How does Baby Groot know Drax is looking at him when he dances?

Baby Groot stops dancing whenever Drax looks at him, we see this almost instantly at the end of Guardians of the Galaxy and also in the opening scene in Guardians of the Galaxy Vol. 2. Why he stops dancing is pretty obvious, Drax disapproves of such things and so he doesn’t want to get hurt by him. Gunn has also said pretty much the same thing in an interview:

“There was actually a scene that we cut from the movie where big Groot was dancing to ‘Livin’ Thing’ by ELO,” said Gunn. “And it wasn’t such an elaborate dance. It was more that he was just moving up and down like this, and Drax was dismissive and gave him this look like he was a loser when he did that.”

Gunn added, “Dancing is ludicrous to Drax. I don’t think he understands it. If Drax owned a town, if he was a mayor, the first law would be no dancing. But yeah, so at the end of the movie, little baby Groot didn’t want to get caught dancing, because he would kill him.”

_{comicbook, Guardians Of The Galaxy Cut Scene Reveals Why Baby Groot Hid His Dancing From Drax}

So, we know why he stops dancing but do we know how he even knows Drax is looking at him in the first place so he can stop? In the GotG2 opening scene he might have heard it was Drax behind him, however, he doesn’t stop dancing straight away only when Drax looks. And when you watch it at 0.25 speed Groot isn’t even looking towards Drax.

How does he know Drax is looking at him when he can’t see behind himself?