Here's why:
* Gestation: Black bears have a long gestation period of approximately 6-8 months.
* Delayed implantation: The fertilized egg doesn't immediately implant in the uterus. It can stay dormant for several months before implantation occurs.
* Hibernation: Females often give birth during their winter hibernation period. This allows the cubs to be born in a safe and protected environment.
* Nursing and care: Mother bears nurse and care for their cubs for about 18 months. This intensive period of care limits the frequency of reproduction.
However, there are variations based on factors like:
* Age: Younger bears tend to reproduce less frequently than older, more experienced mothers.
* Food availability: Abundance of food can influence a bear's reproductive cycle.
* Individual health: Overall health and nutritional status play a role.
So while the general rule is every other year, there can be exceptions depending on the specific circumstances.