…continued from “The Problem with Pandas – Part 1”
It has turned out to be enormously difficult to breed pandas in captivity, a feat not accomplished at all until 1963. Where’s the problem?
Why not just put a male and a female panda together and let them get on with it?
Firstly, the female panda only comes into heat once a year, for about three days, during which she is only fertile for 12 to 24 hours. However, this fertile period can be detected by testing her urine. Then, most attempted romantic encounters proved very disappointing. The male has a very short penis, so that accurate positioning is necessary, and they are not very good at doing this. Moreover, preliminaries in the wild involve fighting among males for the privilege of mating, and this seems to be an important part of the arousal process. So despite measures ranging from sex education videos, to stimulating the males with sticks of bamboo carrying the female scent, to the use of Viagra, managed encounters in the zoo often end in disappointment or even violence.
The present successful breeding program in China uses artificial insemination (don’t ask!). However, that doesn’t put an end to the problems. Pandas very often display pseudo-pregnancies, quite difficult to distinguish from the real thing, even by hormonal testing. Ultrasound can be helpful here, but requires considerable skill because of the smallness of the foetus, as well as the corporation of the animal. (The mother weighs around 100 kg or more; the new-born offspring, a mere 100g.) Like other members of the bear family, pandas show delayed implantation of the foetus, and as a result, actual pregnancies can range between 11 weeks and 11 months. Because of the small size of the foetus, and the complications of pseudo-pregnancy, true pregnancies do not become obvious until shortly before birth.
Pandas usually give birth to two clubs at a time, but only care for one. This is thought to be because pandas lack the ability to build up reserves of fat, leaving the mother unable to make enough milk for two. So the expert panda breeders at the world’s leading centere in Chengdu have resorted to trickery, caring for the abandoned cub in an incubator, swapping the two clubs around when their mother wasn’t paying attention, and supplementing the mother’s milk with imitation bear milk. Both cubs do, however, need their share of mother’s attention. They have weak immune systems, so they rely on antibodies in their mother’s milk. They also need help in defecating, which the mother supplies by stroking their lower abdomens with her tongue. However, this particular problem clearly resolves itself by adulthood, since a full-grown panda makes 40 panda-pats a day.
The panda breeding programme is big business, with the Chinese retaining ownership of the beasts, and renting them out to Western zoos for $1 million a year. This is over and above the cost of looking after them. Even so, the programme has been so successful that centere-bred pandas are now being reintroduced into the wild. Suitable habitat has been bought, and will no doubt in due course be a major attraction for eco-tourists. Keepers involved in the reintroduction have been dressing up as pandas, so that their charges will feel more at home when released. However, critics of reintroduction point out that the entire exercise is meaningless unless these pandas are being provided with enough protected habitat, and it was recently announced that the first released panda had died after only a few months in the wild.
Polar bears have many things in common with pandas. They are favourites at the zoo, carry strange secrets in their genes, and are adapted to a very specific shrinking habitat, with all that that implies.
Polar bears really are bears, not just members of the same extended family, having diverged from brown bears by a process of peripatric speciation (new species forming by adapting to conditions on the fringe of the species’ range). But an unexpected fact is concealed in their mitochondrial DNA. They are all descended on their mothers’ side from extinct giant Irish brown bears, although this is best attributed to cross breeding between established species, rather than to late emergence of polar bears as a separate population. During the million years that they have existed as a (more or less) separate species, polar bears have adapted their range to climate, and roamed as far south as the Thames Valley during the ice ages. What is going to happen now, as their preferred habitat on the land – sea ice boundary simply ceases to exist, is quite another matter. The London-based Daily Telegraph, which vacillates between simple global warming denial, and claims that warming is good for you, tells us that they are thriving, although the purely local increase in number that they report is known to be the result of restrictions on hunting. Early breakup of the ice makes it more difficult for polar bears to find food, leading to an increase in their attempts to steal food from humans. The inhabitants of Churchill, on Canada’s Hudson Bay, have built a polar bear jail, where nuisance bears, under sedation from rifle-fired darts, are held before being transported to the wild. Global warming has led to the bears coming ashore a week earlier per decade, increasing the length of time during which the mother must feed herself and the cubs she is carrying from her accumulated fat reserves. This is already affecting numbers, and further lengthening of the starvation period is expected to lead to smaller litters, and decrease survival chances for each cub.
Under business as usual, polar bears are in real trouble. So are we.
Paul Braterman is on the committee of the British Centre for Science Education. His next book, From Stars to Stalagmites, will be published next May by World Scientific: http://www.worldscibooks.com/popsci/7953.html