by Barbara Walvoord
(From Lathrop Lamp Post, Jan. 26, 2017)
Our black bears are mostly sleeping away the winter in their dens, but mama does wake up in January or February for one important event–giving birth. She’ll have 1-4 cubs, though 2 are most common.
The newborns, less than a pound, are blind and hairless. Mama stays sufficiently awake to avoid lying on them and make it easy for them to nurse. Her milk must get them up to 4-6 pounds by spring. Nursing, with no food for herself, she may lose up to 1/3 of her body weight, while non-nursing bears lose only 15-25%.
The happy birth began seven months ago, when mama mated repeatedly over several weeks with one (or several) guys, who then went on their merry way.
There’s an old joke that you can’t be half pregnant, but in fact she was. Her fertilized egg developed into a small embryo that then stopped growing and floated free in the uterus, waiting. If mama was fat and healthy when she began hibernation, then the embryo attached to her uterus and grew. If mama was too skinny, the embryo was absorbed back into her body.
Despite her size and those long claws, useful mostly for climbing, mama is too slow to pursue prey animals. Her stocky body is for storing fat and surviving the winter. So she feeds that stocky body–and those hungry cubs–with many, many small morsels: tender new plants in spring, and then the real fat and protein stuff: berries, nuts, and insect larvae.
But 90% of insect larvae eat only native plants. So we nurture our bears when we remove invasive plants that crowd out natives, and when we reduce the pesticides that kill insects, so our mama bears can go fat and healthy into their dens and get all the way pregnant.