A population demography modeling tool to explore harvest management scenarios for the Fortymile caribou herd

Consulting project. Apex Resource Management Solutions for Environment Yukon

Collaborators: Leonardo Frid (Apex Resource Management Solutions Ltd.), Mike Suitor (Environment Yukon), Troy Hegel (Environment and Parks Alberta)

DG-Sim is a demographic simulation modeling tool that allows caribou managers to explore alternative harvest scenarios while explicitly accounting for uncertainties. The goal is to allow stakeholders to consider the risks and trade-offs associated with different harvest levels, and to identify uncertainties with a large influence on the projected population trajectory. The Fortymile caribou herd (FMCH) ranges across east-central Alaska, USA, and as far as the west-central Yukon, Canada. This herd has a history of rapid decline from approximately 50,000 to 6,000 individuals between 1963 and 1973, followed by a subsequent recovery to approximately 71,000 individuals in the most recent 2017 photo census. Given recent population increases, there is pressure from some stakeholders to increase harvest rates, while others argue for caution. We analyzed available fecundity and survival data using Bayesian generalized linear mixed models, accounting for trends, inter-annual variability, and correlations in parturition rate among age classes. We sampled DG-Sim model parameters from the Bayesian posterior probability distributions to project population trajectories retrospectively and prospectively. DG-Sim is designed to facilitate the exploration and summary of many alternative harvest scenarios. Population projections from these scenarios can be used to inform discussions of FCMH harvest policy among stakeholders.