Despite promising initial signs and after months of monitoring, Er Shun, the female giant panda currently in residence at the Toronto Zoo, is not pregnant.
The panda was artificially inseminated in late April and over the past few months has demonstrated signs of pregnancy through urine and hormone tests, ultrasound examinations and behavioural observations. But zoo officials have confirmed that she was experiencing a pseudopregnancy.
Pseudopregnancies, in which the animal exhibits symptoms of pregnancy but is not actually producing an offspring, are not uncommon in carnivores such as dogs and cats, including larger variants like lions and tigers.
When a pseudopregnancy occurs, the animal responds as if an offspring were present, even going so far as to engage in behavioural changes like nesting. Much is still unknown about these cases, particularly in giant pandas, due to their very delicate breeding periods, which make collecting data difficult.
“In a lot of these species with pseudopregnancies, we don’t really understand what’s going on, but the body just kind of takes over whether there’s a live fetus or not,” said Dr. Gaby Mastromonaco, the zoo’s curator of reproductive programs and research.
“It’s more particular to pandas, and we can’t even understand yet — is that evolutionary, is it because of what they eat, seasonality? It’s just really tricky to try to tease out why it’s happening, and why it tends to be a much higher rate in pandas.”
There are no definitive pregnancy tests for giant pandas, which have very delicate breeding periods. A female giant panda has only one reproductive cycle per year, for a period of 24 to 72 hours.
The next step for the staff will be monitoring Er Shun for signs of this next reproductive cycle. Zoo officials remain hopeful that they will be able to bring both pandas together in 2015.