much to save pandas."
In the wild, pandas — which don't hibernate — live in the mountains of Sichuan, and also Shaanxi and Gansu provinces. They used to live in the lowlands but have been driven into the highlands by humans. They eat, as everyone knows, bamboo. That would be fine except that they are bears — which are carnivores — and they are poorly adapted to a diet of 99 percent bamboo. They rely on gut microbes to digest the plant material, but still need to munch through up to 20 kg per day.
With all those difficulties surrounding the daily and the reproductive lives of giant pandas, it is now good to hear that a three-year study of pandas at the Chengdu center aims to improve our understanding of the males' reproductive system and, say the researchers, assist in reintroducing pandas into the wild.
Although biologists knew that females had only a really narrow window of sexual receptivity, very little was known about males.
Now, Copper Aitken-Palmer of the Smithsonian Conservation Biology Institute, Rong Hou of the Chengdu Research Base of Giant Panda Breeding, and colleagues, have found that male giant pandas are a little bit more willing and able to mate than females.
The team evaluated the seasonal changes in androgen ("male" hormone) levels of eight male pandas, and also looked at sperm concentration, testes size and reproductive behavior. They found that, unlike females, reproductive activity in males comes in waves, occurring three to five months before the interval when most females ovulate.
The researchers suggest this is in order to prepare for and then accommodate the brief and unpredictable female. So how can it help? Well, Aitken-Palmer's team believe the findings can be used to help collect and preserve only the highest-quality panda spermatozoa for artificial insemination.
Interestingly, meanwhile, the team — whose research report is published in the journal Biology of Reproduction (DOI reference: 10.1095/biolreprod.112.099044) — found a similarity with the Japanese black bear, although it's unlikely to be one that gets any publicity at Ueno Zoo: The giant panda is the only other species of bear that stops making sperm altogether in August.
Rowan Hooper (@rowhoop onTwitter) is the News Editor of New Scientist magazine.The second volume of Natural Selections columns translated into Japanese is published by Shinchosha at ¥1,500. The title is "Hito wa Ima mo Shinka Shiteru (The Evolving Human)."