Ursack Update

November 09, 2004
November 8, 2004.

The Sierra Interagency Black Bear Group (SIBBG) conducted an exhaustive wilderness study of 15 Ursack TKOs in the summer of 2004. Despite numerous bear encounters, no bears or marmots were able to access food from an Ursack. SIBBG, through wildlife ecologist Harold Werner, produced a 20 page single spaced footnoted report accompanied by hundreds of photographs and field notes. The abstract from that report is reproduced below. In spite of Ursack's success in keeping bears from getting food, SIBBG refused to grant conditional approval for its use--primarily on the basis that there could be damage to trees and soil. Ursack has not yet determined how to respond.

Although Ursack is grateful for SIBBG's considerable effort in testing the TKO, the report must be read with the knowledge that SIBBG did not deploy the TKO in the same manner that campers are advised to: (1) SIBBG did not use the odor bag to mask odors--in fact the outside of the TKOs were smeared with bait in order to entice bears; and (2) SIBBG did not suspend the TKOs from tree branches, but instead tied the bags around tree trunks. This enabled bears to pull the TKOs to the ground where they could be easily stomped on and chewed. Ursack does not fault SIBBG for these testing techniques because they were trying to determine whether bears could chew through the TKOs. Had they masked odors or tied the TKOs to branches, the bears might never have attempted to gain access. IF ODOR BAGS HAD BEEN USED AS DIRECTED AND THE TKOs HAD BEEN TIED TO TREE BRANCHES (NOT TRUNKS), IT IS LIKELY THAT THERE WOULD HAVE BEEN CONSIDERABLY LESS DAMAGE TO THE FOOD CONTENTS. PLEASE KEEP THIS IN MIND AS YOU READ THE ABSTRACT.

ASSESSMENT OF MODIFIED URSACK TKO on behalf of SIBBG dated September 28, 2004


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 be insignificant.
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 m.

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.