Do sensors scare off the AI?

I'm just curious.... i have been under heavy attack by the Kryn,,,

My fleets are more powerful than theirs, but i have few, not enough to defend all my area.... The Kryn seemed to have an uncanny ability to sneak fleets in wherever i am week and start destroying my starbases until my fleet catches up and destroys them.

So i responded by sending out sensor ships along my boarder.

The Kryn pretty much stopped attacking entirely?

So if they are not able to sneak in, they give up?? Just wondering?