Just a guess because I'm not there to see it in person, but to me it looks like there's a moisture issue going on inside that block and they may be drain holes to allows water out.
The reason I say that is because of the black mold and whatever that coating is failing.
It would be interesting to see what's on the other side of that wall.
It this an above grade basement?

 

The holes are probably intentional as drain holes as Joe mentioned. Maybe stuffing some SS scrub pad material into then would keep the critter out.

The other side of the issue is where it got in as once in it has free movement through the blocks all around your foundation, blocks are usually not filled solid. So do your searching on the outside and that is where you can seal all holes for both the snake and the water.

Water can be entering below grade but I suspect the snake entered at grade somewhere. Being small means a small hole and also means probably more than one.

Good luck

Bud

 

Thank you for the input! This is a below grade basement. The other side of this wall is the backyard so I cannot get to the other side.

 

Great idea on the scrub pad for blocking, I will be sure to do that!

Thanks again on the tip about checking things out at ground level. I am doing to do a detailed search and caulk things up a bit. I ended up catching the snake with some strips of duct tape on the ground sticky side up. I was able to cut away the tape and let the little guy go in the woods down the street. Live and let live.

 

Good deal on letting the non-poisonous snake go...I have copperheads all over the place so that's a much bigger threat.

I used some steel wood brillo-pads to plug some holes and the mice ate thru it...I then went with stainless steel fine mesh and that ended it...

Since you have a basement, you surely have to be N of Texas so your snake issues will soon cease w cooler temps...