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 Interagency Grizzly Bear Committee (I&E Subcommittee)
Questions and Answers about Grizzly Bear Population Augmentation
Introduction:
Small populations of grizzly bears face demographic challenges as well as genetic issues associated with isolation or very limited gene pools. Augmenting these small populations with grizzly bears from larger, more stable populations is one management option to increase numbers and to maintain genetic diversity. Grizzly bear augmentation can be a contentious public issue due to concerns about human safety and the effects of a recovering population on local economies and recreation. Developing a strategy for increasing understanding and acceptance of grizzly bear population augmentation is a goal of the Interagency Grizzly Bear Committee (IGBC).
What do you mean when you say population augmentation?
Population augmentation is a management activity through which animals are added to an existing population to bolster numbers or provide more varied genetic material. Wildlife management in North America includes numerous examples of trapping and transplanting animals to assist other populations. For instance, elk transplants from Yellowstone National Park have benefited numerous elk herds in several western states. Augmentation should not be confused with reintroduction. Reintroduction refers to placing animals into areas where the original population has been lost or suitable habitat occurs that has not held a population in recent history whereas augmentation seeks to bolster an existing population.
I have heard of nuisance grizzly bears being relocated. Is that an example of augmentation?
Grizzly bears are occasionally relocated to remove them from a site where they have obtained garbage, human or animal foods, killed livestock, or for other reasons. Relocations should not be confused with augmentation. These management actions are an attempt to separate the animal from a problem situation. Population augmentation generally involves bears with no record of conflicts with humans, typically young bears (3-6 years old) being moved into a population that may benefit from increased numbers or new genetic material. Young bears may more readily adapt to new habitat and be less likely to leave the augmentation area.
Has population augmentation of grizzly bears occurred?
The only instance of grizzly bear population augmentation in North America occurred in the Cabinet Mountains of northwest Montana and northern Idaho. The Cabinet Mountains grizzly bear population was estimated to contain 15 or fewer bears in 1989 and was expected to disappear in the next several decades unless some action was taken. A test of population augmentation was proposed and 4 young female grizzly bears were added to the area between 1990 and 1994. All of the bears came from the backcountry of southeast British Columbia and had no history of conflicts with humans. Bears were released in July when food supplies in the form of huckleberries were developing and all wore radio collars for monitoring. Two criteria of success were established before augmentation occurred: 1) the bears must remain in the target area for at least one year as a short term goal, and 2) the bears should reproduce. Three of the four bears remained in the area for one year. One of the bears died after the first year but there was no evidence of any human involvement in her death. The fourth bear left the area, but was recaptured and released again in the Cabinet Mountains. Radio collars were designed to drop off after 1-2 years because the young bears were still growing and collars tight enough to stay on at the time of their release would become restrictive and dangerous to the bears as they grew. Grizzly bears typically do not reproduce until the age of 6 years-old and none of these animals had produced young during the monitoring period prior to their capture and release. Attempts to recapture the animals were not successful but hair snagging and DNA analysis 10 years after the last bear was released has demonstrated that at least one of the four original transplants remains and has produced offspring. Genetic evidence indicates that her offspring have also reproduced. During 2005 and 2006 two additional female grizzly bears were transplanted to the Cabinet Mountains in continuation of this program.
Is grizzly bear population augmentation going to occur elsewhere in North America?
Augmentation was suggested as an alternative to be considered for the North Cascades grizzly bear population in the State of Washington. An environmental impact statement and public comment must occur as part of the evaluation of this alternative. Augmentation is also being considered by the British Columbia government for the British Columbia portion of the North Cascades grizzly bear population.
What would be the source for bears involved in future augmentation efforts?
Bears used in population augmentation might come from various places, but the donor population must be large enough to absorb the losses of these individuals. We believe that augmentation efforts would have the best chance of success if bears came from places with similar foods and habitat to the target area.
What are the criteria used to select appropriate grizzly bears for augmentation programs?
Grizzly bears used in previous augmentation efforts have typically been younger animals (3-6 years of age) that may be more adaptable to a move. Older animals are thought to be more likely to return to their area of origin or wander extensively. Females have been the first choice in previous augmentation efforts because of their reproductive contribution, however males may be appropriate candidates and will increase genetic diversity of the target population when they reproduce with resident females. No bears used in augmentation efforts have had any history of conflicts with humans, and nuisance grizzly bears should not be used in augmentation.
What happens to existing grizzly bear populations if we don’t augment them?
Small grizzly bear populations that are not augmented may persist for several years but are expected to eventually disappear. Low reproductive rates and insufficient reproduction to replace lost animals, coupled with inbreeding effects on the genetics of small populations are expected to cause decline and eventual extirpation.
What are the benefits to humans of a successful augmentation program?
Augmentation is one of the tools in successful grizzly bear recovery efforts. A successful augmentation program will reduce the chances of a population being extirpated and will help achieve recovery and delisting sooner. A larger, healthier grizzly popualion means less need for restrictive management and will increase management flexibility.
Some reference on augmentation
Servheen, C. W. Kasworm and T. Thier. 1994. Transplanting grizzly bears as a management tool: Results from the Cabinet Mountains, Montana. Biological Conservation. 71:261-268.
Kasworm, W., T. Their, and C. Servheen. 1998. Grizzly bear recovery efforts in the Cabinet/Yaak ecosystem. Ursus. 10: 147-153.
Proctor, M. F., C. Servheen, S. D. Miller, W. F. Kasworm, and W. L. Wakkinen. 2004. A Comparative analysis of management options for grizzly bear conservation in the US-Canada trans-border area. Ursus. 15: 145-160.
Kasworm, W, M. Proctor, C. Servheen and D. Paetkau. 2007. Success of grizzly bear population augmentation on Northwest Montana. Journal of Wildlife Management. 71:1261-1266.
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