Everybody at Edinburgh Zoo is eagerly awaiting the potential arrival of giant panda cubs. Mum-to-be Tian Tian was inseminated last April, and changes observed in her hormone levels hint at a possible pregnancy. Zookeepers have started a 24-hour panda watch looking for the much-awaited signs of labour.
However, even so close to the end of her pregnancy, keepers are still not sure whether Tian Tian is really expecting, as there are no reliable pregnancy tests. And even if she is pregnant, this is still a very sensitive period as the foetus may be re-absorbed or rejected.
Breeding Pandas in Captivity: Lack of Knowledge Hampered Efforts
Panda breeding in captivity is notoriously difficult, but this is “not due to an overly complex, or maladapted reproductive biology of the species, but rather our collective lack of appreciation of reproductive mechanisms in mammals,” Dr David Kersey, from the College of Veterinary Medicine, Pomona, California tells Decoded Science. “Much of our knowledge of reproduction comes from a handful of domestic species, however, with over 4,300 mammal species, comprehension of reproduction based on less than a dozen species is merely scratching the surface.”
Initially, our lack of understanding about the biology of this species was the major obstacle to a successful breeding programme. This included not knowing how to recognise oestrous or how to handle new-born cubs, as well as a poor knowledge about the general physiology of giant pandas. “All of this seems rather simple, but collectively it had a profound impact on the lack of breeding success in captivity,” says Dr Kersey.
Captive Panda Population Explosion
In the late 1990’s and early 2000’s, the East and the West realised that it would take a major co-operative effort to conduct a series of studies to tackle these issues. “My reproductive studies were part of that effort.” says Dr Kersey, pointing out that since then, the “captive population has exploded, to the point where it is now more than double it was at that time.”
The efforts are now focussed on maximising breeding opportunities, in particular towards pinpointing with accuracy the annual brief fertility window, which stands at only 30-40h for each female. It’s interesting to think why pandas have evolved such a limited breeding period. The answer is that’s all they need in the wild. Just one oestrous per season may seem a little meagre, but “females ‘broadcast’ their impending fertility many days before it occurs.” explains Dr Kersey. “Males then compete, with the victor available to breed the female when she becomes fertile.” It wasn’t until humans came along and limited their environment that this reproductive behaviour was suddenly not enough.
Zoos often revert to artificial insemination to increase the bears’ chances for conception, “however, acting too early or too late can blow this window of fertility and we are left to wait another year for that female to cycle,” says Dr Kersey. The actual technique is not complicated, but it’s essential to time it correctly.