  The natural subgroups often seen in mark-recapture studies and the complexity
of real mark-recapture data means that parametric and discrete style models can
be insufficient. Non-parametric models avoid these often restrictive
assumptions. We consider the non-parametric Dirichlet process for modelling
latent individual heterogeneity in probability of observation and the
probability of remaining in or out of a marine sanctuary. Simulation studies
demonstrated accurate estimation of multiple groups of latent individual
heterogeneity. Simulations were also used to identify the limits of the
Dirichlet process. The ability of the Dirichlet process to pick up unimodal
heterogeneity was explored in order to avoid potential spurious multimodality.
In application to a subset of the data from the North Atlantic humpback whales
we were able to estimate annual population-level variation in usage of the
marine sanctuary and three measures of individual-level variation. With the
Dirichlet process prior we were able to detect multimodality in each parameter.
