| Grizzly bears in Banff, Kananaskis Country and surrounding areas have a much lower reproductive rate than other bear populations that have been studied in North America.
And the low birth rate means the area’s grizzly population is particularly vulnerable, making any bear deaths cause for concern in terms of the long-term sustainability of the population.
That’s one of the major findings of the Eastern Slopes Grizzly Bear Project, an 11-year research project that studied the cumulative effects of development on grizzly bears along the Central Rockies ecosystem. Scientists spent nine years studying radio-collared bears in the Bow River watershed and the last two years analyzing the data. A final report on the project will be released this spring.
Project director and biologist Steve Herrero says the research showed that grizzly bears in the Bow River watershed had the lowest reproductive output of 25 bear populations that have been studied in North America. Researchers discovered grizzlies in the Banff and Kananaskis areas weren’t having cubs until they were an average of eight years old, there was an average of four and a half years between litters, and the average litter was less than two cubs. Herrero says in other bear populations in habitat where food sources are more abundant, female grizzlies had bear cubs at an average age of 6.5 years, the time span between litters was an average of 2.8 years, and the average litter size was 2.35 cubs .
"Some other (grizzly bear) populations were twice as productive," says Herrero. "That’s important because it means if our population is depressed it will recover very slowly…. It shows the vulnerability of this population."
Despite the low birth rate, research showed that bear populations in the study area actually increased between 1994 and 2002 by about four per cent each year. Herrero attributes the increase to good bear management in the park. However, he says increased human grizzly interaction will make it hard to maintain the trend.
Herrero says in order for grizzlies to continue to have a sustainable population in the Banff and Kananaskis areas, a 91 per cent survival rate is required for female grizzlies. In 2003, the female grizzly survival rate was 88 per cent and in 2004 it was 71 per cent, which could indicate grizzly populations are starting to decline since the project team’s field research concluded, he says.
Researchers found there were 39 grizzly deaths between 1993 and 2002, and 34 of those deaths were caused by human activity. For example, 13 "problem bears" had to be put down or relocated between 1993 and 2002, and six grizzlies were killed on the highway or by trains.
Herrero says preventing bear deaths is a huge challenge because the Bow River watershed is one of the most developed areas of the world where grizzly bears survive. Research showed that Canmore and Lake Louise are both "mortality sinks" for grizzly bears.
As new development occurs in the Bow River Valley between Banff and Dead Man’s Flats, Herrero predicts there will be more conflicts between bears and humans and that will stress the bear population.
"It will probably take an exceptional effort to make sure we maintain grizzlies into the future," he says.
Herrero will make a presentation on the results of the Eastern Slopes Grizzly Bear Project on January 10 at 7:30 p.m. at the Calgary Zoo. |
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