I had an interesting experience with a sniffer dog coming back from an international trip. Waiting for my luggage we watched a lady with a beagle wander around for quite a while checking out bags. After quite a while the dog got to my carry-on bag and took an interest. The Agriculture Agent looked inside and found the peel from the banana I'd finished over eight hours ago in the departure lounge just before boarding. I had gotten rushed and wrapped it in a napkin when I didn't see a trash can handy and had forgotten all about it. That peel wouldn't have lasted an hour in my office trash can but its smell was completely overwhelmed by the complex bouquet from a planeload of tourists in coach.

The sniffer dogs are impressive but they generally are allowed to get pretty close. I didn't get the sense that the dog who busted me smelled that banana before it got right up on it. Maybe it did and was just very disciplined but since people were heading out as soon as their bags arrived I'd think that if it had sensed something from a distance the procedure would have involved a more direct interception.

They say that a bear's smell is much better than a dog's and the background environment in the wild is probably much less complicated than what a compliance animal deals with but there's still got to be a finite detection range that is dependent on barrier effectiveness.

Since their noses probably evolved to detect animals rather than sealed ramen noodle packages I suspect that any bear from a wide area can detect a sleeping hiker from a long way away. That suggests that an active campsite will probably get Cheech-and-Chong-at-the-border level scrutiny and no amount of wrapping should probably considered reliable. I wonder, though, just how far a soda bottle full of peanuts and oatmeal would have to be from a bear's path to be detected without the hiker's presence as a clue. Tens of feet? Hundreds? Are they also cuing on something else, such as an unnaturally-shaped canister or a bag dangling in the breeze to arouse curiosity and intense sniffing? It's too bad there's not a reliable measurement system but if there were I guess the border folks would use that instead of dogs.