Could the oil I'm seeing around that bolt be residue from winterizing? I tightened the bolt a half turn, and also cleaned around the bolt. No additional oil has leaked.
The problem is your sig says a Alpha and the oil fitting is on the Alpha GEN II drive. We need more pics to determine the type. do the hyd rams bolt on or slip on?
There is no winterizing process involving an oil leak in that location. The GEN II has a O ring seal in that area, the standard Alpha does not.
My advice is to do a bit of degreasing/cleaning in the area and see if the oil comes back (or not).. If not, then it may have just been the loose bolt . . . if not, then best to look at the o-ring.