You have already received some good advice. But if you are renting or otherwise unable to add insulation, drywall, etc., there might be other options.
I live in South Dakota and have a room in my garage which is not insulated save for the ceiling (which really helps).
I simply stapled up some Reflectix foil/bubble insulation onto the walls, ceiling, and over the hollow-core door.
I then heat the 7'x7' room with an oil-filled, radiator-style space heater and it does a great job. I'm able to heat the room to 80* easily with the heater on its lowest setting - even though it's cold here now.
If you have a small area of the basement you could tape some of this insulation to the walls and then make a drape out of it to section off the areas without solid walls.
Or you could simply hang a bunch of it in a big circle and keep you snakes inside of that.
I do recommend one of these radiator style heaters over all other space heaters. I also recommend running it though a thermostat rated for 1500 watts minimum.
This picture shows my tiny snake room. We're moving soon so I could not justify insulating the wall cavities for one winter.

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Current snakes:
1.1 Gonyosoma oxycephala - (Silver/Yellow)
3.4 Gonyosoma oxycephala - (Green)
2.1 Gonyosoma janseni - (Black)