Earlier this month, a zoo in China reported a rare birth of panda triplets. Pandas are notoriously difficult to reproduce in captivity; therefore, this success excited people worldwide, particularly those working in other zoos that have them on expensive loans from China. One such example are the experts at the Edinburgh Zoo.They finally had the success of impregnating the only female panda in U.K., Tian Tian, this year. They are now expecting the panda to give birth on Aug. 31. Human fertility techniques have proven to be critical in these successful panda reproductions.
Female pandas have only a few days open to mating and the fertility window is less than 36 hours. In the wild males fight for the mating rights during their annual gathering season of April and May. Younger ones have the opportunity during these two months to watch the mating process and learn.
However, in captivity, there are only a few male pandas out of hundreds of pandas, overall, who are on loan to participate in the natural reproduction process. Even if a male panda is available, there can still be problems of the panda not showing enough interest and willingness. Experts have speculated that the lack of competition or more important, the lack of know-how, are the reasons.
The captive environment may also have impacts on the female pandas. Edinburgh Zoo reported that Tian Tian rejected the mating attempts of Yang Guang so violently that they had to be separated for safety concerns.
In order to overcome such difficulties in captivity, artificial insemination (AI) proven to be successful in humans, has been used and has resulted in great success with pandas, as well. Also, a deepening understanding of the biology and behaviors of pandas, which experts gained in recent decades, are critical. Hormone levels in the urine of female pandas are closely monitored to predict the most fertile time. When the optimal moment comes, the female is sedated and a semen sample, fresh or previously frozen and thawed, is inserted into the female and released in the cervical canal.
Male pandas are anesthetized for stress reduction and procedure safety, when undergoing the electro-ejaculation process, in which several pulses of an electrical stimulus are applied to induce ejaculation. The insemination procedures for female and the semen collection procedures are relatively non-invasive and both sexes are usually “back to normal” within a few hours.
Panda semen is proven to be quite resilient—it remains viable for fertilization after being frozen (cryopreserved) and thawed. This enables its long-term storage and is vital for reviving this endangered species. Panda breeding facilities around the world can swap semen samples, use samples from decades ago, and collect semen from wild populations to help pandas reproduce using human fertility techniques. This way, genetic diversity can be maintained and inbreeding depression can be avoided.
Unlike human females whose success of conception after insemination can be predicted after a precise time window (positive if no menstruation after 14 days) and can be easily confirmed via ultrasound, the success in female pandas is more difficult to determine. First, pandas experience embryonic diapause, which means a fertilized embryo not yet implanted in the uterine wall. While the gestation period is fixed at about 50 days, the pregnancies can be more than 160 days because of this.
Second, female pandas can also experience pseudo pregnancy, in which they exhibit the same behaviors as pregnant pandas even when they are not. Their hormones can even show similar changes. The ultrasound is useless since panda fetuses are often too small to be spotted.
In the wild, female pandas usually gives birth to twins, but are only able to care for one. The other one is left to die. In the breeding facilities, while the panda mother cares for one baby, experts armed with a wealth of accumulated knowledge take care of the other one. The babies take turns at being cared for by the panda mother and the zoo personnel. The survival rate of panda babies born in captivity has increased to around 90 percent in recent years.
Their natural habitats of temperate broad-leaf and mixed forests of Southwest China in the Yangtze Basin were fragmented due to roads and railroads, causing population separation. That is one of the factors negatively affecting panda reproduction in the wild. The reduction of bamboo supply, which is the pandas’ food source, has also contributed to their being an endangered species.
Among the many organizations working with China to conserve pandas is the World Wildlife Foundation (WWF) whose logo is a panda. WWF has focused on linking isolated panda populations by creating green corridors, protecting the habitats by patrolling against illegal logging and encroachment of development and forging a better relationship between local communities and pandas.
Human fertility techniques also have seen great success to boost the populations of endangered cats, among other species, in addition to helping pandas reproduce in captivity. There are many people wondering about the value versus the cost of such expensive and individual-focused approaches in species conservation. For the limited resources available that are earmarked for conservation efforts, more debates are expected on the value of individual-focused approach as compared to the value of habitat protection.
By Tina Zhang