It just depends where you are at. We've found 5 pythons in one night. You just have to look in the right places. Monitors are all over Key Biscayne as well.
As far as the track goes, it looks too linear to be a gator, but I'm not sure. Is there alot of dirt pushed up on the sides like something heavy was there? Maybe some thrown up on a left side or right side. If not, and the vegetation looks like it has been trafficked, it might just be a well used rat or mammal run, that took a turn for the worse on a muddy night.
That hole, if near the water, has got to be a crab hole, probably of a ghost crab. Check it out at night with a spotlight, hold it by your head and do sweeps of the area, whistle or make a noise so that you can get any mammals to look at you. You'll be able to see the eyeshines. If you are wondering about gators, take the light out there at night and scan the water, you'll get their eyes shining back as well.