Beasts Icons

Maby i missed it somewhere but i need to ask.
I saw yellow and red beast with big yellow icons over their head but not all of them have one.
I really want to know why. I dont mean in the mini map ofc. I mean over the beasts when you saw them.
If all beasts have this yellow mark over their head its hard to kill it by mistake.
If iam missing something here i will be glad to know.
Thanks

Maybe because the yellow icon beasts are useful for the recipes to beast craft. While you can capture a lot of beasts without icons, those ones are needed to have recipes used. The red icon beasts are mostly with a new beast craft recipe.