Thanks for the nice comments, guys. We had fun performing this study and the dogs thought it was a great game.
"I am a little surprised though that neither seems to have much useful effect."
@Ben- We only looked at whether the odor-proof bags performed better than ziplocs. We did not address the question of whether either had a useful effect at all. Here is an abstract suggesting that ziplocs may decrease bears ability to smell food, though one has to wonder whether the difference between 6 and 9 seconds is significant in a practical sense.
Wilderness & Environmental Medicine
Volume 21, Issue 4 , Pages 375-376, December 2010
Ziploc Bags for Preventing Bears from Smelling Food
Background.—Wilderness activities occasionally result in
bear-encounters. To deter bears from detecting food scents, the
American Bear Association recommends double-bagging food
carried into the wilderness.
Objective.—Our objective was to determine if food sealed
in double-bagged Ziploc bags would decrease the ability of
bears to detect food scents as compared to food in unsealed
Methods.—This was a prospective randomized singleblinded
study performed on bears at Northwest Trek Wildlife
Park, WA. Two black bears (Ursus americanus) and 2 brown
bears (Ursus arctos) were presented with open buckets in front
of their enclosures: one concealing food wrapped in 2 layers of
Ziploc bags and another with empty Ziploc bags. The time the
bears spent at each bucket was recorded for 30 seconds. In the
first phase, Ziplocs were open; in the second, Ziplocs were
Results.—The average time the bears spent at the open
Ziplocs with food and open Ziplocs without during the first
phase of the experiment was 9.573 and 6.613 seconds, respectively
(N _ 75). The average time spent at the closed Ziplocs
with food and closed Ziplocs without in the second phase of the
experiment was 6.25 and 6.8875 seconds, respectively (N _
80). The standard deviation for all average times was 1.5
seconds. An independent samples 2-tailed t-Test demonstrated
a statistically significant difference (P _ 0.032) when compar-ing
the time the bears spent at the open Ziplocs with food to the
closed Ziplocs with food. There was no statistically significant
difference between the controls from both phases of the experiment
(P _ 0.854).
Conclusions.—The bears spent a statistically significant
greater time at the open Ziplocs with food compared to the
closed Ziplocs with food. These data suggest that sealing food
in 2 layers of Ziploc bag may decrease the ability of bears to
detect the scent of food from within. We advise following the
Clark M. Rosenberry, MD
David C. Hile, MD
Troy H. Patience, BS
Fort Lewis, WA, USA
Richard L. Sartor, MS
Angela K. Gibson, MS
Northwest Trek Wildlife Park, WA, USA
@Tony- I can answer your question about foodsaver bags, though not with a direct comparison. I had relied on the police officers to provide the "scent packets" for the study. Naively, I only questioned type and weight of the product, but not how they were packaged. After the study, I theorized that the seal must be the weak link in these bags and proposed a second study where we would investigate bags that were heat sealed to remove the opening. The officers laughed and told me the dogs would find them anyway. As it turned out, the drugs we used were sealed in foodsaver bags and then wrapped in a heavy canvas outer covering to protect the dogs from accidental exposure. I don't pretend to understand the intricacies of olfaction, but I developed a tremendous amount of respect for the dogs over the course of this study. Scent will find a way.