What causes stubby tails?

[Bogertophis]

Well water eh? Pesticides can seep into well water and are known to cause birth defects.....

Pesticides aren't the only risk, all sorts of things can be an issue, stuff like heavy metals, nitrites/nitrates, etc. No telling the effects on snakes.

https://www.epa.gov/privatewells/pot...-their-impacts