I let my BP out in the front yard on occasion as well. I'd personally never take it off my personal property for fear of all the bad things that can happen - especially if there are laws to the contrary. You've always got your idiots that will cause a stink about it. Besides, I think my yard is safer because I know when/if we've sprayed, etc.
Anyway, I was wondering the same thing the other day. My take on it is this: I believe that all animals benefit from some type of enrichment. I think that the new, more natural environment of the outdoors helps to stimulate their senses and provides them with some type of enrichment that is beneficial to their well-being and mental state. That is as long as my BP feels secure - not out in the open where he's vulnerable and no place to hide....I like to put him in the grass that's a bit taller so he at least has some cover. No, I can't prove my thinking is correct, but animal enrichment is practiced on many species of animals and I can't imagine it not being good for my snakes either.
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Check Out My Albums
1.0 Ball Python "Aragorn"
1.0 Kenyan Sand Boa "Gimli"
1.0 Saharan Sand Boa "Frodo"
0.1 Rough-Scale Sand Boa "Arwen"
0.1 California Kingsnake "Gentoo"
1.0 Mexican Black Kingsnake "Indigo"
1.0 Snow Corn snake
0.1 Australian Cattle Dog/Pointer
"Kira"