Grizzly Bear Demographics in and Around Banff National Park and Kananaskis Country, Alberta

Abstract

The area in and around Banff National Park (BNP) in southwestern Alberta, Canada, is 1 of the most heavily used and developed areas where grizzly bears (Ursus arctos) still exist. During 1994-2002, we radiomarked and monitored 37 female and 34 male bears in this area to estimate rates of survival, reproduction, and population growth. Annual survival rates of bears other than dependent young averaged 95% for females and 81-85% for males. Although this area was largely unhunted, humans caused 75% of female mortality and 86% of male mortality. Females produced their first surviving litter at 6-12 years of age (x -= 8.4 years). Litters averaged 1.84 cubs spaced at 4.4-year intervals. Adult (≥6-years-old) females produced 0.24 female cubs per year and were expected to produce an average of 1.7 female cubs in their lifetime, based on rates of reproduction and survival. Cub survival was 79%, yearling survival was 91%, and survival through independence at 2.5-5.5 years of age was 72%, as no dependent young older than yearlings died. Although this is the slowest-reproducing grizzly bear population yet studied, high rates of survival seem to have enabled positive population growth (λ = 1.04, 95% CI = 0.99-1.09), based on analyses using Leslie matrices. Current management practices, instituted in the late 1980s, focus on alleviating human-caused bear mortality. If the 1970-1980s style of management had continued, we estimated that an average of 1 more radiomarked female would have been killed each year, reducing female survival to the point that the population would have declined. JOURNAL OF WILDLIFE MANAGEMENT 69(1):277-297; 2005

Overestimates of maternity and population growth rates in multi-annual breeders

“…These simulated results are consistent with the empirical data reported by Garshelis et al (2005). They used the unbiased M4 method and reported an unexpectedly low Mx compared to other North American grizzly bear populations (0.24 vs. 0.32).…”

“…They attributed their relatively low value of Mx due to some combination of real biological differences and/or bias in the other studies. We concur with Garshelis et al (2005) that they found an unexpectedly small Mx and that the differences in estimated Mx were substantial-but the evidence presented here suggests that the main cause may be bias in other studies using the biased method M3 (Eberhardt et al 1994;Hovey and McLellan 1996;Miller 1997), not an abnormally small Mx in their study area. We suspect that estimates of Mx reported in the literature using method M3, including our own previous work , may be biased overestimates.…”

“…Schwartz and White (2008) recognized the bias of McLellan (1989) methods and proposed a completely different approach through computing transition probabilities between female states defined as female alone, with cubs, yearlings, or 2-year olds. Garshelis et al (2005) mentioned the potential bias in the standard method (only 13 birth intervals were closed compared to 23 open-ended intervals in their study), and they calculated Mx by proposing an alternative method (labeled M4) which is to divide each year the number of offspring by the number of females and then to compute the arithmetic mean over years. They found that their estimate of grizzly bear Mx was also among the lowest ever recorded and attributed that to some combination of real biological differences and/or biased overestimates in other studies.…”

“…As a consequence, seven females (#1, #3, #4, #8, #10, #11, and #12) are not included, and the Mx estimate uses only data from five of the 12 females in our sample-similar to the proportions (1/2) reported by Hovey and McLellan (1996) and (1/3) Garshelis et al (2005). As precised by McLellan (1989), the standard method M3 uses more data, because all litter size data could be used to compute mean litter size; however, seven females are still excluded to compute mean interbirth interval.…”

Interdisciplinary problem solving workshops for grizzly bear conservation in Banff National Park, Canada

“…Benn and Herrero (2005) found that 119 of 131 recorded grizzly bear mortalities in Banff National Park and the adjoining Yoho National Park in the period 1971-1998 were due to human-related causes, and that ''all 95 humancaused mortalities with known accurate locations were within 500 m of roads or 200 m of trails' ' (p. 63). Intensive management and frequent interventions to move or protect individual bears have improved the survival rate for grizzlies in Banff National Park in recent years, but humans are still the primary cause of death (Garshelis et al 2005a).…”