Rattlesnakes (and scorpions) are absolutely indigenous to Metro Phoenix, AZ. Whether they're on your property or not isn't the issue. The issue is that if you create a haven for them as you described - they will be happy to move in with you, sooner or later. Doesn't matter if you've never seen one there before. They live where (Phoenix, AZ.) you live.

Keeping your growth sparse and cut/trimmed close, discourages them from cribbing with you.

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