Age–dependent capture–recapture models and unequal time intervals

• Published in: Animal biodiversity and conservation Vol. 42; no. 1; pp. 91 - 98
• Main Authors: Sanz–Aguilar, A., Pradel, R., Tavecchia, G.
• Format: Journal Article
• Language: English
• Published: Barcelona Museu de Ciencies Naturals 01-01-2019; Museu de Ciències Naturals de Barcelona
• Subjects: Age; age–dependent models; Biodiversity and Ecology; Capture-recapture studies; capture–mark–recapture; Computer simulation; Environmental Sciences; Estimates; Intervals; missing data; Natural populations; Survival; survival probability; Missing data; Capture–mark–recapture; Survival probability; Age–dependent models
• ISSN: 1578-665X; 2014-928X
• DOI: 10.32800/abc.2019.42.0091

Estimates of survival probabilities in natural populations can be obtained through capture–mark–recapture (CMR) models. However, when capture sessions are unevenly spaced, age–dependent models can lead to erroneous estimates of survival when individuals change age class during the time interval between two capture occasions. We propose a solution to correct for the mismatch between time intervals and age class duration in two age class models. The solution can be implemented in different ways. The first consists of adding dummy occasions to the encounter histories and fixing the corresponding recapture probabilities at zero. The second makes use of the log–link function available in some CMR software (e.g. program MARK). We used simulated and real data to show that the proposed solution delivers unbiased estimates of age–dependent survival probabilities.