@Diane
” The other issue is proximity–do the bags reduce wind-borne odors bringing a hungry bear to your camp?” ”
They will certainly reduce the odors by some amount. The question is by how much. It is a near certainty the nylofume works far better than a Ziploc bag, because even I can smell odors through a Ziploc bag, but not a nylofume one.
“Once the bear is there, it may not work, but as a bear is searching for food, will it be attracted?”
That is the crux of the issue, and one that has not been completely resolved, IMO, certainly not by a test under very artificial conditions with dogs trained to detect drugs. Too many issues left unaddressed. See below.
” If you are camping in impacted areas where bears know that people and food may be, it’s worth it to stroll by and check it out. Then, the OP sack won’t deter them, unless just plastic alone slows the transmission of the odor.”
While I would never sleep with my food in such areas, precisely because they will come even if they can’t smell food, I question your statement about the OP sack not blocking odors, at least effectively enough not to attract a bear from a distance. That remains an unanswered question, IMO. In any case, I consider habituated bear country to be either canister country or in forested areas where I know I can execute a good hang, hanging country. This excludes most of the PNW, BTW. Down sloping tree branches make for very poor hangs.
” I’m pretty sure it doesn’t: I bet a high proportion of campers have some or all of their food sealed in ziploc bags these days.”
If you are talking about Ziploc bags alone, you are on solid ground, IMO. If you extrapolate from that to nylofume bags, I think you are on much shakier ground. Those bags are used to protect food and other household items in situ during fumigation of houses for pests, and are guaranteed to be odor proof. The question for me is are they 100% odor proof when bears are in the picture, or is the manufacturer using a different standard of “odor proofness”? I am not sure that they would be if a bear’s nose was in close proximity to a nylofume bag containing food. I am, however, confident that they block odor effectively enough to avoid attracting a bear passing, say 200 meters from my camp, in areas where bears are not habituated or highly unlikely to be present, and I can’t do a proper hang. Confident enough to sleep with my food.
” Testing under field conditions isn’t really science, and isn’t ethical:”
Let’s deal with the ethical issue first. For the purposes of the topic under discussion, I think we could all agree that dogs trained to detect food would be an adequate substitute for using bears. If they could detect the food, then bears, with their far more sensitive olfactory sense would also be able to detect the food.
” too many variables (how do you know that a bear would have happened by to investigate your food? Failure of sack=rewarded habituated bear=dead bear). I figure one would need to test smelly food, neutral food like oatmeal or crackers, and a bag with a non-food/attractive product, to see whether they investigate without an odor cue.”
For a more realistic result, conduct the test in an area with a known bear population, use motion detecting cameras to determine if they were drawn to the tent containing the bagged food, and drive them off when they got within, say, 5 feet of the tent with flash bangs of some sort, or perhaps an electrified perimeter. No harm done to the animals, and no reward. Such tests could be done with both OP sacks and nylofume bags, and I would want a double nylofume bag inside a waterproof roll top bag to validate, or not, my own approach. I would also want the test conducted with foods of varying odor intensity, to replicate the range of foods carried by backpackers. If we wanted to make the tests even more realistic, they should include cooking versus no cook scenarios, simply because a cooking scenario would provide the dispersed odors that would likely bring a bear in close to investigate, something the no cook approach is intended to avoid. I realize we cannot reduce this kind of an experiment to one variable at a time, but I do believe it would produce useful results. Close enough for gummint work, as the saying goes. I think what I have described here, while not entirely controllable, in the strictest scientific sense, would give us a lot of useful answers as to what works and what doesn’t, even if dogs were used.