Cheetahs give birth to their first litter at two years after a 3-month pregnancy. The cubs are kept in a lair for the first 2 months of their life, when their mother leaves them to hunt every morning, and returns at dusk. Cheetah cub mortality is high - out of 20 cheetah cubs born, only one will survive to independence. Cubs die mostly because they are killed by lions or hyaenas: their mother cannot defend them against these much larger predators. Cubs may also die from exposure or fire, or from abandonment if their mother is unable to find food. If they survive, the cubs will stay with their mother until they are 18 months old, after which they will roam with their littermates for another 6 months.