Study on Bear Spray Confirms Performance Limitations

 Image of grizzly bear  by Troy Nemitz, used with permission.

An Investigation of Factors Influencing Bear Spray Performance" was published on 1 October 2020 in the Journal of Wildlife Management. The lead investigator was Tom Smith, of Brigham Young University.

Tom Smith is well known for his publications on bear spray and firearms effectiveness when dealing with bears.

Tom Smith graciously supplied me with a copy of the full paper, which shows all the results of the study. The study provides useful information, which can help in choosing between bear spray and other systems, such as firearms, as well as in understanding some of the limitations of bear spray under different conditions.

The first sentence in the paper advances a dubious premise: 

"We can contribute to bear conservation by reducing bear mortalities due to human-bear conflicts. " 

It is an interesting premise. It is not obvious, self evident, or indisputable. 

Bear populations must be managed to be conserved. The most effective management tool to keep bears from overpopulating is to harvest the surplus population.  

Brown bear, polar bear and black bear populations are increasing in most places where they exist in North America and the Arctic. They are not endangered. As the populations increase, there are conflicts with humans. 

At any given time, the numbers of bears which need to be harvested will vary. Bears involved in bear-human conflict are a very small, but increasing number. The number required to be harvested to keep a stable population is, in nearly all situations, much higher than the number of bears involved in bear-human conflicts.

Reducing bear mortalities in human-bear conflicts means more bears will need to be harvested in regulated hunting seasons. 

It is preferable that problem bears be selectively harvested. This is done automatically when human-bear conflict is resolved by harvesting the bear. A bear killed in a human-bear conflict, is one less bear which needs to be harvested in a regulated bear hunting season. It is one less bear with a propensity to come into conflict with humans.

Reducing bear mortalities due to human-bear conflicts only shifts which bears are harvested, not the number which need to be harvested to keep bear populations stable. 

There are numerous safeguards in place to guard against the indiscriminate harvesting of bears, which might be disguised as a legitimate response to a human-bear conflict. 

Reducing bear mortalities in human-bear conflicts does not appear to be a valid reason to use bear spray compared to firearms, to improve bear conservation.

There are valid reasons for people to use bear spray instead of firearms to protect themselves and their property during human-bear conflicts. Here are two:

• places where firearms are not allowed due to legal prohibitions
  
• people who, for various reasons, are unable or unwilling to use firearms effectively or responsibly

The reasons for studying the effectiveness of bear spray under varying conditions are summarized in the abstract of the paper. From wildlife.onlinelibray.wiley.com: 

Several studies have documented the effectiveness of bear spray in protecting users from aggressive bears. Bear spray failures, however, have also been reported along with speculation regarding the influences of temperature, wind, repeated canister use, and canister age on spray efficacy. We designed lab and field experiments to document the influence that temperature, wind, repeated discharges from the same canister, and canister age have on bear spray performance.

The recommendations from the paper are given at the end of the abstract: 

We recommend not test‐firing cans, keeping cans warm when in the cold, and retiring them when ≥4 years of age. Our results provide no compelling reason to not carry bear spray in all areas where bears occur, even if it is windy or cold.

All experiments are limited by time and cost constraints. They may provide useful information, but it is important to understand the limitations of the experimental design. 

The experimental design of the study measured and simulated the physical dispensing of the spray. It did not measure the effect of the spray on bears in various conditions.

The dispensing of the spray under various wind conditions was simulated in a computer program, using data obtained from high speed video of the spray plume in calm conditions. It was not measured in various natural wind environments.

The effect of various temperatures on bear spray performance was obtained by chilling the bear spray canisters, not in exposing the spray to environmental conditions, and dispensing the spray in the environment. Bear spray may dispense somewhat differently in air that is the same temperature as the bear spray compared to cold bear spray dispensed in warmer air. 

There was no consideration of synergistic effects. The natural environment is not the same as laboratory conditions, nor can it easily be simulated in computer programs. Natural effects often combine and reinforce each other in unexpected ways. I observed this during 30 years of testing in natural conditions during my career in Army Research, Development, Testing and Evaluation. 

There was no consideration of precipitation or foliage or other obstacles, or of potential physiological variations in bears at various temperatures, for example. 

