The population can get sick and obese and not die because we are not in the wilderness apes and wolves don’t have that great of a time they die the moment they become even remotely unfit.

For most apes in captivity the life expectancy is nearly 50% greater than those in the wild even those who are in reservations, for some it’s duble or more.

You will not find gorillas older than 30-35 years in the wild those in captivity live up to 50-60.