Pacman Frog Pupil Constriction and Dilation

[ceratophyrys]

So I just got a mint green pacman frog about a month old and I've noticed that when there is food near him, his eyes will look all black (dilated) but when he burrows himself in the substrate his pupils will constrict. I've read that when they sleep they close their eyes, is it possible that mine constricts its pupils when asleep??