We can speculate on what effect a combination of cold temperature, wind, rain and foliage might have on a plume of bear spray, but it is difficult to measure.

Given the constraints of the experimental design (all experimental designs have constraints), the results obtained are interesting and sobering.

The most pronounced effects were from wind. All winds over a very low threshold ( 1 m/sec ~ 2 mph, a barely perceptible breeze) had a profound effect on the range of the bear spray. Winds moving in the direction of the spray extended its range to a full 10 meters (33 ft) and beyond. All head winds over 1 m/s  limited the range to 1.5-2.3  meters (5-7 ft) (as seen on Figure 9). All side winds over 1 m/s limited the range to 2.5-3.5 meters (8-11 ft) (Figure 9). The figure is not reproduced here due to copyright restraints.

Cold temperatures had the next most significant effect on spray performance.  When the temperature was below 18 degrees C, (64 degrees F), the spray plume, in calm conditions, extended a bit over 4 meters (13 ft). At temperatures below -17 degrees C ( 1 degree F) the plume was considerably narrowed. Below -23 degrees C (- 9 decrees F), the plume was very narrow. The range of the plume was about the same, a bit over 4 meters in calm air.

From the deposition of the spray on paper on the ground, in images published in the paper, it appears the plume was about 14 to 12 inches wide at the lower two temperatures.

Age of bear spray canisters did not have an extreme effect. There was a slow, gradual, loss of propellant over years.  It appeared most bear spray would be effective for at least a decade.

The pressure at the nozzle dropped very rapidly as the bear spray was dispensed. An initial 1 second spray reduced the pressure by about 1/2, and uses about 1/2 of the spray in the can. Subsequent sprays release much less product. 

The results of the tests explain the lukewarm recommendation:

Our results provide no compelling reason to not carry bear spray in all areas where bears occur, even if it is windy or cold.

From the results of the study, readers might draw this conclusion: 

The results show compelling reasons to favor firearms over bear spray in conditions where there may be wind or cold. The reasons are clear.

- Firearms work reliably and well in cold and wind. Both handguns and long guns consistently have effective ranges at least three times as far as bear spray in calm conditions, 10 times as far during most wind conditions, and seven times as far during  cold temperatures.  Firearms are very effective at ranges less than 13 feet. 

- In cold and/or windy conditions, bear spray may need to be aimed well, much like a firearm, but without sights or ergonomic grips.

- It is easy to reload a firearm, many of which have more deterrent capacity than bear spray. 

- Firearm capacities of five to fifteen rounds are common. One round can, and often has, stopped a bear. When the bear is stopped with a firearm, it is unlikely to return, which has happened several times when bears have been sprayed with bear spray. 

-Firearms may be kept easily available in cold conditions, while bear spray is recommended to be kept warm, making it harder to access quickly. 

Firearms are, at present, considerably more ergonomic than bear spray, and much easier to practice with.  This is offset by the size of bear spray plumes. The size of the bear spray plume is much reduced at lower temperatures. 

Firearms have been shown to be extremely effective in preventing and stopping bear attacks.

Tom Smith, the lead investigator of the study, gave an interview on Alaska Public Media on October 12, 2020. In the interview, he explained it was difficult to recruit graduate students to participate in the study because it was easy to be inadvertently sprayed. He recounted how he and a graduate student were incapacitated by bear spray:

"We had a breeze that blew just the lightest cloud back at us and we blindly clawed our way into a building and we found ourselves in a women's restroom washing our faces."

If the defender is spraying into any head wind, the chances of being debilitated by the spray is significant.  If the defender has to wait until the bear is within 5-7 feet, there is very little room for error. Spray too soon, and the bear spray is blown back into your face, away from the bear. Wait too long, and you are in a deadly fight before the bear is sprayed. Once in hand to hand combat, you may or may not be able to spray the bear.

Tom Smith is optimistic about the dynamics of surprise encounters with brown bears in heavy cover:

"If push comes to shove, and, you know, you've got a can of bear spray, you're going to get the bear in the face. You may not like it being three feet away, but you're going to get it."

From my research on bear attacks, this seems overly optimistic. 

©2020 by Dean Weingarten: Permission to share is granted when this notice and link are included.

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