How many grizzlies are left in Alberta? This is the question that will be on the minds of many as the conclusion to the province’s grizzly DNA census project is within sight. We may have to wait a little longer given the Ministers untimely announcement that anecdotal evidence may be considered as well. For more on the Minister’s plans read Stick to the Science – link here).

From the DNA data gathered so far we already know the number is low. Far lower than most anticipated. With the data from BMAs (Bear Management Area) north of Highway 16 soon to be added to the census, the most recent projection puts the number at 400 adult grizzlies roaming the foothills, eastern slopes of the Rockies, or the northwest corner of the province.

Since we’re hopefully getting closer to the announcement of what I’m now calling the number… I’m interested in another number.  To me a far more optimistic number.  A far more controversial number: How many grizzlies can Alberta support? If the census population number is accepted as credible and/or reliable, then a carrying capacity can be derived and added as an objective to the Alberta Grizzly Recovery Plan (link to a PDF copy here). Of course there will be considerable push back and challenges to the number regardless of what it actually is resulting in several delays, further study (already recommended within the Recovery Plan), and well more politicking at the expense of the grizzly. The Alberta Grizzly Bear Recovery Plan does not offer a target recovery population number claiming:

Grizzly bear population trend should increase over time towards carrying capacity. However, evaluating this measure is currently limited by lack of a reliable population estimate and carrying capacity (see Objective 2), and requires repeated population surveys over time. In addition, due to the slow reproductive rate of grizzly bears, it will take considerable time for the population to increase. Although an increasing population trend is an important measure of success, it will take a minimum of five years to produce a preliminary estimate of trend according to the proposed DNA inventory.

Recovery plans generally identify population targets, but setting a population target for grizzly bears in light of insufficient data would be misleading. Identifying a realistic population target, based on current and reliable data, is the first step towards achieving a population goal.

I’m fairly certain given the amount of study within past 5 years determining grizzly populations and habitat suitability that a carrying capacity for the province has already been at least estimated by Recovery Project researchers. Even if they’ve already ‘done the numbers’ they aren’t sharing and it would appear that it may take several years based on the methodology within the Recovery Plan using trending data to determine a population target. Well I can’t wait that long… I’ve taken a crude, possibly “misleading”, attempt at determining the Provincial population target using Banci’s 1990/91 data regarding population density in defined Grizzly Bear Zones combined with Kansas’s interpretation of Banci’s work as it relates to Alberta and came to an initial number of between 1,788 and 1,999 grizzlies. Factoring in habitat degradation and loss since the time of Banci’s work I’ve discounted the lower estimate by 41% – the approximate human population growth of Alberta since 1991. Therefore my estimate at Alberta’s carrying capacity is between 1,055 and 1,999 grizzly bears – ‘click’ on the table below to see a larger image.

Nearly two thousand grizzlies is somewhat optimistic considering habitat already lost. However, I chose not to discount the maximum 1,900 population figure as Kansas includes north eastern Alberta (BMA 16) as part of his study for a total 332,279 sq. km of suitable habitat versus the 228,000 sq. km cited within the Recovery Plan. Further if the Recovery Plan succeeds there is some evidence that habitat reclamation is possible and beneficial to the grizzly.

Let’s call it a day and make it an even 2,000!

Leave a Reply

You must be logged in to post a comment.