| Summary: | Decreasing numbers of moulting common seals in Scotland have prompted concerns about the state of the population. Proximately, the observed declines could be due to changes in 1) fecundity, 2) mortality or 3) the timing of moult in relation to the aerial surveys. It is essential that the relative contribution of these factors is evaluated in order to isolate the possible ultimate causes of the observed decline. We adapt a Bayesian model of UK common seal dynamics to enable it to fit detailed pupping and moulting data collected in the Morray Firth, Scotland. This work confirms that the decline is not a survey artifact. Furthermore, use of these more detailed data considerably improves the model’s ability to identify the possible demographic causes of the decline, resulting in only two alternative demographic scenarios.
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