I was thinking about the “mama grizzly” model of womanhood and decided to do a little research, since this, according to Ms. Palin, is the way of America’s future. It turns out the Mama Grizzly’s excellence as a mother—the reason Sarah Palin chose her as her symbol—is a direct function of her ability to become a mother when circumstances are precisely right and not before. In a nutshell, Mama Grizzlies abort.
What I found: Not only do female grizzlies like to play the field—with multiple partners and repeated encounters that last up to an hour—they also terminate the pregnancy if the timing is poor. A female grizzly won’t carry a fetus to term unless she is in “peak condition” and has the wherewithal to support her offspring. As is the case with other bears, “if the mother has not accumulated enough fat to sustain herself as well as developing cubs,” the fertilized embryo will be reabsorbed into the not-going-to-be-a-mother-yet’s body.
After mating, the female may be pregnant, but that does not mean she will give birth to cubs. There is an old joke that you can’t be half pregnant, but bears have proven this statement to be false. Bears, weasels and some seals have developed a process called delayed implantation. The fertilized egg develops into a small embryo called a blastocyst. This is where the interesting stuff begins. After this brief period of development, the fertilized egg suddenly stops growing and simply floats freely in the uterus for several months.
If a sow is in peak condition when she heads into her winter den, the embryo implants in the uterus and begin to develop. She’ll wake up during January or February to give birth. …
If the sow is not in peak condition at the onset of hibernation, her body will reabsorb the embryo and not give birth that year. This gives bears more control over their reproductive rate than just about any other animal.
Cross-posted from Millicent and Carla Fran.