Modeling structured population dynamics using data from unmarked individuals

Abstract/Summary

The study of population dynamics requires unbiased, precise estimates of
abundance and vital rates that account for the demographic structure inherent in all wildlife
and plant populations. Traditionally, these estimates have only been available through
approaches that rely on intensive capture–recapture data. We extended recently developed Nmixture
models to demonstrate how demographic parameters and abundance can be estimated
for structured populations using only stage-structured count data. Our modeling framework
can be used to make reliable inferences on abundance as well as recruitment, immigration,
stage-specific survival, and detection rates during sampling. We present a range of simulations
to illustrate the data requirements, including the number of years and locations necessary for
accurate and precise parameter estimates. We apply our modeling framework to a population
of northern dusky salamanders (Desmognathus fuscus) in the mid-Atlantic region (USA) and
find that the population is unexpectedly declining. Our approach represents a valuable
advance in the estimation of population dynamics using multistate data from unmarked
individuals and should additionally be useful in the development of integrated models that
combine data from intensive (e.g., capture–recapture) and extensive (e.g., counts) data
sources.