openpopulation

Openpopulation is a framework in population ecology and wildlife management describing populations in which individuals can enter by birth or immigration and can leave by death or emigration between sampling occasions. This contrasts with closed-population models that assume no births, deaths, or movements during the study period. Open-population models aim to estimate demographic parameters such as survival, recruitment, and migration probabilities from longitudinal capture–recapture data.

Prominent open-population models include the Cormack–Jolly–Seber (CJS) models, which estimate survival and capture probability for individuals observed across multiple occasions, and the POPAN formulation, which parameterizes a superpopulation to directly estimate the total number of individuals that could appear during the study. The framework accommodates time- and individual-variation in capture, survival, and movement, including temporary emigration.

Parameter estimation relies on maximum likelihood or Bayesian methods. Analyses typically use mark-recapture data collected over several sampling occasions, often with marked animals observed and re-sampled. Software tools such as MARK and related interfaces implement open-population models and support model selection, goodness-of-fit checks, and handling covariates.

Applications span wildlife management, conservation planning, and ecological research. Open-population models have been applied to birds, mammals, marine species, and amphibians to inform population size, survival rates, and recruitment under changing environmental conditions. Limitations include potential tag loss, misidentification, heterogeneity in capture probabilities, and violations of model assumptions; robust-design approaches help mitigate some issues.