There is at least one vet in Colorado who keeps seeing dogs for marijuana poisoning, and he thinks he knows why...
He doesn't think the dogs are getting into their owners stash, nor does he think they are being given the drug purposely. Instead, he believes the dogs have been eating human feces left behind by hikers and campers, and that there is enough THC in the poop that dogs are getting high.
The vet says he has seen 3-10 dogs a week suffering from this marijuana toxicity.
So, if you poop in the woods, take it out with you!!