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 The objective of this research is to develop and evaluate methods for more effectively monitoring use of sites where wildlife populations seasonally aggregate. Examples of such sites include traditional haul-out sites used by Pacific walruses and streams where brown bears aggregate to feed on spawning salmon. Agencies often monitor use of these sites by obtaining as many counts as possible during each aggregation period and informally tracking summary statistics such as seasonal maximums. However, counts at these sites tend to be highly variable and resulting trend estimates typically have poor precision.
We have been developing and evaluating formal approaches for monitoring trends at aggregation sites using historical data to model within-season patterns of use, deriving effective model-based monitoring statistics, and using model-based simulations to develop optimal sampling designs. We have also been investigating the potential for using generalized mixed models and empirical Bayesian techniques to efficiently model within-season patterns in cases where some years, by themselves, lack sufficient data. Our current research focuses on further development of these approaches and development of specific protocols for monitoring and estimating trends in walrus and brown bear populations. Results will also provide new, more effective, general approaches for monitoring trends in a wide variety of other wildlife populations that periodically aggregate at predictable locations.
Udevitz, M. S. 1999. Modeling variability in replicated surveys at aggregation sites. Pages 167-177 in G. W. Garner, S. C. Amstrup, J. L. Laake, B. F. J. Manly, L. L. McDonald and D. G. Robertson, eds. Marine mammal survey and assessment methods. A. A. Balkema, Rotterdam, Netherlands.
Udevitz, M. S., C. V. Jay, and M. B. Cody. 2005. Observer variability in pinniped counts: ground-based enumeration of walruses at haul-out sites. Marine Mammal Science 21(1):108-120.
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