Are the cave insectoids supposed to starve immediatly?

The megaspiders and spelopedes have no clue how to feed themselves though it seems.

They started getting malnourished and roaming out of their caves until they hit my little makeshift base.

So many conflicting statements.

Started getting malnourished, so they don't start out starved. No idea how to feed themselves, but they also attack you, because you are a food source...so they do know how to feed themselves.

Are they supposed to just give up on the life they have presumably been living for thousands of years and charge you from across the map?

Pressumably: is just that, assumption. If that doesn't work, game mechanics > logic. And yea, your survivors will eat anything as well when they're hungry. So charging across the map doesn't seem that far stretched.