The Ursack TKO was evaluated for
adequacy to provide bear-resistant food storage and to assess potential
resource effects associated with securing the Ursacks to trees. The Ursacks
were tested using three different configurations (Ursack only, Ursack
with Ursack vapor barrier, Ursack with aluminum insert) and three different
backpacking cuisines to represent a range from very basic (dry food only)
to two increasing levels of diversity that added snacks, liquid and finally
some fresh produce. The baited bags were hung overnight or longer in areas
with known bear problems, and the results were recorded and photo-documented.
Three Ursacks were randomly selected from these test units (excluding
those used with aluminum inserts) to test for cumulative damage by exposing
them to a minimum of three more bear encounters. Three new units were
used by the Inyo National Forest staff to test options for using the Ursack
above treeline. One new bag was dedicated to testing the ability of the
Ursack to resist marmot damage, and another was fitted with a transmitter
to see how far bears might carry the bag if it was not secured properly.
Bear staff were contacted in eight parks to learn of their requirements
and experiences regarding the Ursack.
All of the Ursack TKO tested remained
intact during the testing. The primary damage was small
micropunctures from the canines causing thread separation. Additional
damage included some seams losing one layer of thread, pulled and lose
threads, partial failure of grommets, abrasion, and formation of fuzz
from tiny broken fibers. The bags continued to remain intact even after
the cumulative damage testing though the density of micropunctures did
increase and the bags did lose 0.7 to 1.9 % of their weight. The vapor
barriers were punctured and some were severely damaged. Aluminum inserts
became tightly wrapped around the food and some inserts were punctured.
One was ripped into smaller pieces. Marmots were not able to penetrate
the Ursack, but some small animal (believed to be a mouse) did chew a
hole through the Ursack twice.
Food loss from the bags was evaluated
by weighing the Ursacks and their contents before and after each test.
Weight changed from a gain of 2.9% due to acquired dirt and absorbed moisture
to a loss of 7.3% primarily from punctured containers of liquids. There
were no significant differences in the weight change among the different
configurations (bag vs bag and vapor barrier vs bag and aluminum insert),
but significant differences in weight change did exist among the different
cuisines (basic vs intermediate vs diverse). This was attributed to those
Ursacks that contained fluids. Overall, loss of solid food appeared to
Most of the food in the bags was mutilated, and it acquired a foul smell.
The aluminum inserts did improve the amount of food that survived intact,
but the insert also created a safety hazard where it was punctured or
ripped apart creating sharp edges or small pieces of sharp metal mixed
in the mutilated food.
Most (89%) of the Ursacks could
be untied from the trees at the end of the tests without using tools.
Untying the bags that did not require tools took 23 to 161 sec., and up
to 6 min. were needed to untie bags that eventually required a tool to
loosen the knots.
Bears carried inadequately-secured
Ursacks short distances suggesting that users should be able to locate
most bags that might get carried off by bears. Distances carried during
the four tests were 0.3m, 1.6 m, 5.8 m, and somewhere between 41 and 67
The testing in rocky areas indicated
that it was feasible to secure the Ursack in areas above timberline. However,
the user will need to carry extra gear for that to be successful.
The bears efforts to break into the Ursacks generally caused some damage
to the tree bark and to the soil. More damage was sustained by trees with
a soft bark than those with a hard bark. However, some level of bark damage
was found on every species (6 species) of tree involved in the testing.
Eighty-five percent of the trees showed some bark damage on their first
use as a mount for the Ursack. Some of the trees that were reused did
appear to experience cumulative bark damage. Ninety-two percent of the
test sites showed damage to the substrate at the test trees. This included
removal of the litter and small vegetation leaving bare soil with a tilled
appearance. The damage usually did not go all of the way around the tree
but it extended outward 69 to 181 cm from the tree trunk.
Because of the stiffness in the
fabric and force required to open and close the Ursack, an anticipated
misuse of the Ursack might be people leaving it open around camp to facilitate
getting snacks. Other errors might include leaving the Ursack unsecured
when trees are not present, failing to tie an overhand knot by the cord
lock if the bag is not snug to the tree, or failing to tie a figure eight
knot to secure the Ursack to a tree.
Of the eight parks contacted, three
permit (but not encourage) use of the Ursack for food storage. One park
allows the Ursack to be used above 7,000 ft only, and four parks require
use of foodstorage facilities provided. Some of those parks permit canisters.
As a bear-resistant bag, the Ursack
TKO performed well. The testing relieved concerns about ability of the
Ursack to remain intact and retain solid foods, even with multiple bear
encounters, concerns about users being unable to untie the bag, concerns
about the bag being carried off to become longterm wilderness trash, and
concerns about being able to secure the bag where trees are absent. However,
some resource and safety issues remain. The testing reenforced concerns
about bark and soil damage, and the analysis generated concerns about
safety and about the possibility of users dumping mutilated food in the
wilderness rather than eat it or carry it out to a proper disposal facility.
The safety issues include: 1) the bears efforts creating small sharp metal
or plastic objects inside the Ursack that could get mixed into the food,
2) the chance of a user being injured when attempting to chase a bear
from their Ursack to prevent their food from being mutilated, and 3) the
remote possibility of rabies being transferred via saliva in a bag. It
might be possible to mitigate these concerns with appropriate warnings
and use restrictions.