The way i tell if its a big bodied buck is if i can lay a 30 06 bullet in the widest part of the track width wise and the bullet fits in it then i know its a big buck.
Don't pass on the first day if you would shot it the last day
I'm with thunder on his theory...I lay a .270 cartridge in the width of the track and if it fits I'm on him like a coyote...that's the way I love to hunt Mule Deer(got it from my Grandfather) he loved tracking. Another good indication is in light snow a big ole buck will walk lazy by dragging his feet unlike a big doe which will pick up her feet most of the time..
As in the first pic the buck was running and they'll will tend to be bigger especially in soft ground..follow the track until he stops running and see what it looks like..The buck I got this year had a nice foot on him and I tracked him down to his bed..He field-dressed 217 lbs.