I spent three evenings reading everything I could find. Not pest control websites. Actual wildlife biology.
And I found something that should have been obvious but never was.
Snakes don't navigate the way we think they do.
They don't primarily use smell or sight to choose where to shelter.
They use vibration.
Their entire nervous system is tuned to ground movement. It's how they detect predators. How they assess safety. How they decide whether a location is worth settling in.
A quiet patch of earth near a structure a garden bed, a shed wall, a compost corner reads to a snake's system as: SAFE. STILL. SHELTER HERE.
Every spray I used. Every granule. Every $320 perimeter treatment.
They all worked on the surface. Not one of them touched the underground environment where snakes actually make their decisions.
That was the piece I'd been missing for two years.
Not what repels snakes from the air.
What makes the ground itself somewhere they won't go.