The concerns about pine are a fairly recent development. You don't have to go far back in the forum archives to see it commonly recommended as a substrate. Keep in mind that most of the colubrids bred for the breeder and pet trade market have been produced on pine shavings. I'd gather until recently all of the rodents fed to these snakes were produced on pine.
This does not necessarily make it right, but it certainly suggests acute toxic effects are not common.
And speaking of shavings, that's where the use of pine creates the biggest concern since that increases the relative surface area of the toxic phenols exposed to air. Solid pine is not as big of a deal. But generally we assume it's always going to be sealed when used for caging.
I don't recommend unsealed wood of any type but I have seen an awful lot of unsealed pine in cages over the years. I think it would be okay for a temporary setup but I would not stretch this out too long. At least cover the underside of each shelf (the part the snake is exposed to) with some contact paper for lining kitchen shelves, etc. Note that it does not always stick to pine very well.
Also, racks made from solid pine are more likely to shrink and expand or even warp slightly with changes in environmental conditions. For this reason I don't recommend solid pine for rack systems where pretty tight tolerances are required.
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Current snakes:
0.2 Gonyosoma oxycephala - (Silver/Yellow)
3.3 Gonyosoma oxycephala - (Green)
2.1 Gonyosoma janseni - (Black)
3.3 Gonyosoma janseni - (Black & Tan)
