Modeling in Support of Adaptive Management of the Rocky Mountain National Park Elk Population, 2014 - 2019

Hobbs, N; Abouelezz, Hanem

EXECUTIVE SUMMARY: We used a Bayesian hierarchical model of population dynamics of the Rocky Mountain National Park elk (Cervus elaphus) population on winter range to support decision on culling needed to implement the Elk and Vegetation Management Plan during 2014 - 2019. The model assimilates four time series of data: aerial counts, ground counts, sex and age classifications, and annual harvest outside the park to fit a matrix population model with three sex and age classes. Modeling revealed a clear downward trend in elk numbers during the last decade, from more than 500 individuals to fewer than 200. Annually increasing levels of female harvest outside the park during 2010 to 2019 contributed to this trend, but migration from the park to winter range at lower elevations likely accelerated the decline in numbers of elk using the park during winter. The growth rate of the population in 2019 in the absence of harvest or emigration was 1.1, indicating a potential for strongly positive growth, 10% per year or more. We found no evidence that elk needed to be culled to meet the population objectives set in the Elk and Vegetation Management plan, 600 - 800 animals. The probability that the population would exceed the upper limit of this range was essentially zero of all years of the study and the probability that the population was less than 600 was essentially one. The model allows hard-won data to inform a critical policy decision in the park in a way that is honest about uncertainty.

Modeling in Support of Adaptive Management of the Rocky Mountain National Park Elk Population, 2014 - 2019

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