How do you analyze her hormones?
To analyze Billie Jean’s hormones, we are collecting both urine and fecal samples. We send our samples to the endocrine lab in the hope that this data will give us details about when Billie Jean’s hormones spike and diminish. By looking at both, we can determine which gives us a better signal.
This information could also alert us to more subtle clues to her estrus cycle that we may have been missing. For example, it has been a common thought that female Andean bears go into estrus once seasonally. However we are seeing from Billie Jean’s behavior that this may not be exactly right.
It may also help inform our decisions on how long bears remain in the same space.
What have you learned by studying her hormones thus far?
In 2016, Billie Jean was observed breeding with Cisco, the father of her previous cubs. She displayed behavioral clues that she may have been pregnant, such as spending more time in her den, and she gained weight. However, until we had conclusive evidence of the presence of cubs—such as an ultrasound or a cub birth—we really didn’t know if her behavior was indicative of a true pregnancy.
Through endocrine research that studied the hormones of giant pandas, we learned that some bears can experience pseudopregnancies—or false pregnancies. In a pseudopregnancy, the bear’s behavior and hormones look the same as if the female were pregnant, but she is not.
Because Andean bears experience delayed implantation (also known as embryonic diapause), we do not know exactly when a fertilized egg (blastocyst) attaches to the uterine wall. Females are not pregnant until the blastocyst implants. Nobody knows what the trigger is that dictates when this happens. What we do know is that it can take as long as six to eight months.
The possibility of pseudopregnancy, coupled with embryonic diapause, makes bear pregnancies nearly impossible to confirm. Despite all behavioral indications that Billie Jean was pregnant in 2016, unfortunately, no cubs were born. Her hormones from this period show elevated progesterone concentrations that stay elevated for roughly 60 days—the typical length of a bear gestation. Because no cubs were born, this could indicate that Andean bears, like giant pandas, experience pseudopregnancies. It is also possible that Billie Jean experienced a miscarriage, or may have resorbed the growing embryos.
We hope to compare the data gathered from her 2016 hormone profile to a pregnancy that results in cubs. We will be closely monitoring Billie Jean throughout the summer and fall. Our hope is that she will have cubs later this year.