Simplify the following text for a Grade 7 native English-speaking person.
Original: If one lioness gives birth to a litter of cubs a couple of months after another lioness , for instance , then the younger cubs , being much smaller than their older brethren , are usually dominated by larger cubs at mealtimesâ '' consequently , death by starvation is more common amongst the younger cubs .
Simplified: The cubs are very vulnerable when the lioness goes out to hunt and needs to leave the cubs behind .