A faked pregnancy sounds like the plot of a TV soap opera, but plans to have a live broadcast of the birth of 6-year-old giant panda Ai Hin's cubs had to be called off earlier this week when the Chengdu Giant Panda Breeding Research Center discovered that she was in fact not actually pregnant.
Arguably, there's something innately appealing about the thought of an adorable panda tricking researchers into thinking she's pregnant so she'll be able to eat all the fruit and bamboo she wants. However, it's more likely that Ai Hin was simply experiencing a phenomenon known as pseudopregnancy. Pseudopregnancy occurs when females exhibit the biological signs of pregnancy, including a decrease in activity and an increase in appetite, even though they are not pregnant. In some cases, they may even experience physiological changes to the genitalia.
Pseudopregnancies are difficult to diagnose in pandas because a female panda experiencing a pseudopregnancy will also show a rise in progestins in her urine, just as she would if she were actually pregnant. A female panda with a pseudopregnancy is not having a faked pregnancy; her body is behaving as if she really were pregnant. All of the signs are there, except an actual fetus.
Researchers hypothesize that pandas may be prone to pseudopregnancy because of their unique reproductive cycle. A wild panda typically lives about 20 years and is not fertile until she's at least five years old. Panda cubs gestate for about 50 days, but pandas only mate once every two or three years while raising a cub in between. In a way, a pseudopregnancy helps prepare female pandas for the "real" thing -- thus helping to ensure that they'll be prepared when a cub really does arrive.
If you're wondering why researchers didn't discover the faked pregnancy with an ultrasound, the answer is simple. A giant panda fetus is extremely small and quite difficult to find with an ultrasound, which is how a similar case happened in 2010 at the Smithsonian National Zoo. Giant panda Mei Xiang had elevated levels of the progesterone, slept a lot, and built bamboo nests, but was not actually pregnant.
Pseudopregnancy isn't just limited to pandas, so you might want to be suspicious if your pet sudden starts acting like she's pregnant. Female cats and dogs both experience this condition, which is thought to be caused by an imbalance of progesterone and prolactin. Pseudopregnancy in cats and dogs is not serious and symptoms usually subside in a month, but vets sometimes recommend hormonal supplementation or ovariohysterectomy (removal of ovaries and uterus) to prevent a recurrence.
[Photo courtesy of Nigel Swales via Flickr.]