Hm well:
1) Walk up to them and then when you hear their "!" noise, start running. They'll detect you faster if you just run at them.
2) Chase them toward the center of the map. They'll escape out of bounds if they can and you can't follow them.
3) Try and remember what obstacles will be in your way in the *next* map square you chase them into.
4) Don't give up if you hit a tree but if they have a big lead on you, let them go and try again when they settle down.
5) Try chasing them diagonally? For... math... reasons you move faster diagonally.