Abstract 176 – A Unified Approach to Long-Term Population Monitoring of Grizzly Bears in the Greater Yellowstone Ecosystem

Matthew Gould, Justin G. Clapp, Mark A. Haroldson, Cecily M. Costello, J. Joshua
Nowak, Hans W. Martin, Michael R. Ebinger, Daniel D. Bjornlie, Daniel J. Thompson, Justin A.
Dellinger, Matthew A. Mumma, Paul M. Lukacs, Frank T. van Manen

A challenge for long-term wildlife research and monitoring programs is maintaining a cohesive
monitoring system. Interruptions or changes in data collections can reduce compatibility of
data sets. Integrated population models (IPMs) can address these limitations by combining data
sources that may be temporally disjointed into a unified statistical framework while providing a
holistic view of population dynamics. We developed an IPM in a Bayesian framework for grizzly
bears (Ursus arctos) in the Greater Yellowstone Ecosystem. We coupled demographic data with
multiple, independent, and temporally disjoint population count data to link annual changes in
population size with vital rates over 4 decades (1983–2022). Parameter estimates indicated
survival of bears ≥2 years of age was high, contributing to robust population growth during the
1980s and 1990s (λ = 1.030–1.058). A slowing of population growth started around 2000
(2000s: λ = 1.023) and continued into the 2010s (λ = 1.009), due primarily to reductions in
survival of bears <2 years of age. These findings corroborate previous research that identified
density-dependent effects as a likely cause. The IPM framework provided greater certainty and
understanding regarding the dynamic demographic characteristics of the grizzly bear
population and serves as a powerful monitoring tool for this long-lived species. Through
implementation of the IPM, we can now disseminate timely information and inference to help
inform adaptive management strategies and policy decisions necessary for the continued
management and conservation of this population. This robust and flexible monitoring system
allows us to investigate the effects of a changing ecosystem on population dynamics,
incorporate new data sources and statistical models, and respond to changes in monitoring
needs for the population.