An Analysis of Methodologies for Assessing Grizzly Bear (Ursus Arctos Horribilis) Populations PDF Download

Author: Erin Sherry
Publisher:
ISBN:
Category : DNA fingerprinting of animals
Languages : en
Pages : 310

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Book Description
?Grizzly bears (Ursus arctos horribilis) are one of the largest terrestrial North American mammals. Once the most widespread bear species in the world, the grizzlies’ range and numbers have been reduced by fifty percent since 1890. These bears occur at low densities, are reproductively conservative, have large home ranges, and require a diversity of complex wilderness habitats where human activity is minimal. In the Banff National Park / Kananaskis Country region of southwestern Alberta, the grizzly bear has survived, albeit in reduced numbers and with continual loss of habitat. Current estimated grizzly bear numbers deviated significantly from current estimated population potential reflecting such human impacts as over-harvesting, illegal mortalities, habitat alienation, and habitat fragmentation. There is a pressing need for population inventory research. Managers lack baseline population information. Existing estimates of population parameters are unreliable, involving broad confidence limits and problems related to methods, sample sizes, and mark-recapture model biases. This study reviews methodologies for assessing grizzly bear populations and the difficulties encountered in these studies. Researchers interested in monitoring the status and trends of grizzly populations have used a variety of methods - secondhand reports, harvest data indices, bait and scent stations indices, surveys of bear sign, population modelling, direct counts, aerial surveys, and mark-recapture population studies. Each suffers from problems of assumptions, sample size, and uncontrolled variability. As Harris (1986) admits, none can be accepted unequivocally, but all approaches have some potential utility. This dissertation explores the development and application of DNA-based mark-recapture methods to evaluate a grizzly bear population in the eastern slopes of the Canadian Rocky Mountains. Forty scent station ‘hair traps’ were monitored for a total of 1328 site nights and produced 250 hair samples: 165 brown or grizzled hair samples; 74 glossy, jet black hair samples; and 11 non-bear hair samples. Of these 250 hair samples collected, 223 had intact follicles and produced DNA samples. DNA-based mark-recapture can be exploited at several levels of population monitoring resolution depending upon population investigation objectives, financial constraints, and logistical considerations. This technique can be used to provide a basic population inventory, to assess absolute abundance, to evaluate demographic processes, or to provide information on the genetic composition or biotoxin accumulation levels of a bear population. In mountainous, remote, forested regions, such as the Central Rockies ecosystem, DNA-based mark-recapture methods present a viable alternative to physical mark-recapture techniques and are superior to photographic-based mark-recapture methods. More research is required to conclusively show that DNA-based mark-recapture will provide objective and replicable estimates of grizzly bear population parameters banded by acceptable confidence limits. The problems of small sample sizes, and of mark-recapture model assumption violations due to unequal capture probabilities and lack of closure, remain intractable in this study.?--Leaf viii.