Setting
- We are in a European medieval society.
- Magic exists, but to answer this question you cannot use it.
About the creature
- This creature could be an "Edge of Tomorrow" kind of monster, with a central core that controls a bunch of smaller "soldiers" or something like a swarm of insects - a group of creatures that have the same shape and rank. The only restriction is that it must have a collective mind.
- The nature of the mind I'm talking about could be whatever you want: either they share thoughts or only feelings and rudimentary signals.
But if one unit of this race is in danger their fellow companions can understand it even if they are 1000 km away. - There are different groups and species of creatures with collective minds which differ in shape and habits.
- People can kill and analyze how many creatures they need.
Question
With that said, how would people be able to understand that these creatures have a hive-mind?