Here's why:
* Gestation: The gestation period for a mountain lion is about 93 days.
* Raising cubs: Mountain lion mothers are very dedicated to raising their cubs. They stay with them for about two years, teaching them essential survival skills.
* Nursing and weaning: Cubs nurse for about 6 months and are weaned around 10-12 months old.
Therefore, it's usually around two years between litters, giving the mother time to recover from giving birth, raise her previous cubs, and prepare for a new litter.