The Smithsonian's National Zoo's giant panda mating season began earlier than expected again this year. Female Mei Xiang (may-SHONG) and male Tian Tian (tee-YEN tee-YEN) attempted to mate Saturday, Jan. 9.
It appears a new January ovulation pattern is emerging for Mei Xiang; excluding 2009, typical ovulation for her has historically occurred in March or April.
Over the course of a few hours, Zoo staff carefully observed the pandas' activities and, because competent mating did not occur, Zoo scientists and veterinarians performed a nonsurgical artificial insemination later that evening and again this morning. Both pandas were anesthetized, allowing the scientists to collect semen from Tian Tian and insert it directly into Mei Xiang's uterus.
Giant pandas have one very brief breeding season each year, with only a day or two of actual mating. The early start of these past two seasons is unusual, but the expertise of the Zoo's staff enabled them to immediately identify signs of this early reproductive activity and prepare for a possible artificial insemination.
Early last week, the Zoo's animal care team noticed Mei Xiang exhibiting signs of an early estrus, including distinctive vocalizations that are associated with mating season. Staff immediately began monitoring the hormone levels in her urine, which allowed them to predict the exact moment she had ovulated. Timing is crucial—female giant pandas only have about one day a year in which conception can occur.
There is no conclusive study that indicates what causes panda ovulation. Although scientists know that giant pandas mostly breed in late winter to early spring, it is not known if the onset of reproductive activity is triggered by increasing day length, temperature or some other environmental factor.
Zoo staff separated Mei Xiang and Tian Tian before performing the artificial insemination. They will remain separated for the next few months, until Mei Xiang either delivers a cub or Zoo scientists determine that she is not pregnant. Keeping the pandas separated will reduce the risk of increased stress-hormone levels in Mei Xiang, which could jeopardize a developing embryo. Panda gestation typically lasts from 90 to 185 days. Veterinarians and scientists will monitor Mei Xiang's hormone levels and perform ultrasounds to determine if she is pregnant.
Last year, scientists artificially inseminated Mei Xiang, but she did not give birth. Mei Xiang and Tian Tian have produced one cub, Tai Shan (tie-SHON), who was born July 9, 2005, as a result of artificial insemination.
TAI SHAN DEPARTURE UPDATE: Tai Shan is scheduled to leave for China, per the Zoo's agreement with the Chinese. Transportation plans are being finalized but the departure date has been narrowed to early February. Friends of the National Zoo will host a public farewell event for Tai Shan Saturday, Jan. 30, from 11 a.m. to 3 p.m. Visit http://nationalzoo.si.edu for details.