Using incidental mark-encounter data to improve survival estimation

1. Obtaining robust survival estimates is critical, but sample size limitations often result in imprecise estimates or the failure to obtain estimates for population subgroups.  Concurrently, data are often recorded on incidental re-encounters of marked individuals, but these incidental data are often unused in survival analyses.

2. We evaluated the utility of supplementing a traditional survival dataset with incidental data on marked individuals that were collected ad-hoc.  We used a continuous time-to-event exponential survival model to leverage the matching information contained in both datasets and assessed differences in survival among adult and juvenile and resident and translocated Mojave desert tortoises (Gopherus agassizii).

3. Incorporation of the incidental mark-encounter data improved precision of all annual survival point estimates, with a 3.4–37.5% reduction in the spread of the 95% Bayesian credible intervals.  We were able to estimate annual survival for three subg...